M£GO02 J*i Movember 1978 Government of India „,„, ATOMIC ...
280
M£GO02 J*i RRC-25 t Movember 1978 Government of India „,„, ATOMIC ENERGY COMMISSION ACTIVITY REPORT 1 97B Edited by G. Ananthakrishna, N. Ramanathan, P. Rodriguez, R. Shankar Singh and S. Venkataraman Reactor Research Centre Kalpakkam 603 102 Tamil Nadu, India
Transcript of M£GO02 J*i Movember 1978 Government of India „,„, ATOMIC ...
M £ G O 0 2 J*i
R R C - 2 5
t Movember 1978
Government of India „,„, ATOMIC ENERGY COMMISSION
ACTIVITY REPORT 1 97B
Edited by
G. Ananthakr ishna, N. Ramanathan, P. Rodriguez,
R. Shankar Singh and S. Venkataraman
Reactor Research Centre Kalpakkam 603 102 Tamil Nadu, India
GOVERNMENT OF INDIA
ATOMIC ENERGY COMMISSION
ACTIVITY R E P O R T 1976
Edi ted by
G. Ananthakr i shna , N. Ramanathan , P . Rodriguez R. Shankar Singh and S. V e n k a t a r a m a n
REACTOR RESEARCH CENTRE
KALPAKKAM 603 102
TAMILNADU, INDIA
C O N T E N T S
REACTOR PHYSICS 1
REACTOR DESIGN 38
REACTOR ENGINEERING 45
DESIGN OF SODIUM CIRCUITS 61
REACTOR F U E L HANDLING 68
ELECTRICAL AND INSTRUMENTATION
ENGINEERING FOR F B T R 71
DATA PROCESSING SYSTEM FOR F B T R 85
REACTOR OPERATION STUDIES 89
REACTOR CHEMISTRY 92
REACTOR CONSTRUCTION 12 3
MATERIALS SCIENCE 12 9
METALLURGY 167
REPROCESSING 229
INSTRUMENTATION 242
SAFETY RESEARCH 259
ENGINEERING SERVICES 2 72
E r r a t a 277
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1. REACTOR PHYSICS
1.1 Burn-up Code in X-Y Geometry - BIRAVI (L. Srinivasan)
A multigroup diffusion - burnup code in X-Y geometry was
developed" to carry out burnup calculation in fast reac tors and extend it
to do fuel management studies. The idea of developing this code was to
have a code which can do both diffusion and burnup calculations in suc
cession with a short computer time with reasonable accuracy necessary
for fuel management studies. Many of the existing codes use finite dif
ference methods to solve the diffusion equation and take large amount
of computer t ime. The code BIRAVI solves the diffusion equation using
the principles of variational calculus and expanding the flux in t e rms of
trigonometric se r ies . The burnup part is solved by the usual finite dif
ference method.
The code was tested for a sample problem. The axial buckling
was chosen appropriately to get the same K as obtained with R-Z
code. Four neutron energy groups were considered for the calculation
and the burnup in the core and blanket of the given system was calcu
lated. The flux distribution, the average flux in different burnup regions
and the total burnup were found to be in agreement with those obtained
in the midplane from the French code REVE . The total time con
sumed for one diffusion calculation and burnup calculation was about 2
mins only on IBM-370 computer, as compared to about 4 mins required
by REVE for the same calculation.
REFERENCE
l . R . B r u y e r e , P. Quilichini and F.Richaud, "Specification d'un Code
d'Evolution en Geometrie RZ-Code REVE", Rapport D. C . E . -
Ca. n° 056 (1968).
- 2 -
1.2 Heterogeneity Calculations in Fas t Reactor Lattices. (J.V. Muralidhar Rao, S.M.Lee and R. Shank ar Singh) T
Design calculations for fast power reactors are generally made
assuming the reactor core to be homogenous. We have attempted to
estimate the heterogeneity effect in an oxide fuelled LMFBR of 500
MWe output. Since the heterogeneity effect is small , we have relied
on perturbation methods for its estimation. Storrer has proposed a
perturbation method based on the collision probability equation and the
experience with this method in estimating the heterogeneity effects has
been encouraging
(3) We have developed a code based on S tor re r ' s formulation.
This code was tested with the results of ZPR-III criticality measure
ments . Then calculations were made for FBR-500 to estimate the
spatial heterogeneity effect on K and it was found to be quite small 611
varying from 44 pcm to 88 pcm as the pin diameter is varied from
4.25 mm to 17 mm.
REFERENCES
l . F . Storrer and A. Khairallah, Nucl. Sci. & Engg.,24-,153 (1966).
2. A. Khairallah, T. Lacapelle and F . Storrer , Proc. Symp. Fas t
Reactor Physics, Karlsruhe, 1967, Vol. II, IAEA, Vienna (1968).
3. J .V . Murtl idhar Rao, S.M.Lee and R.Shankar Singh, "Theory
and Input Specifications for the Code VANI", RRC-FRG Note
under preparation.
- 3 -
1. 3 Modificatio_ns ..to the Code MUDE (T.M.John and S.M.Lee)
( 1 2 ) The one dimensional diffusion theory code MUDE ' was.modi-
fied to increase its capability. The code now has the following additional
capabilities:
a. Power shape calculations can be performed during concentration
searches for a multizone core. An under relaxation was incor
porated in the iteration for power and enrichment. This was
found to give a very quick convergence.
b . Source calculations can be performed in subcrit ical systems.
The new routines were checked against analytical solution for a
simple problem and the agreement was excellent. It is found
that scaling up the flux after each iteration by a factor
W= i/Ll- CTV*V-J S,H dv>/J St**!
th where S = i: iteration fission source
n
S = external source density ext J
gives fast convergence even for nearly crit ical systems.
c. An option has been introduced to print out groupwise contribu
tion of the delayed neutrons from each isotope to the total effec
tive delayed neutron fraction.
d. An option to execute a sequence of problems in the same step
without repeating the data cards has been introduced. This
option is useful in parametr ic studies where only few data chan
ges ar made between problems.
e. A separate version of the code has been prepared which is
coupled to a thermal hydraulic code so that optimisation of
engineering parameters can be done at a single stretch.
- 4 -
REFERENCES
1. T. M. John, "MCf.E-A One Dimensional Diffusion Theory
Neutronics Code", RRC-FRG/RP-60 (1975).
2. C. Bore, Y. Dandeu and C. Saint Amand, "Resolution de l'Equation Multigroupe de la Diffusion Dans une Geometrie a une Dimension et Calculs Annexes: Code MUDE", CEA-R 2923 (1965).
1. 4 Modifications to the Two-Dimensional Perturbation Theory Code PERTALCI (S. Krishnan)
PERTALCI is a two-dimensional perturbation theory code utili
zing previously calculated fluxes and adjoint fluxes. The code originally
developed at Cadarache , France , was adapted for usage on the IBM-
370/155 computer .
Numerous modifications have been incorporated in the adapted
version. Dynamic dimensioning capability of Fortran-IV language has
been included to remove the upper limits on the problem paramete r s .
Normalization options were included in the reaction ra te t r averse rou
tines. Option for the exact perturbation theory calculations has been
also made available. Modifications in the B computing routines are
being made to have delayed neutron yield as the starting data ra ther
than the delayed neutron fractions of the nuclei. Attempts are also be
ing made to make use of the delayed neutron group spectra ra ther
than the mean energy of the groups. Routine to convert the reactivity
coefficients from units to Inh units is also being included.
REFERENCES
1. R .Bruyere and P. Quilichnini, "557-S: Depouillement d'ALCl",
Rapport D . C . E / C a n° 060 (1969).
2. S. Krishnan, "Specifications for the Perturbation Code
PERTALCI", RRC-FRG/RP-81 (1975).
- 5 -
232 1. 5 Evaluations of Stat is t ical Resonance Paramete r s for Th in 4 to
5 0 keV Energy Region (S. Ganesan)
Neutron-induced reaction ra tes in the unresolved resonance region
are of fundamental importance in calculating important integral parame
te rs such as K breeding rat io and reactivity coefficients of large fast
power reactor systems. For thorium fuelled fast r eac to r s , the evaluation 2 32
of s tat is t ical resonance parameters for' Th is thus of great importance.
Using the code ADDJA we have evaluated (based on the s tat is t ical
approach) the p wave strength function as a function of energy for a broad
group structure corresponding to the c ross-sec t ions recommended in the
ENDF/B-IV l ibrary. A compilation of the mean resonance parameters 2 32 reported by different evaluators and u se r s for Th has been made and
the effect of these different sets of mean resonance parameters on the (2)
infinite dilution c ross sections has been investigated '. The sensitivity
of adjusted p wave strength function corresponding to the uncertainties in
the values of s \ .ve strength function, s and p wave level spacing and
e-(2)
(2) the n u c l e a r r a d i u s was s tud ied . After evaluat ing a s e t of m e a n r e
sonance p a r a m e t e r s for use in r e a c t o r ca l cu la t ions , we r e c o m m e n d (3> that the th ick s a m p l e t r a n s m i s s i o n and self indica t ion m e a s u r e m e n t s
232 be p e r f o r m e d for Th in o r d e r to d e t e r m i n e e x p e r i m e n t a l l y the m e a n
r e s o n a n c e p a r a m e t e r s in the u n r e s o l v e d r e s o n a n c e r eg ion .
REFERENCES
1. S. Ganesan, Atomkernenergie 29, 14 (1977).
2. S. Ganesan, "Evaluation of Statistical Resonance paramete rs 232
for Th in 4 to 50 keVEnergy Region" (To be published).
3. T. Y. Byoun, R. C. Block and T. Semler, Meeting on New
Developments in Reactor Physics and Shielding Calculations,
Lake Kiamesha, N. Y. , 12-15 September 1972, (CONF-720901).
T 6 -
1. 6 Generation and Evaluation of Self-shielded Cross Sections for Nickel (S. Ganesan, M. L.Sharma, A. M. Manekar, R. Venkatesan, S .M.Lee and R. Shankar Singh)
Work on updating of nickel c ross sections was taken up because
of certain discrepancies noticed in these cross section data in the analysis of
of cr i t ical assemblies . Another reason was the conspicuous lack of self-
shielding factor data for this mater ia l in the Cadarache Cross Section
Library available at RRC. Latest resonance parameter data for all the • + * • i •••, AT-58 »T-60 „ .6 l ^T.62 , AT.64 .. ",(1,2)
five isotopes of nickel Ni , Ni , Ni , Ni and Ni were compiled (3)
These data were then processed with code DOPSEL to generate tempera ture and composition dependent self shielding factors and infinite dilu-
(4) tion cross sections in a suitable format for further analysis and testing
and were stored on a magnetic tape.
To evaluate this data, analysis of integral experiments has
been taken up. Two reac tors have been chosen for this analysis.. ZPR-
6-6A and RAPSODIE (Fortissimo). The integral parameters considered
are K central worths and reflectivity worths. It should be noted that
both the reac tors chosen have predominantly nickel ref lectors . Analysis
of the correlat ions of calculated integral parameters against their
measured values is in p rogress .
REFERENCES
1. M. C. Moxon, "Neutron Cross Sections of Natural Nickel and its
Isotopes below Neutron Energy of 600 keVH, AERE-R-7568 (1974).
2. S .F . Mughabghab and D. L. Garber, "Neutron Cross Sections",
BNL-325 (1973).
3. S. Ganesan, P. Bhaskar Rao and R. Shankar Singh, "Computer
Code DOPSEL", RRC-6 (1975.),.
4. R. Venkatesan, A. M. Manekar and S. Ganesan, "Generation of
Self-shielded Multigroup Cross-sect ions for the Isotopes of
Nickel", RRC-FRG/RP-102 (1976).
- 7 -
1. 7 Generation of Self Shielded Cross Sections for Fe , Cr, Ni and the Study of their Contribution to Doppler Effect in Fas t Power Reactors (M. L. Sharma and S. Ganesan)
The Doppler Coefficient of reactivity is the only prompt r eac t i
vity coefficient in the consideration of the safety aspects of large fast
power reac tors during rapid power t ransients . Recently the delayed
negative reactivity feedback due to Doppler broadening of the structural ,
mater ia l resonances has been found to be of some importance relative
to the contribution of fissile mater ia l present in the reac tor . The p re
sent study aims at assess ing this effect quantitatively for typical fast
sys tems. Latest basic data pertaining to the description of the resonan
ces for all the important s t ructura l elements like F e , Cr, Mo etc. were
compiled and processed to generate the temperature and composition
dependent self shielded c ross sections using intermediate resonance
approximation to improve upon the existing Cadarache Cross Section
Library in which self shielding factors were conspicuously absent for
all these nuclides.
REFERENCE
1. M. L. Sharma and S. Ganesan, Proc. National Symposium on
Radiation Physics, Mysore University (1976).
1 • 8 The. Effect of 'Usii^-^Statistic_al; Unresolved Resonance Region on the ...Reliability of Calculated Dpppler Constant. as^ a...Function of Sodium Voiding in a Fas t Cri t ical Assembly (S. Ganesan-and M. M. Ramanadhan)
The calculations of'isotopic and groupwise break down of
Doppler constant,' made using IGDOP program , f o r ' Z P R - 6 - 7
assembly for the cases of no sodium voiding and full sodium voiding (2) • :
show that the region of importance in the calculation of Doppler constant shifts from the resolved to : the unresolved resonance region
- 8 -
for all the fissile and fertile isotopes present in the reac tor . Not only
the plant safety factor goes down in the case of sodium voiding but also
the magnitude of the calculated Doppler constant becomes less rel iable.
While the former effect is well known to be due to the spectra l harden
ing, the lat ter effect a r i s e s because of the s tat is t ical representat ion of
neutron induced cross-sec t ion data in the unresolved resonance region.
High resolution cross-sec t ion measurements for the fertile and fissile (3) isotopes as recommended by de Saussure and Perez a r e necessary to
alleviate this problem.
REFERENCES
1. S. Ganesan and M. M. Ramanadhan, "The Calculation of Isotopic
and Groupwise Breakdown of Doppler Constant for Fas t Systems",
RRC-FRG/RP-103 (1976).
2. S. Ganesan and M. M. Ramanadhan, "On the Reliability of Calcu
lated Doppler Constant as a Function of Sodium Voiding in
LMFBRS" (To be published).
3. G. de Saussure and R. B. Perez , Proceedings on Nuclear Cross
Sections and Techniques, Washington D . C . , U .S .A . , 3-7 March
(1975) (CONF-750303) 371 (1975)
•'•• 9 Study of the Relative Merits of Various Computational Models for Evaluating Resonance J(0>ft ) Function (P. Bhaskar Rao and S. Ganesan) •
Fas t and accurate evaluation of resonance J ( ^ ^ ) function
is of great importance in the calculation of the Doppler coefficient
of large fast power r eac to r s . In the past, a number of computational (2-7) models have been developed and reported in the l i te ra ture . The
degree of sophistication and computing t ime requirement var ies for (8) each model. We have evaluated the resonance J(6> ^ ) function
for & > 10 and b>lQ using the models of Steen , Sahni and
- 9 -
Menon , Nicholson and Grasseschi , Gelbard , Hwang , and that (7) used in the code DOPINTv ' . The relative mer i t s of the models with
regard to the accuracy and the computing t imes have also been .(8) compared
In Table 1.9.1 the computing time requirement , the average dis
crepancy and the maximum, discrepancy for each model over the range
of 0. 005 £&<£ 80, and 5 x 10" ^ -4. 80.0 are presented. It is seen
that Hwang's model is the most accurate but somewhat time consuming
while Steen's model is very efficient and fairly accurate . A suitable (9) combination of these two models were incorporated in the code DOPSEL
TABLE 1.9.1
Average and maximum Discrepancies in the Values of J Function and
Time Requirements for Computation
Quantity
Hwang's Model
Steen's Model
Nicholson's Model
Gelbard's Model
Sahni's Model
DO PINT Model
AD (%)
MD (%)
CTR (m sees)
0. 0
0. 0
9.4
0.4
3 .0
1.5 .,
0.1
0 .3
11.. 0 .
3 .0
40.0
1.9
0.05
5 .0
130. 0
0 .3
10. 0
46. 0
, AD = Average discrepancy
MD = Maximum discrepancy
CTR = Time requirement for computing the J function.
REFERENCES
1. L. Dresner , Resonance Absorption in Nuclear Reactors ,
Pergamon P r e s s , New York, 1960.
- 10 -
2. N. M. Steen, Nucl. Sci. & Engg. 38, 244. (1969).
3. S.V.G. Menon a n d D . C . Sahni, Atomkernenergie, 20, 265 (1975).
4. R. B. Nicholson and G. Grasseschi , "A Fast Accurate Technique .
for calculation of the Resonance J Function", ANL-7610 (1969).
5. E .M. Gelbard, Nucl. Sci. & Engg. 38, 249 (19^9).
6. R .N. Hwang, Nucl. Sci. & Engg. 52, 157 (1973).
7. R. Shankar Singh and G.A. Desai, "DOPINT - A Program to
Calculate Resonance Integrals and Multigroup Self Shielded Cross
Sections", BARC - RED/TPS/117 (1966).
8. P. Bhaskar Rao and S. Ganesan, Atomkernenergie 2 9, 255 (1977),
9. S. Ganesan et a l . , "DOPSEL, A Code for Evaluation of Self
Shielded Fac tors in Resolved and Unresolved Resonance Region",
RRC-6 (1975).
1.10 Improvements to Resonance Self-shielding Corrections in the Code EFFCROSS (M. L. Sharma)
A detailed study of heterogeneous resonance self shielding was
made. More accurate algorithms for computing collission probabilities for
accounting for heterogeneity and for computing Dancoff correct ion in modified
Sauer 's approximation as suggested by Bonalumi have been incorpo
rated in the code EFFCROSS . The modifications made were tested
for successful implementation and gave a difference of 150 pcm with
ear l ie r and new method for the sample problem of FBR-500 core.
Various interpolation schemes used in the generation of self-
shielding factors were studied with a view to select the best ones for
incorporation in the code .EFFCROSS. A code INTERPOL-has. been
written incorporating the ear l ier schemes used in the code EFFCROSS (2) and the latest schemes sugges ted 'by Kidman . Studies pertaining to
- 11 -
chese schemes have been reported in an internal note . Efforts a re
being made to incorporate the new schemes in the code EFFCROSS to
study the overall effect on the integral pa ramete r s .
REFERENCES
1. M. L. Sharma, "EFFCROSS-A Code for Generating Effective
Cross Sections from Cadarache Cross Section Library"'. RRC
Report under preparation, ii
2. R . B . Kidman, Cross Section Factor Interpolation Schemes,
HEDL-TME-71-40, Hanford Engineering Development Labora
tory (1971). ••
3. M.L. Sharma, R. Venkatesan and R. Shankar Singh, "Compara
tive Study of Different Interpolation Schemes for the Generation
of Self-shielding Fac to r s" , RRC-FRG/RP-121.
1.11 Static, Analysis of .FBTR. (S. "krishnan, T .M. John, S.M. Lee, C . P . Reddy, M. M. Ramanadhan and R. Shankar Singh)
To provide complete reac tor physics data for the detailed
design justification of FBTR, for the operation manuals and for the
safety r epo r t s , neutronic analysis of FBTR employing the exact data
from the recent drawings and specifications of FBTR was continued.
The FBTR total power and power per subassembly were
evaluated , using two-dimensional cylinder geometry and hexagonal
geometry diffusion codes. The calculated power distribution is in (2)
fair agreement with that measured in Rapsodie (Fortissimo) , It
"was found that the power variat ion between subassemblies located at
the same distance from the core centre is about 2% when all the
control rods a re out and about 4% when all the rods a re inser ted
uniformly. The insertion of control rods was found to sharply peak
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the radial distribution leading to a reduction of power by 15% in the i . , -.
peripheral row.
In order to evaluate the i rradiat ion damage and the thermal
design of certain FBTR s t ruc tura l components like the grid plate, neutron
and thermal shields and the reac tor vessel , the total flux, fast flux and (3) power generation in these components were calculated . The flux levels
(2) were found lower thani those calculated for Rapsodie (Fortissimo) due
to the presence of thoria blankets in FBTR as compared to the urania
blankets in Rapsodie.
Several alternate reflector and blanket configurations were
studied for FBTR. Replacement of the outermost1 row of nickel ref lec
tor subassemblies by thoria. subassemblies was found to lead to the
interest ing resul ts summarized in Table 1 .11 .1 . The reduction in the
thickness of nickel reflector resu l t s in the increase of cr i t ical mass 233
by two fuel subassemblies while the U production ra te increases by 235
26% and U destruction ra te increases only by about 1. 8%.
TABLE 1.11.1 FBTR Physics Paramete r s for a Thinner Ni Reflector
Paramete r
Number of fuel S/A
Number of Ni S/A
Number of ThO S/A
Total Fuel oxide (kg)
Uranium oxide (kg)
Initial breeding ratio 233
Initial U production \ (100% load factor) (kg/year)
235 Initial U destruction (100% load factor) (kg/year) Maximum flux/power (nv/MW)
8.305
Thinner Nominal
65
143
342
180.77
126.54
. 0.52
Reflector
67
93
390
186.33
130.47
0.64
10.536
12.292 12.515 b'. 769 x ' l ' 6 1 4 0. 758 x l b 1 4
- 13 -
The power generation in the nickel, thoria, s teel subassemblies
and fuel in storage positions was calculated. The t ransport of core gamma
rays was found to appreciably contribute to the total power in the f irs t
r o v of nickel reflector subassemblies. The power shift in the blanket
regions due to build up of fissile mater ia l was also ascertained.
The danger coefficients of different isotopes at different loca
tions in the reac tor , the subassembly worths, the reactivity variations
due to core boundary movements and design tolerance levels, and the
isothermal temperature coefficients have been also computed.
REFERENCES
1. S. Krishnan, T. M. John, S. M. Lee and R. Shankar Singh, "FBTR
Total Power and Power per Fuel Subassembly", RRC-FRG/
RP-100 (1976).
2. RAPSODIE - FORTISSIMO, Rapport de Surete, CEA-N-1387 (1970).
3. S. Krishnan, M. M. Ramanadhan, S.M. Lee and R. Shankar Singh,
"Flux Levels and Heat Generation Rates in Per iphera l Components
of FBTR", RRC-FRG/RP-112 (1976).
1.12 Gamma-ray Heating in F.BTR (R. Vaidyanathan, S. Krishnan, S.M. Lee and R. Shankar Singh)
A study of gamma-ray t ransport in FBTR has been taken up.
A knowledge of the gamma-ray heat deposition distribution in the
reac tor is essential for proper heat removal design. The assumption
that gamma-ray energy is locally deposited is found to underestimate
the heating in the reflector and shield regions and also in s tee l samples
placed in the core . A first estimate of the gamma ray flux distr ibu
tion was obtained using the code DTF-IV and the coupled n -o (3)
c ross-sec t ion l ibrary CASK . Since the CASK l ibrary is inappropriate
- 14 -
.> (4) for LMFBR applications a new n-% library^ has been subsequently procured and is being processed for further gamma transport studies.
REFERENCES
1. R. Vaidyanathan, S. Krishnan, S. M. Lee and R. Shankar Singh,
"Gamma-ray Heating in FBTRM, RRC-FRG/RP-105 (1976).
2. K. D. Lathrop, "DTF IV, A . F o r t r a n IV Program for Solving the
Multigroup Transport Equation with Anisotropic Scattering",
LA-3373 (1965).
3. "CASK, 40 Group Coupled Neutron and Gamma-ray Cross-sect ion
Data", RSIC Report DLC-23 (1974).
4 . W . E . Ford et a l . , "Coupled 100 n-21 ^ Cross-sect ion Library
for EPR Calculations", ORNL/TM-5249 (1976).
1.13 Effective Multiplication Factor , Control Rod Worths, and Neutron Flux due to Inherent Source in Subcritical L^jdj£g_of__FBTR (T.M. John, S.~M. Lee and R. Shankar Singh)
The feasibility of achieving the first and subsequent s t a r t
ups of FBTR without using an auxiliary neutron source is currently
under investigation . In continuation of studies reported ear l ie r
one dimensional, twenty five group, diffusion theory calculations (3)
were made for the effective multiplication factor, control rod
wor ths , and total and thermal equivalent fluxes in the core and in
the detector locations, in a se r i e s of subcrit ical loadings of FBTR.
The variation of the effective multiplication factor (K )
with fuel loading was established and initial cri t icali ty was found
to be achieved with a loading of 49 fuel subassemblies, when the
central subassembly location is vacant, the test s tee l subassemblies
a re replaced by fuel, and nickel reflector subassemblies a re used
in place of the nominal core outer fuel subassemblies for the sub-
cr i t ica l loadings.
- 15 -
The control rod worths increase as the number of fuel sub
assemblies loaded increase varying from 740 pcm for the 6 subassembly
loading to 2000 pcm for the full core .
The total flux at the cere centre varies with core loading
according to the relation,
f
5 where f=( l -K)/K is the negative reactivity and S = 2. 8 x 10 is the
(4) est imated number of neutrons emitted per second from a fresh
FBTR subassembly. The quantity C is a slowly varying function of
the fuel loading and control rod insertion, with a mean value of 0. 05.
The ratio: 'A' of the thermal equivalent flux at the detector
location to the core centre total flux is an important parameter for
determining the adequacy of the detectors used to monitor the s tar tup. ( * ) -c:
It is measured w ' to be 1 x 10 in RAPSODIE (Fort issimo). We
made calculations for both RAPSODIE and FBTR and found that the
reduction in detector flux due to the use of thoria blankets in FBTR
as compared to urania blankets in RAPSODIE is almost exactly
compensated for by the increase in detector flux due to the use of
graphite moderator in the FBTR detector block as compared to
concrete in RAPSODIE. Thus the same ratio may be expected to
be valid for FBTR.
Our calculations indicate a strong dependence of the
detector flux on the presence , of storage fuel subassemblies . One.
dimensional, homogenised cylinder geometry calculations showed
that the ratio1 . 'A'decreased by a factor grea ter than 2 when the
22 storage fuel subassemblies a re replaced by steel. The ratio;
v a s also found to have a weak dependence on the control rod
position,, tending to decrease as the control rods a re inserted.
- 16 -
The ra t io 'A' also var ies with the fuel loading. An
approximately l inear decrease of 'A' as the core loading is decreased
was found, the value falling by a factor of 5.4 for the 6 subassembly
loading as compared to the full core loading.
REFERENCES
1. D. B. Sangodkar and K. Pandurangan, "Neutron Source for
Startup of FBTR", RRC FBTR/FRG/66200/DN-06/R-0-1-2
(1976).
2. T. M. John, S. M. Lee and S. Krishnan, "Approximate
calculations for Neutron Flux due to Inherent Source in
Subcritical Loadings of FBTR", RRC-FRG/RP-79 (1975).
3. T .M.John, S.M. Lee and R. Shankar Singh, "Effective
Multiplication Fac tor , Control Rod Worths and Neutron
Flux due to Inherent Source in Subcritical Loadings of
FBTR", RRC-FRG/RP-117 (1977).
4. * K . P . N . Murthy and R. Shankar Singh, "The Alpha,
Gamma and Neutron Emission Character is t ics of the;
' F r e s h Fuel of FBTR", RRC-FRG/RP-75 (1975),
5. RAPSODIE-Fortissimo Rapport de Surete, CEA-N-1387
(1970).
1.14 FBR-500 Neutronics Studies (T. M. John, S.M. Lee and R. Shankar. Singh) .
Several design calculations were performed for the
5 00 MWe oxide fuelled LMFBR (FBR-500) being studied at (1 2)
RRC ' . The calculations were performed using the one
- 17 -
(3 4) dimensional diffusion theory code MUDE ' with the 25 group (5) Cadarache Cross-sect ion Set
i) Fuel Subassembly worth at core centre and under water
Safety studies were made to find the variation of the
reactivity worth of a fuel subassembly with the number of fuel pins
in the subassembly. The worths were calculated at the core centre
and under water s torage. It was found that the worth at the core
centre of a higher enrichment outer core fuel subasssembly varied
from 35 0 pcm to 520 pcm as the number of fuel pins in the subassem
bly was var ied from 169 to 271. The corresponding variat ion in
central worth for the lower enrichment inner core fuel subassembly
was from 185 pcm to 275 pcm. The effective delayed neutron fraction
of the system was calculated to be 380 pcm. The worths of the sub
assembl ies under water storage were in all cases found to be well
below unity.
ii) Equilibrium Core Composition
Burn up calculations were performed to obtain the equili
br ium core composition based on an initial fuel reload cycle scheme.
The refuelling interval was taken as 300 days and the discharge
burnup as 50000 MWD/Te. The reactivity loss from the beginning -
of-cycle (BOC) of the fresh core to the BOC of the equilibrium
core was calculated to be 1800 pcm. The reactivity loss from
BOC to end-of-cycle (EOC) for the equilibrium core calculated to
be 2800 pcm. It was found that the initial plutonium composition
of Pu-239/240/241/242 = . 6879/. 2460/ . 0526/. 0135 changed to the
values . 6816/. 2580/. 0458/. 0145 for the inner zone and . 6744/. 2620/
. 0488/. 0148 for the outer zone' in the equilibrium core.
- 1 8 -
iii) Design of control rod system
Pr i l iminary • calculations have been made for the optimisa
tion of the number and distribution of the control elements in FBR-
500. Since an exact representat ion of 'off-centre control rods is not
possible with the one dimensional code MUDE so the method of La-(7)
capelle was used to derive the worth of such rods using the
exactly calculable worth of a centrally located control rod and the
danger coefficient distribution of the control rod mater ia ls in the
reactor . This method does not give the shadow effect of the rods
which were est imated separately by cylindrical model approximate
calculations.
Fo r the first iteration suitable values were assumed
for the sodium and steel fractions in the control subassemblies
which were also assumed to be of the same size as the fuel
subassemblies . The worth of a natural boron rod was found to
be about 86% of that of a 30% enriched boron rod and about 66%
of that of a 90% enriched boron rod- For the prel iminary design
it was assumed that natural boron is used; a study of boron is
destruction ra t e s and control rod life t imes would be made la ter
to see whether use of enriched boron has to be considered.
. Based on the calculated values of burnup reactivity loss
and effective delayed neutron fraction for this system a total r e
activity worth of 10,000 pcm was fixed for the control system to
allow for burnup, power and temperature feedback coefficients,
shutdown margin and operating margin.
A very strong shadow effect was found to^ occur which
greatly reduced the worth of the rods when inser ted simultaneously
Some of the resu l t s for a single bank of rods a re given in Table
1 .14 .1 . These resu l t s indicate that the number of rods required
-19-
for the desired antireactivity is too large to be accommodated in one
ring. Fur ther» it was found difficult to adjust for power
profile stability with just a single bank of rods . Hence two banks
of rods "were considered.
TABLE 1.14.1
Row Number of
Bank
2
3
4
5
6
7
Shadow
Worth of a single
Rod (pcm)
770
733
682
606
476
330
Effect for Single
Required Number of
Rods (Fi rs t Iterate)
13
14
15
17
21
31
Bank of Control
Average of a Rod Inserted
worth When in
Bank (pcm)
185
304
485
527
238
83
Rods
Required Number of Rods (Second
Iterate)
54
33
21
19
42
121
The required reactivity control was assumed to be equally divided
between the two banks. The mutual shadowing effect in this case
is indicated, in Table 1.14.2 which gives the average worth of a
control rod when both banks a r e inserted as well as the average of
the worths of the control rods when singly inserted. It is seen that
the maximum average worth occurs when hexagonal rows 3 and 6 a re
chosen for the location of the two banks. The suitability of these
locations from the point of view of power profile stability and interac
tion of the control rod movements with the power dist.< ibution and the
burnup is being studied.
- 2 0 -
TABLE 1.14.2
Shadow Effect for Two Banks of Control Rods
Average Worth Average Worth Row Row of a Rod When of a Rod When
Number of Number of Singly both Banks are Inner Bank Other Bank Inserted (pcm) Inserted (pcm)
2
3
4
2
3
4
5
2
3
4
5
5
5
5
6
6
6
6
7
7
7
7
671
658
639
569
560
547
524
430
425
418
405
661
683
657
736
795
610
384
431
510
414
265
Accurate calculation of control rod worths in two and-
three dimensions with t ransport correct ions a r e being made in order
to a r r ive at the prec ise number of control elements required.
iv) Thorium utilisation
Calculations were made for the effect of using thorium
radial blankets in place of uranium blankets' in FBR-500. Assuming
the relat ive worths of the fissile nuclides produced to be identical,
very smal l reduction in the breeding ra t io was found to occur. The
internal breeding ratio.' 1 plus axial uranium blanket breeding ra t io ' .
was found to be about unity even when thorium radial blankets a re .,
used thus indicating the possibility of having a self sustaining uranium-
plutonium cycle with production of excess U-233 from the thorium
blankets.
-21-
REFERENCES
1. T .M. John, S. Krishnan, d.M. Lee and R. Shankar Singh,
"Pre l iminary Design of a 500 MWe Fas t Breeder Reactor",
RRC Activity Report 1974, RRC-8 (1975).
2. T . M . John, S. M. Lee and R. Shankar Singh, "Pre l iminary
Physics Design of a 500 MWe Fas t Breeder Reactor" ,RRC
Activity Report 1975, RRC-19 (1976).
3 . T . M . John, "MUDBrA One-dimensional Diffusion Theory
Neutronics Code" , RRC-FRG/RP»60 (1975).
4. C. Bore , Y. Dandeu, C. Saint-Amand, "Resolution de 1'
Equation Multigroupe de la Diffusion dans Une Geometrie a
Une Dimension et Calcules Annexes: Code MUDE"CEA.-R-
2923 (1965).
5. J .Y. B a r r e , M. Heindler, T. Lacapelle and J. Ravier ,
"Lessons Drawn from Integral Experiments on a set of
Multigroup Cross Sections", Paper l - 1 5 , P r o c . Int. Conf.
on the Physics of Fas t Reactor Operation and Design, London
(1969)
6. T . M . John, S. M. Lee and R. Shankar Singh, "Reactivity
Worths of FBR-500 Fuel Subassemblies at the Core Centre
and Under Water Storage for Various Numbers of Pins per
Sub assembly" , RRC-FBR/500/01/09 (1976).
7. T. Lacapelle , "Point Sur les Etudes de B a r r e s de Controle
de Phenix •• 250H - Etudes P re l imina i res d'Implantation",
CEA-DRP/SETR 66/251 (1968).
- 2 2 -
1.15 An Ana lys i s of the B r e e d i n g iCapabi l i ty of V a r i o u s F a s t j l e a c t d r
F u e l s
( C . P . R e d d y , S. M. L e e and R. Shankar Singh)
A s tudy of the b r e e d i n g capabi l i ty of a wide r ange
of fas t r e a c t o r fuels b a s e d on r e c e n t eva lua t ions of neu t ron c r o s s
s e c t i o n s has been m a d e , V a r i o u s combina t ions of the f i s s i l e 233 238
m a t e r i a l s Pu and U and the f e r t i l e m a t e r i a l s U and Th, in
the f o r m of m e t a l , oxide, c a r b i d e and n i t r i d e , w e r e c o n s i d e r e d .
A s p h e r i c a l r e a c t o r of cons tan t vo lume (3000 1) and compos i t i on
( F u e l / S t e e l / S o d i u m =• 0, 3 5 / , 1 5 / , 50) was chosen ignor ing d i f fe rences
in the t h e r m a l and bu rnup c h a r a c t e r i s t i c s of the v a r i o u s fuels . The
c lad f ract ion was kept low and the fuel dens i ty high (100% t h e o r e
t i ca l ) in o r d e r to obtain the uppe r l i m i t s of the b r e e d i n g c a p a b i l i t e s .
50 c m thick b lanke t s with the s a m e f e r t i l e m a t e r i a l of the s a m e
c h e m i c a l type as p r e s e n t in the c o r e , followed by 15 c m s t e e l r e
f l ec to r have been p r e s u m e d .
The r e s u l t s p r e s e n t e d in Table 1 .15 ,1 show that the
b r e e d i n g gain i n c r e a s e s f rom oxide th rough c a r b i d e to m e t a l fuel
for a l l the f i s s i l e - f e r t i l e c o m b i n a t i o n s . The i n c r e a s e is l a r g e for 2 38 233
the P 'u-U s y s t e m , m o d e r a t e for the h y b r i d P u - T h and U 2 38 ' 9 33
U s y s t e m s and 'qu i te s m a l l for the. tj - T h s y s t e m . N a t u r a l n i t r i d e 15
i s found in f e r io r to c a r b i d e whi le e n r i c h m e n t in N makes the n i t r i d e only a l i t t l e s u p e r i o r to the c a r b i d e .
233 The U -Th combina t ion c o m p a r e s v e r y poor ly with
2 38 the o ther combina t ions and in fact the P u - U and hybr id oxide
233 s y s t e m s a l l have b r e e d i n g ga ins g r e a t e r than the U - T h m e t a l
9 33 9 38
s y s t e m . Hybr id c y c l e s employ ing P u - T h and U -U f i s s i l e -
f e r t i l e combina t ions or m i x t u r e s of t h e s e a p p e a r v e r y p r o m i s i n g .
- 23 -
T A B L E 1 . 1 5 . 1
F u e l Type
Meta l
Oxide
C a r b i d e
N i t r i de
N i t r i de e n r i c h e d
m N
Breed ing C h a r a c t e r i s t i c :
F i s s i l e - F e r t i l e Combinat ion
P u - U 2 3 8
P u - T h ^ 3 3 ^ 3 8
U 2 3 3 - T h
P u - U 2 3 8
P u - T h 233 238
U 2 3 3 - T h
P u - U 2 3 8
P u - T h ..2 33 . .238
u233-™
P u - U 2 3 8
P u - T h 233 238
u233-™
P u - U 2 3 8
P u - T h u 2 3 3 _ u 2 3 8
U 2 3 3 - T h
s of F a s t R e a c t o r F u e l s
Inpi le . F i s s i l e Mass (kg)
1321
1511
1100
1341
1094
1392
820
1114
1217
1491
942
1231
1268
1575
1008
1341
1177
1400
929
1260
In te rna l Breed ing Rat io
. 1 . 4 4 0
1.02 2
1.186
0 .781
0. 939
0 .912
0 .875
0 .787
1 .100
0. 960
1 .003
0. 800
1 .043
0 .934
0.926
0 .761
1.127
0. 995
1 .013
0 .818
Breed ing Rat io
2 .020
1.630
1.699
1.301
1.442
1.380
1.374
1.226
1.598
1.462
1.483
1.260
1.512
1.401
1. 370
1.182
1.639
1.496
1.501
1.272
- 24 -
The reduction in breeding when the clad-fraction and
the reac tor excess reactivity a re increased, and the fuel smear den
sity is reduced, to values acceptable in current design practice was 0 3 o
estimated for the Pu-U oxide fuelled case. A large fall in breed
ing gain from ,442 to ,217 was found to occur due to these changes.
REFERENCE
1. C, P. Reddy, S .M.Lee and R. Shankar Singh, "An Analysis of
the Breeding Capability of Various Fast Reactor Fue l s " ,
RRC-16 (1977).
1,16 Analysis of Delayed Neutron Yield Data
(S. Krishnan, M. L. Sharma and S, M, Lee)
It has been repor ted in many laborator ies that a
discrepancy of around 2 0% exists between the measured and cal
culated centra l reactivity worths of the major fissile and fertile
nuclides in fast crit ical assembl ies . This is partly attributed to
the uncertainit ies in the delayed neutron data.
(2) In the past, the delayed neutron data of Keepin
have been employed in the central worth calculations. Recently,
based upon fresh measurements new delayed neutron yield evalua
tions have been proposed by Tomlinson- ', Cox and Tuttle
Calculations of the central worths of several nuc- -(6) lides in selected cr i t ical assemblies was undertaken using the
different delayed neutron yield data to study their effect on the
calculated/experimental (C/E) discrepancy. It was found that the
later evaluations lead to a higher value of effective delayed neutron
fraction and hence the central worth C/E ratio gets reduced by
about 7%.
- 25 -
Keepin's evaluations indicate that the: absolute delayed
neutron yield (a) increases with neutron energy approximately at the
same ra te as the total neutron yield ("}>) so that the delayed neu
tron fraction ( p "= ***/y ) is approximately independent of energy.
On the other hand the later evaluations show that a is approximately
constant (upto 4 MeV) so that p decreases with energy. The effect
of using constant Q> or constant a .was also studied for Keepings data
and showed that the latter assumption gives a better agreement com
pared to the former.
The resul ts of the central worths calculations for 235
U using the different data a r e given in Table 1 .16 .1 .
REFERENCES
1. R. Avery, Proc National Tropical Mtg. New Developments in
Reactor Physics and Shielding, CONF-720901, USAEC (1972).
2. G.R.Keepin, Physics of Nuclear Kinetics (Addison Wesley,
Reading, Mass. 1969).
3. L. Tomlinson, "Delayed Neutrons from Fission: A Compila
tion and Evaluation of Experimental Data", AERE-R-6993,
(1972).
4. S.A. Cox, "Delayed Neutron Data - Review and Evaluation"
ANL/NDM-5, (1974).
5. R . J . Tuttle, Nucl. Sci. & Engg. 56, 37 (1975).
6. S. Krishnan, M. L. Sharma and S. M. Lee, "Analysis of
Selected Fas t Crit ical Experiments Using Recent Delayed
Neutron Yield Evaluations", To be published in Atomkern-
energie.
- 26 -
T A B L E 1 .16 .1 235
C o m p a r i s o n of C e n t r a l W o r t h s of U jwith Different
- • Yield Data and Spec t r a
A s s e m b l y
E x p e r i m e n t a l va lue (Inh/kg)
C a l c u l a t e d / E x p e r i m e n t a l Ra t io Keep in Constant
Keep in Constant
T a m l i n -son a Cons tant
Cox a Cons tant
Tut t l e a Constant
SNEAK-7-A 757
ZPR-3-54 567
ZPR-3-53 530
ZPR-3-50 464
ZPR-3-49 282
ZPR-3-48 334
ZPR-3-56B 295
ZPR-6-6A 42
1.168
1 .380
1.282
1.139
1 .158
1.239
1.079
1.196
1.119
1. 301
1.216
1.086'
1.110
1.147
1. 026
1.136
1.084
1.273
1.184
1.052
1.072
1.147
0. 997
1.106
1.062
1.258
.1 .164
1. 031
• 1.049
1.122
0. 978
1. 085
1. 058
1.243
1.156
1. 028
1.046
1.119
0. 973
1. 080
1.17 Max imum Ay a i lableMe^chanic al Work in a C o r e Dis rup t ive Accident (P. B h a s k a r Rao and R. Shankar Singh)
The m a x i m u m avai lab le m e c h a n i c a l work has> been : obtained for
c o r e - d i s r u p t i v e acc iden t s in i t ia ted by v a r i o u s r e a c t i v i t y i n se r t i on r a t e s in - • ' • • ( I ) • ••; - • • • ; • • • • • p - - . •• . • . r
F B T R . Th i s i s r e q u i r e d in o r d e r t o p r ed i c t the m e c h a n i c a l effects of a
co re d i s rup t ive acc ident on the s t r u c t u r e s of the con ta inment . Ca lcu la t ions
have been p e r f o r m e d us ing two a p p r o a c h e s . The . f i r s t a p p r o a c h u s e s (2)
R a n d i e s ' e m p i r i c a l f o rmu la . The second approach u s e s f o r m u l a e
for the i s o t r o p i c - e x p a n s i o n ' o f a pe r fec t g a s ' a n d p r e d i c t s the expans ion
w o r k done by the f r e l v a p o u r a t ' h i g h p r e s s u r e s -expanding ' to a t m o s -
p h e r i c p r e s s u r e i se r i t rop ica l ly . The d i s c r e p a n c y - i n - t h e r e s u l t s obta ined
by the two a p p r o a c h e s i s found to be due to the a s s u m p t i o n of a p e r
fect gas behav iour of the fuel vapou r , the unce r t a in ty in the r a t i o c / c
- 27 -
and the empiricism of the relations used in the first approach.
REFERENCES
1. P. Bhaskar Rao, R. Shankar Singh and Ompal Singh, "Analysis of
HCDA in FBTR", RRC-FRG/RP-109, (1976).
2. J. Randies, Proc . IAEA Symp. Fas t Reactor Physics, Karlsruhe
1967, Vol.11, IAEA, Vienna (1968).
1.18 A code to Solve Neutron Transport Equation in Slabs-APARNA III (R. Vaidyanathan)
(4) APARNA III solves the t ransport equation in infinite slabs
To economise the shield calculations, where large thicknesses are in
volved, we have evolved a coarse-mesh algorithm. This is achieved
by building in greater details of the variation of collision source with
in a spatial segment. They a re obtained in t e rms of the 'finite 'moments,
with which we reconstruct the source shape. The moments a re defined
as X.I+,
"CO
The source shape can be evaluated in t e rms of N undetermined cons
tants . The program is res t r i c ted to forms linear in the constants.
This i s done by represent ing the unknown function in t e r m s of a good
'guess ' function, which is corrected by a polynomial expansion
S3 j<. is the guess function, which is represented by the sofar un
determined expansion. Pa rame te r s C a re evaluated preserving N moments defined by (1).
- 28 -
In addition to this feature, simple representat ions of the
source are permitted. These a re the l inear and exponential forms,
preserving gross features of the actual distribution. Gopinath et a l
have first worked out these forms in the ASFIT code. Our formula-
tion ' ' differs from that, by the fact that character is t ics of in
ternal variation of the source a re included. The dividends have been (2 3)
found to be excellent ' .
The code has been extended to multiplying media. Since
the evaluation of integral__flux parameters naturally enter our formu
lation, APARNA-III can furnish an accurate estimate of cri t icali ty
in reac tors (e.g. axial representation of cylindrical reac tors) and
flux disadvantage factors in the fuel cells of test facilit ies. Study
of t ranspor t of 0 - r a y s through iron is underway, for compari
son of the resul ts with DTF IV.
Extending the scope of the codes to curved geometries
has been undertaken.
REFERENCES
1. D. V. Gopinath, K. Santhanam and D. P. Burte, Nucl. Sci. &
Engg.52, 494 (1973).
2. R. Vaidyanathan, Atonikernenergie -29, 3:01 (1977). T'
3. R. Vaidyanathan, MA Coarse-mesh Algorithm to' Solve ""Neutron"
Transport Equation in Thick Shields", "Fifth 'International Conf.
on Reactor. Shielding, ORNL, Oak Ridge (1977).
4. R. Vaidyanathan, 'APARNA-III, An Extended Moments Algorithm
to Solve Nev-ron Transport Equation', RRC-FRG/RP- l3 l ( l977) .
5. R. Vaidyanathan, 'APARNA-II, Program to Solve Integral T r a n s
port Equation in Slab Geometry' , RRC-FRG/RP-123 (1977).
- 29 -
1.19 Random Sampling of Neutron Elas t ic Scattering Angle in Monte Carlo Transport Calculations. (K. P . N. Murthy, M. M. Ramanadhan and R. Indira)
In the Monte Carlo simulation of neutron t ranspor t , the random
sampling of elastic scat tering angle poses problems because the sca t t e r
ing is usually anisotropic and the degree of anisotropy is dependent on the
incident neutron energy. We studied a procedure based on the equi-proba-
bility table method . In this procedure the probability density function
(pdf) of the scat ter ing angle is given by
In Eq. (1), 4-MC^//V /d-^U i s the differential scat ter ing c ross section,
N(E) is the total scat ter ing cross section for the incident neutron of energy
E and jJU the cosine of the scat ter ing angle. We divide the range of LL
into N intervals such that.
Data on the differential scat ter ing c ross section are readily available. The (2)
KEDAKLibrary , for example, gives scat ter ing c ross section per unit
s teradian at twenty one equally spaced LL points. Using these data and
performing the integration-> in Eq. (2), we can determine / M E . ) ,
i = 2, 3 . . . . N and j = 1 , 2 . . . M. Here M is the number of energy points
at which the differential scat ter ing data are available. We then express
the energy dependence of jt*.* by a polynomial in x (x=E/7. 5-1),
given by, rf\,
jL}CX) * % *-\K ^ - - - (V K>1
- 30 -
The expansion coefficients &~ll<. a re determined under least square
fit cr i ter ion. Thus we reduce the bulk'of the differential c ross section
data into a set of N x n coefficients. The sampling of AC is done as
follows. For an incident neutron of energy F,, using Eq„ (3), we deter
mine fi.^ , i = 2 , 3 . . . N.. Two random numbers ^4 and %^_ a re
selected. , , lL . is given by
Using this procedure e las t id scattering events in sodium were s imu-(3) lated . KEDAK data was used. Sixteen equiprobable groups and foui
t e r m s in the expansion were used. Sample resul ts a re given in ref, 3.
The sampling procedure described is suitable for incorpora
tion in non-multigroup Monte Carlo Transport Codes. We see that in
this procedure, the interpolation of differential cross section over
energy variable is inherent.
REFERENCES ,
1. H. Kschwendt and H. Rief, "TIMOC - A General Purpose Monte
Carlo Code-for Stationary and Time Dependent Neutron Transport" ,
• E U R - 4519e (1970); • ' • • • '
2. I. Langer, J. J. Schmidt and D. Wolf, "Tables of Evaluated Neutron
Cross Sections for Fas t Reactor Mater ia ls" , KFK-750 (1968).
.3. K..P. N. Murthy, M. M. Ramanathan, R. Indira.and R. Shankar Singh,
"Random. Sampling of Neutron Elastic Scattering Angle in Monte
Carlo Transport Calculations", National Symposium on Radiation
Physics, . Mysore University, .(1976).
- 31
1.20 Track Length Biassing in Monte Carlo Simulation of Radiation Transport in Thick Shields (K. P . N . Murthy)
Problems involving radiation t ransport through thick shields
are character ised by large variance. Hence, for Monte Carlo s imu
lation, these require a large number of h is tor ies . This consumes
prohibitively large computer t ime. In fact it is practically impossible
to simulate some of the deep penetration problems by analogue Monte
Carlo .
Track length stretching is one of the usual variance reduction
procedures employed to overcome this difficulty. This procedure con
s i s t s essentially of sampling the inter collision optical distance x, of
the part icle from the probability density function (pdf),
UX) dx •=. A. **f(- **0 d^ --• CD
instead of the normal pdf,
Everytime we choose a x = x^ from eq. (1), the s tat is t ical weight of
the neutron is multiplied by a factor f l , given by
Levitt has studied the problem of particle t ranspor t through
one dimensional thick slabs using t rack length stretching technique.
Levitt kept 'a ' independent of particle direction. Ponti and Nagarajan
introduced a linear dependence of ' a ' on the cosine of the angle the (4)
part icle makes with important direction. We have studied linear
and exponential form for the direction dependence and have recommended
(see Table 1.20.1) optimum biassing parameters for low, medium and
TABLE 1.20.1
Comparison of Efficiencies of the Two Biassing Functions
' a = 1 a = exp ( -b ) Efficiency1*
(normalised)
0.5
Range of b for which Relative. Statistical E r ro r is within ±15%*=
0. 7 - 0. 9 0.7 0.8 0.9
0.242 0.702 0.593
Range of b for which Relative Statistical E r r o r is within±l5%f
1.3 2 :1 1.5 1.7 2.0
Efficiency" (normalised)
0.998
0.7' 0. 6 - 0. 8 0.6 0.7 0.8
0.195 0.219 0.181
1.0 1.5 0. 9 1.0 1.1
0.150 0.230 0.216
0.9 0.2 0 .7
0 .0 0.3 0.4 0.5
1.00 6.06 6.62 6.39
0.3 1.0
0. 0 0.7 0. 8 0.9
1.00 8.41
10.18 6.03
CO
The resul ts of 10, 000 histories have been used.
^The resul ts of 1, 600 histories have been used.
- 33 -
high scattering slabs of thickness 20 mfp. In Table 1 .20 .1 , P is the
scattering probability and £• is the efficiency index defined as the
inverse of the product of the variance and computer t ime taken per
his tory. We find that the Massing scheme described could improve the
efficiency of the. Monte Carlo by as much as a factor of ten. Of the
two biassing functions we find that the .exponential; form for the
direction dependence performs; better*.
REFERENCES
1. Leo B.Levitt , Nucl. Sci. & Engg. 31, 500 (1968).
2. C. Ponti, "Angular and Track Length Distribution Biassing
in Monte Carlo Deep Penetration Studies". ORNL-RSIC-29
(1971) p. 27.
3. P. S. Nagarajan, P. Sethulakshmi and C. P. Raghavendran,
BARC /I-134 (1975).
4. K . P . N . Murthy, "Direction Dependent Exponential Biassing in
Monte Carlo Simulation of Radiation Transport in Thick Shields",
Fifth International Conference on Reactor Shielding, ORNL,
Oak Ridge (1977).
1.21 Albedo - Monte Carlo Technique for Radiation Streaming through Ducted Shields .
, , (K .P .N . Murthy and R. Indira)
Simulation of radiation s treaming through ducted shields can
be effectively achieved by adopting albedo concept. This procedure
assumes the particle to be reflected at the point of incidence on the
duct wall, with reflection probabilities .defined by total and differential
albedos. These albedo data are determined by experiments or theore
t ical models.
- 34 -
TABLE 1.21.1
Comparison of Experimental Results with our Simulation
(Russian.iRoulettei. Played at 0. 3 Weight) (8100 Histories)
Dis tance in feet
2
3
4
5
6
8
10
12
15
20
25
30
34
37
40
T h e r m a l n-f lux ( e x p e r i men ta l )
2 .52
1. 84
1.13
7 .50 ( - l ) a
5, 22 (-1)
2 . 7 0 (-1)
1.52 (-1)
8 .70 (-2)
4 . 1 0 (-2)
1.33 (-2)
„ 5 .40 (-3)
2 .34 (-3)
1.23 (-3)
8 .20 (-4)
5 .50 (-4)
T h e r m a l n-f lux (ca lcu la ted)
2. 64
1.68
1. 09
7 .51 (
5 .33 (
2 .79 (
1.55 (
9.48 (
4 . 5 1
1.-32
6. 08 <
2 .22
1.01
9. 02
5 .19
-1)
-1)
-1)
-1)
-2)
-2)
-2)
-3)
[-3)
' -3 )
(-4)
(-4)
Re la t ive S t a t i s t i c a l E r r o r in ca l cu la t ions
(%)
0 .28
0.44
0 .67
0 .88 •
1.11
1.62
2 .20
2 .84
4 . 2 5
6 .11
10 .06
11 .30
9 .87
2 .44
1.31
Deviat ion f rom E x p e r i m e n t
(%>
4. 76
8. 70
3. 54
0 .13
2 . 1 1
3 .33
1. 97
8. 97
10. 00
7.52
1 2 . 5 9
5. 13
17. 89
lo.'oo 5.64
a R e a d as 7. 5 x 10
- 35 -
We have developed a computer program DUST* ' to simu
late neutron scattering through rectangular multi legged (right angle
bends) ducts. Using DUST we have simulated the experiments of (2)
Maerker and Muckenthaler on thermal neutron s t reaming through
straight square concrete ducts. The total and differential albedo data
for thermal neutrons reflection at concrete surface used in DUST are
the ones recommended in Ref. 3.
Table 1.21.1 compares our computations with the measure
ments . • The maximum deviation is found to be 17. 9%. The relat ive
Statistical e r r o r was kept within 15%.
REFERENCES'
1. K . P . N . Murthy, R. Indira and R, Shankar Singh, "Simulation
of Neutron Streaming through Ducts in Shields", R R O F R G /
RP-122 (1977).
2. R . E . Maerker and F . J . Muckenthaler, Nucl. Sci & Engg. 29.
444 (1967).
3. R . E . Maerker and F . J . Muckenthaler, Nucl. Sci & Engg. 26_.
339 (1966).
1.22 Response Matrix Construction for Unfolding Gamma Spectra (R. Indira, A. K. Jena and K. P. N. Murthy)
To unfold the gamma spectrum from the pulse height
spectrum measured with NaI(Tl) detectors , it is necessary to cons
truct the response of the detector system as a function of gamma
energy. One of the methods is to measure the gamma spectra of
some reference, monoenergetic gamma, sources and using, interpola
tion schemes between the responses at these part icular energies , the
response function is constructed.
- 36 -
A method has been proposed where the response of the
detector to a monoenergetic gamma, is divided into four or five regions
and each region is represented by an analytical function. The analytical
functions a re gaussian, modified gaussian and quadratic polynoraials. The
constant coefficients in the analytical function are expressed as a func
tion of energy for all the regions. Using these ,the response functions
a re constructed.
To determine these constants, as a function of energy, the
gamma spect ra of the monoenergetic reference gamma sources are
measured with the detector. The different regions are fitted using non
linear least square fitting methods, to the recommended analytical func
tion, taking care that the function of one region joins smoothly with the
function of the adjacent region at the boundaries. The constants so
obtained are now fitted as a function of energy. This method has been
found to be successful in unfolding the gamma spectra , to a very good
extent .
A program 'BLOOM' has been developed employing this
method, for response matrix construction.
REFERENCES
1. Toshiaki Sekine, Sumiko Baba and Hiroshi Baba, "Analytical
Functions Representing Response Functions of Nal (Tl)
Detector System to Gamma Rays", ORNL-Tr-2 941 (1971).
2. H. Baba and T. Sekine, J. Tlad'ioanalC. Chem. J2j). 109 (1976).
1.23 Effect .of. Gamma-ray. Transport .on the Prediction- of Central Pin Clad Temperature in a Spent Fuel Subassembly (P. Bhaskar Rao, N. V . L . S. Sarma, R. Shankar Singh and B. S. Sodhi)
- 37 -
A heat- t ransfer model to predict the tempera ture d i s t r i
bution in a spent fuel sub-assembly has been developed based on the
processes of conduction and radiation. This model has been further
(2)
improved to include the energy t ranspor t to the sheath by the gamma-
rays leaking from the pins which escape absorption by other pins. The
improved model predicted that as much as 20% of energy emitted as f>
and % - rays escapes out of the fuel sub-assembly into the coolant
without actually heating the fuel pins. The remaining part only contr i
butes to heat the pins and maintain the temperature distribution. The centra l pin clad tempera ture , required to evaluate the cooling ra te
o
requirement , has been found to be less by 30 C than what was predic
ted by the ear l ie r model, which was 650 C for a typical case .
REFERENCES
1. N . V . L . S . Sarma and P. Bhaskar Rao, RRC Report to be published.
2. P . Bhaskar Sao, N . V . L . S . Sarma, R. Shankar Singh and B.S.Sodhi,
"Effect of Gamma. Ray Transpor t on the Prediction of the Central
Pin Clad Temperature in a Spent Fas t Reactor Fue l Subassembly",
National Symposium on Radiation Physics, Mysore University(l976).
- 3 8 -
2.':. R E A C T O R DESIGN '' '.,.••
2-1 Choice of Coolant" Entry, Sleeves for FBTR. • , (Amitava Sur, M. . Rajan,' A. S. Dixit and S„ B. Bhoje)
The FBTR fuel, blanket and reflector subassemblies are.
supported by the grid plate in their respective support sleeves.. Coolant
entry sleeves are fitted at the. bottom of these support sleeves. Sodium
enters through.these entry sleeves and flows through the subassemblies
via the support.sleeves. These sleeves are not part of the Rapsodie,-
Fortissimo i design; but .were added in the-FBTR design as .an additional
safety measure'. >.•:>•;'•
Choice of a particular type was made among various types
of entry sleeves having axial or semi-radial entry and provided.-with,
multiple holes of different diameters and shapes. The aspects consi
dered for the'selection were: safety, hydraulic characteristics/ "strength
and 'fabricational. simplicity. From safety point of view it .was tp.be
ensured that any object that may pass through the hole in the entry"
sleeve would, cause only a partial blockage of the subassembly flow
passage. The hydraulic characteristics considered were, pressure drop
in the sleeve and the possibility of cavitation. These were studied using
the hydraulic test loop that is available at REL, RRC
Based on the results of the hydraulic experiments and
considering other aspects mentioned above, two types of sleeves were
chosen for the FBTR. Type A sleeve, having 12 holes of 12 mm
diameter each, was chosen "for the fuel subassemblies and the .nickel
reflector subassemblies of flow zone No. V. Type B, having 16 holes
of 4 mm diameter each, was chosen for the rest. Both these types
provide semi-radial entry.
-39-
REFERENCE
1. Amitava Sur, M. Rajan, A. S. Dixit and S. B. Bhoje, "Hydraulic
Testing of Entry Sleeves", RRC-FBTR/FRG/31173-DN-01 (1976).
2- 2 gtudy^of^Leakage,.Incidents and i ts Effects in,.FBTR_. (K.K. Vaze and A.S. Dixit)
To facilitate the review of core safety, the provisions for
cooling the core under normal, upset and emergency conditions of the
reactor were compiled. The leakage incidents were categorised into
three types for analysis:
a) Leakage outside Al-'cell, which houses reactor vessel
b) Leakage inside Al -ce l l but only in reactor vessel , its
double envelope remaining leaktight
c) Leakage inside Al -ce l l , both in reactor vessel and
its double envelope
In the: first type the safety of the core is assured by
emergency nitrogen cooling circuit upto a leakage rate of 40 l i t r e s /
sec.
In the second type it was found that sodium is retained in
the reactor vesse l at sufficiently high level to sustain forced circulation.
In the third type, forced circulation is possible only for a
short duration at the start depending upon the leak ra te and emergency
cooling is not possible. So this incident is the most severe of all the
three types. It was found that heat could be transferred to the biolo
gical shield cooling circuit only if a layer of sodium of a certain height
is available above the subassembly heads. In order to maintain the
level of sodium at this required level, a flooding circuit has been
included which dumps 65 m of sodium at 150 C into the reactor
vessel . The amount of sodium to be dumped has been reduced
- 40 -
by the provision of the safety vessel surrounding the re rc tor
vessel and the inlet pipe. Since it was decided that a minimum of 5
minutes might be required to initiate flooding action, a leak rate of
only 30 m / n r COuld be taken care of by such a provision. For the
calculation of temperature of sodium, under this incident, the following
model was employed. Upto 2 hours, which is the time required for
complete flooding, it is assumed that only 60 kw of heat rate is removed
from the vessel by the biological shield cooling circuit and afterwards
the removal increases to 300 kw because of enhanced temperature of
safety vessel wall due to sodium filling the gap between safety vesse l
and reactor vessel . The heo.t capacity of the core and the nickel
reflector alone was taken into account for temperature calculation. It
was found out using the computer code 'HEATING' and by hand calcula
tion that the sodium temperature reaches a maximum of 722 C as per
the above model and this is well below the boiling point of sodium
•which is about 900 C.
REFERENCE
1. A.S. Dixit, S. Govindarajan, K. K. Vaze and S. B. Bhoje, Core
Cooling During Normal Operating Conditions and Emergency",
RRC-FBTR/FRG/31000-DN 01 (1976).
2. 3 BOW-A Computer Program for Subassembly..Bowing.Calculations for Fast Reactor Cores (Bir Singh)
Bowing analysis of fast reactor core is a complex problem
which needs a deep understanding of core support concepts, optimum
number and positions of spacer pads and knowledge of subassembly
interaction behaviour under bowing of various assemblies due to diffe
rential thermal, swelling and creep s t ra ins . As a first step towards
this objective, computer code 'BOW has been written which performs
bowing calculations for a single subassembly fixed at its bottom and
restrained from bowing laterally at the level of pads.
- 4 1 -
Individual contribution of thermal expansion, void swelling and
irradiation induced creep bowing, restraining loads and bending s t r e s
ses are calculated in the code by employing separate suborograms.
The complete history of subassembly bowing could be obtained by
using the code, which performs the analysis in a ser ies of progres-
sive time steps. Swelling and creep behaviour of mater ial "is supplied
in mathematical form as separate subprograms so that refinement in
the data could be easily adapted.
The present code could be utilised to study the behaviour of
complete core by suitable modifications.
REFERENCE
1. Bir Singh and S. B. Bhoje,"BOW - A Computer Program for Sub
assembly Bowing Calculations for Fast Reactor Cores",
RRC-FRG/FBR-500/31/76 (1976).
2- 4 Sensitivity Analysis of, Fiiel Geometry and Operating Conditions for FBR-500 (Bir Singh, S. Govindarajan, S. B. Bhoje, T. M. John, S. M. Lee and R. Shankar Singh)
Fuel geometry and operating conditions significantly affect the
reactor performance parameters like doubling time, fuel cycle cost
and Pu inventory. The parameters pertaining to fuel geometry consi
dered for the present study are clad thickness and active core height.
Those pertaining to operating conditions a re maximum linear heating
of fuel, coolant pressure drop allowed through the core and the maxi
mum temperature r i se through core. The analysis was done using
the computer codes HYDRO(1% MUDE *2 ' and COST*3 . The resul ts
are discussed below.
- 4 2 -
The clad thickness was found to have a large influence on
doubling time and fuel cycle cost. In the range of thicknesses studied
viz. 0.5 mm - 0. 9 mm, it is found that doubling time is increased
by about 10 years as the thickness increases and fuel cycle cost is
increased by about 10%. Pu inventory is not much affected.
Increase in the allowable pressure drop from 40 - 90 m of
sodium at 500 C reduces doubling time by about 5 years . Both fuel
cycle cost and Pu inventory decrease but not significantly.
Active core height has large influence on fuel cycle cost since
number of pins to be fabricated every year is inversely proportional
to active core height. Effect of active height on other parameters
is not very significant.
It is generally observed that increase in linear power and
maximum temperature r i s e through core a re desirable for better per
formance of the reactor .
REFERENCES
1. Bir Singh, S. Govindarajan and S. B. Bhoje, "HYDRO-A Computer
Program for Thermohydraulic Design", RRC-FRG/FBR-500/31/76
(1976).
2. T.M. John, "MUDE - One Dimensional Diffusion Theory Neutro-
nic Code", RRC-FRG/01100/RP-60 (1975).
3. Bir Singh and S. B. Bhoje, "COST - A Computer Program for
Fuel Cycle Study", RRC-FRG-/FB2-500
- 4 3 -
2 .5 . Studies for Optimisation of Subassembly Size for FBR-500 (Bir Singh, S. Govindarajan and S.B. Bhoje)
For a given pin diameter, the size of a subassembly depends
on the number of pins it c a r r i e s . The size of the subassembly af
fects the neutronic, mechanical, handling and economic charac ter i s
t ics of the reactor . .- In the present study, the parameters that
influence the choice of the subassembly size were .identified and a
tentative quantitative evaluation was made
Increasing the subassembly size improves economy. It was
found that the reduction in reactor-down-time due to s ize- increase
from 169 pins per subassembly to 271 pins, could result in an
additional revenue of about 11 crores of rupees per year . Design
complications due to increased subassembly size ar ise in the form (2)
of increased bowing. Computer program 'BOW was used to evaluate the design implications. The resul ts indicate that the problems are not insurmountable. Thermal performance of the core is not much affected by sub-assembly size.
F rom the point of view of handling, the important parame
te r s are subassembly weight, res t ra in t loads at contact pads and
the decay heat rate per subassembly. Subassembly weights for the
three cases namely 169 pins per subassembly, 217 pins and 271
pins were found to be 260 kg, 332 kg and 415 kg respectively.
Restraint loads were calculated using the code 'BOW for a single
res t ra in t and these were 387 kg, 635 kg and 988 kg respectively.
Corresponding decay heat ra tes were 6.3 kW, 8 kW and 10 kW
after 80 days of cooling.
-44-
REFERENCES
1. Bir Singh, S. Govindarajan and S. B. Bhoje, "Prel iminary Studies
for Optimisation of Subassembly Size for FBR-500", RRC-FRG/
FBR-500/31/76 (1976).
2. Bir Singh and S. B. Bhoje, "BOW - A Computer Program for
Subassembly Bowing Calculations for Fas t Reactor Cores",
RRC-FRG/FBR-500/31/76 (1976).
- 4 5 -
3. REACTOR ENGINEERING
3. 1 500 kW Sodium Loop (R. D. Kale, R. Prabhakar, R.Selvaraj , K. Balachander, K. Swaminathan and M. Rajan)
500 kW sodium loop is being erected in REL to gain experi
ence in the erection and operation of large sodium systems. The
loop consists of a centrifugal sodium pump, a heat source with elec
t r ica l hea ters , an intermediate heat exchanger, an air cooled te rmi
nal heat sink, on line purification system and the necessary cover
gas, electr ical power and instrumentation systems
During 1976, piping and erection of major components have
been completed. Piping consists of about 80 m of 3£" Sch 5 and 2M
and l" Sch 40 pipes. All welding was carr ied out by tungsten inert
gas welding with back purging with argon gas to produce sound un-
contaminated welds. Welded joints were radiographed and helium
leak tested to a sensitivity of 10 std. em /Sec. Hundred electrical
U heaters were welded to heater flange to complete the heater
assembly. The sodium to air heat-exchanger, sodium pump and the
surge tank were erected in position.
Electrical and instrumentation works are nearing completion.
REFERENCE
l ."500 kW Loop!'Activity Report 1975, RRC-19 (1977) pp.54-55.
- 4 6 -
3. 2 Experimental Study of Sodium Deposit Build-up on Rotating Plugs (R. Prahhakar;, R.Ramani and R. D. Kale)
In Fas t Breeder Test Reactor, rotating plugs act as top clo
sure ensuring radiation and thermal shielding and isolation of radio
active cover gas from outside. . Nominal clearances are maintained
between the plugs and reactor vesse l permitting rotation of plugs
during refuelling operations. These enclosed clearances face high
temperature sodium pool, as a resul t of which sodium deposits tend
to build up on the cooler surfaces enclosing the clearances. This
eventuality leads to seizure of mating par ts , impeding fuelling opera
tions. An experimental set up has been installed to study the so
dium deposits build up between reactor vessel and large rotating
plug and to investigate the effectiveness of different preventive
methods.
The set up consists of a scaled down mock up of the r e a c
tor vesse l and large rotating plug. To simulate the natural con
vection pattern expected in the reactor , Grashof, Prandtl and Nus-
selt numbers are maintained at the values expected in the reac tor .
The gap width, temperatures at various points, temperature gra- .
dients, cover gas medium and pressure are maintained at the
values expected in the reactor . The large rotating plug diameter
is scaled down by a factor of four in the model. The sodium hold
up is about 400 kg.
Four runs each of 500 hr duration after attaining steady
state conditions have been completed. The first two runs were
without any preventive measure . For the third run an anticon-
vection baffle was installed between the reactor vessel and the
plug (Fig. 3. 2. 1). In the fourth run, a labyrinth type restr ic t ion
-47-
xc
LARGE ROTATING PLUG.
REACTOR VESSEL
MAIN SODIUM VESSEL.
BAFFLE (INSTALLED IN RUNS 2AND3^
LABYRINTH (INSTALLED IN RUN i. )
' > ' • ' '
16mm
230 A
16mrr
32mrE_
ANTl CONVECTION BAFFLE (INSTALLED IN RUNS 3 AND A)
1\LEVEL PROBE ARM.
vrv
4
'
o o
0 674 V6L2
\
ei
16
ANTICONVECTION BAFFLE
REACtORVfrSSEL. LARGE ROTATING PLUG.
S L S A \ \ . \ - S .
16
«S673 o
/ / /
-3 HOLES »10 120 APART PCP.SJ2. .
LABYRINTH .0 400
FIG.3.2.1.. SODIUM VAPOR DEPOSITION EXPERIMENT.
- 4 8 -
was fitted in addition to the anticonvection baffle. The baffle and
labyrinth were installed to impede the natural convection in the
clearances. The impurity level in sodium at the end of first
three runs was kept below 80 ppm oxygen. It was within 160
ppm. oxygen at the end of fourth run. The sodium temperature was
maintained at 550 + 15 C.
The following conclusions are reached on completing four
runs:
1) Without any preventive measure, sodium deposits build
up in cooler zones (Fig. 3 .2.2) .
2) Anticonvection baffle does not seem to be very effective.
3) Result with labyrinth restr ic t ion is encouraging and an
appreciable reduction in deposit has resulted.
4) The deposits in the cooler zones were found to be local
crystalline growths and these contained more than 90%
sodium.
- 4 9 -
FIG.3.2.2 SODIUM DEPOSITS ON LARGE ROTATING PLUG MOCK UP
-50-
3 • 3 Delta Ferrite Measurement by Magnetic Saturation Method (R. Prabhakar)
Most austenitic stainless steel weld metals are produced to
deposit small amounts of delta ferrite in the weld to prevent cra
cking and microfissuring. At elevated temperatures like 550 C,
presence of delta ferrite causes sigma phase formation resulting
in loss of impact strength and corrosion resistance. Taking into
consideration the above, the welding specifications for Fast Bree
der Test Reactor stipulate ferrite requirement in the range of
2.5 to 5.5%. For high temperature operation, overall delta fer
rite content of the weld metal is of importance and a set up based
on measurement by magnetic saturation method has been developed
to measure this.
Magnetic saturation method is based on the following prin
ciple. The intensity of magnetisation at saturation of a sample of
a given composition is proportional to the quantity of magnetic
phase (delta ferrite in this case) present. In this set up the in
tensity of magnetisation at saturation of an all weld specimen is
measured and by using empirical relationships, the delta ferrite
content is estimated. The set up consists of an air core solenoid 5
capable of producing 2 x 10 A. turns/m. flux coils and a sensi-(1) tive ballistic galvanometer .
Measurements have been carried out on a large number
of specimens using this set up. Readings are found to agree
quite closely with those reported by a French Laboratory which
uses a similar set up. An error analysis has indicated that the
results are accurate to + 1% ferrite or better upto 5% ferrite.
- 5 1 -
The set up is now being used for ferr i te measurements
necessary for qualifying welding procedure as well as for t e s t
ing weld coupons for fabrication of components of FBTR.
REFERENCE
1. R. Prabhakar and R. D. Kale, "Measurement of Delta F e r r i t e
by Magnetic Saturation Method", P roc . Seminar on Welding
for Specialised Applications and Safety in Welding, Indian
Institute of Welding, Madras Branch, 1976, pp. B1-B8.
3,4 Spdiurn Ionization Detector (K. Swaminathan)
The sodium ionization detector (SID) currently under
development (Fig. 3.4.1) is a sensitive sodium-to-gas leak de
tector for use in liquid metal cooled Fas t Breeder Reactor .
The detector re l ies on the relat ive ease with which sodium or
sodium-containing compounds may be thermally ionized, com
pared with other possible constituents in a c a r r i e r gas (nitro
gen, oxygen, water vapour, etc. ) . The surface of a heated
filament is utilised for preferentially forming Na ions from the
elemental sodium or i ts compound in the gas. These ions a re
then collected on an adjacent collector electrode which is main
tained at a negative potential relat ive to the filament and this
-current is electronically recorded. In the absence of sodium or
i ts aerosol near the filament, the SID produces only a smal l
background signal .
Many designs of SID of different s ines, mater ia ls and
electrode configuration were t r ied out at REL before obtaining
the current model to achieve a low background current . A back-
AMMETER
SODIUM IONISATION DETECTOR. VAC. GAUGE.
THE DETECTOR&ITS ELECTRONICS.
VENT. REG
r-TU
DETECTOR
HEATER \
i
c c c
u S j p==U
\
D
D 2_
I =£3=
ROTAMETER
LINE HEATER-XMICRO FILTER.
I — 7
J
VAC. PUMP.
83 OIL TRAP <
N2C/UNDER SODIUM\
FIG. 3.4.1. EXPERIMENTAL SET-UP.
^
-53 -
ground cu r r en t of less than 0.5nA at a collector voltage of 2 00V (3) is attainable in nitrogen gas after ageing a new filament for
a few days. Several tes ts were car r ied out to check the response
of the detector to detect sodium vapour in a standard (commercial
purity) nitrogen c a r r i e r gas and in a special nitrogen gas of low
impurity content in oxygen, water vapour etc. SID response to
sodium oxide and hydroxide aerosols ar is ing out of a sodium fire
was also noted. This has indicated that SID can be used to detect
leaks in operating sodium loops. Design and experiments a re
under way to a s sess the maximum sensitivity of the detector, to
prolong the operating life of the filament used and to a s sess its
performance in radiation environment.
REFERENCES
1. John Roboz, Introduction to Mass Spectrometry, (Wiley Inter-
science, New York 1968) pp. 127-128.
2. P. G. Wilson a n d G . R . Brewer, Ion Beams with Appl icat ions
to Ion Implantation, (John Wiley and Sons, New York 1972)
pp.74-75.
3. S.Datz &F.H.Taylor , J. Chem. Phys. 25, 389 (1956).
3. 5 Hydraulic Test Rig (AmitavaSur and M. Rajan)
In the core of the Fas t Breeder Test Reactor, sub -
assembl ies a re provided with f low-restr ict ing devices to ensure
proper distribution of coolant. The sizing of these devices must
be finally done by experimental verification. Usually testing of
these flow r e s t r i c t o r s in a water loop is sufficient and resu l t s
of the tes ts can be applied to actual conditions of sodium cool
ant by similitude technique. Different s izes of flow r e s t r i c to r s
- 5 4 -
were tested in a water loop, for flow and pressure drop charac
te r i s t i cs and cavitation point. These character is t ic curves were
converted to corresponding sodium values by similitude techniques.
The sizes of res t r ic t ions were selected based on the flow required
in the subassemblies for removing the heat generated without any
r i sk of cavitation.
Orifice plates with four holes will be provided in three
different zones of FBTR fuel subassemblies. Orifice plates of dif
ferent dimensions were tested in the water loop in the temperature
range of 30 to 80 C. Sizes of orifice plates were tentatively deci
ded.
Capillary tubes will be provided in blanket and reflector
zones of FBTR sub-assembl ies . Testing of capillary tubes of
different internal diameter and length is being car r ied out in the
water loop.
3. 6 Steam Cleaning of Senium Contaminated Components (M. Rajan)
The components removed from a sodium system must be
cleaned before r euse . The residual sodium can be reacted with dif
ferent agents like alcohol, steam, water, mist etc. depending on
the nature and size of the part to be cleaned. Cleaning of sodium
components can be hazardous and demands careful planning. Com
ponent cleaning by steam is advantageous in many cases due to
smooth and non-violent reaction between sodium and steam. Com
ponent cleaning by steam was therefore, experimented at the REL.
The main vesse l , wherein the components a re kept for cleaning is
made of 250 mm. dia. MS pipe and is approximately 650 mm in
height. Saturated s team is available from an oil fired boiler of
-55-
capacity 100 kg/hr at a p ressure of 14 kg/cm . The preheating is
car r ied out by circulating steam, in a jacket around the vesse l . The
preheating prevents condensation of s team in the main vesse l , thus
precluding any sodium-liquid water reaction. The components to be
cleaned were kept inside the reaction vessel and steam was admitted.
The hydrogen liberated during the cleaning process gets diluted in the
steam and escapes at the top. The sodium hydroxide formed during
the reaction is drained off from the bottom. Components like wire
mesh f i l ters , pipe bends etc. were cleaned successfully, To have
a bet ter control over the excessive temperature r i s e due to reaction,
in cer tain cases , a mixture of inert gas and s team will be attempted
in future.
3. 7 Dummy Fuel Pin Test Rig (R. Selvaraj a n d C . S . Narayanan)
The fuel pins of the Fas t Breeder Test Reactor must with
stand high temperature sodium environment satisfactorily during their
residence in the reac tor . A high temperature (600 C) sodium r ig has
therefore been constructed td ca r ry out endurance testing of a dummy
fuel pin c luster . It is intended to evaluate part icularly the performance
of end plug welding and spacer wire attachment. The dummy fuel pins
will be subjected to a sodium velocity of 4 m / s e c . at 600 C which
represen t s a slightly more severe condition than that expected in the
reac tor . The r ig consists of an electromagnetic pump (capacity
2 m /hr ) , a heater pot, a test section and a storage tank (Fig. 3.7.1).
To maintain the purity of sodium in the r ig , two diffusion cold t r aps
have been prpvided. In addition a plugging indicator is provided to
monitor impurity concentration by measuring the plugging tempera ture .
The r ig was commissioned in October 1976 and some ini
tial runs were made to purify the sodium in circulation. The diffusion
type cold t raps were effective in removing impurit ies related to low
saturation tempera ture . The plugging indicator detected the presence
- 56
GAS'LINE
EXPANSION POT.
HEATER VESSEL
iiIN£ PLUGGING INDICATOR.
MAIN FLOW "-METER. <H +
1
AIR
\ *.
2 O h-u tu CO
V h-
i —
CO Ul I—
1 CO CO
o z Q.
< co _l_
FIG. 3.7.1. .DUMMY FUEL PIN TEST RIG.
- 57 -
of multiple impurit ies in the sodium. The dummy fuel pins will be
subjected to endurance tes t as soon as these a r e made available.
3. 8 Liquid Metal Seal Experiment T R . D , Kale and M. Rajan)
This experiment was s tar ted with a view to acquiring expe
rience in constructing large seals for the Fas t Breeder Test Reactor
The first aim was to achieve a helium-tight sea l that consists of an
eutectic alloy of tin and bismuth (Sn 42% Bi 58%) maintained in a
stainless s tee l tub. The bond (adherence) between the eutectic and
stainless container i s the most important thing to obtain the desired
helium-leak tight seal . It i s known a t the same time that such binary
alloys cannot be readily bonded to a s tainless s teel part . A surface
treatment procedure was therefore evolved which would prepare the
surface suitable for obtaining good bond with the eutectic alloy. This
consisted of pickling in a mixture of HNO„ and HF followed by cleaning
with' ethyl acetate and demineral ised water . A suitable flux was used
during the application of eutectic alloy to the surface. The eutectic
alloy was applied by means of a specially made hot iron maintained at o
about 350 C. Inspite of the appropriate surface t reatment .it
needed considerable skill to coat the stainless s teel surface
successfully using the eutectic alloy. Several t r ia l pieces were coated
with the eutectic alloy. The bond was tested mechanically in all cases
and metallurgically in some. With the procedure thus finalised, the
stainless s tee l tub of the liquid metal seal mock up was coated
with the eutectic alloy. This was followed by pouring of the alloy into
the stainless s tee l tub from a storage tank at a tempera ture of 25 0 C
(Fig. 3 .8 .1) . The seal alloy was allowed to solidify by natural
cooling. Bubble leak test was car r ied out under a gas p res su re of
0.3 kg / cm and no leak was detected. The sea l was subjected to a
thermal cycling between 200 C and room tempera ture for 12 t imes .
After every cycle a bubble leak test was car r ied out which gave
58 -
COVER GAS.
ALLOY CERRO BEND (Sn.Bi.Pjt-.cd alloy)
INNER TUB
OUTER TUB SIZE:. 1000X150X400mm
ALLOY CERROTRU (Sn.Bi ,a l loy)
LIQUID METAL,SEAL (TIN BISMUTH EUTECTIC.)
N REACTOR VESSET"
• ROTATING PLUG.
'.'!'-.
FIG. 3.8.1. L.M.SEAL EXPERIMENTAL SET-UP.
- 59 -
satisfactory r e su l t s . At the end of the 12th the rmal cycling, a helium -7
mass spectrometr ic test was conducted with a sensitivity of 5 x 10 3
s t d p m / s e c . No leak was detected. Fur ther thermal cycling tes ts
and ageing t es t s at temperature a re planned. The performance of
the seal appears to be encouraging.
REFERENCE
1. R .D . Kale and M. Rajan," Liquid Metal Seal Experiment?,' in
Activity Report 1975, RRC-19 (1977) pp. 47-48.
3. 9 Potential Prop Sensors for Sodium Loops (R. Selvaraj)
During loop charging and dumping operations, it is a great
convenience to the operator to know the presence or absence of
sodium in a particular pipe section. The monitoring of charging or
successful dumping operation is thus facilitated especially in the case
of large sodium sys tems. The detection of plugged fi l ters or fill
line sections is very rapid and much before any indication from level
detectors in components can be had. The detection of the presence
or the absence of sodium in a pipe section is readily accomplished
by use of a device called Potential Drop Sensor (P. D. Sensor)which
makes vise of the excellent e lect r ica l conductivity of the liquid metal
compared to iithat of normal s t ruc tura l mater ia l s . In principle, this
sensor detects the change in the potential drop across a certain length
of sodium piping for a constant current fed to the pipe section. As
sodium r i s e s in the pipe section it lowers -..the total res is tance of the
circuit by shunting the s tainless s teel pipe. This resu l t s in a lower
potential drop. The reverse is t rue during draining of sodium from
a pipe section. A set of copper wires i s used to pass the current
and another set of wi res brazed to the pipe serves to measure the
- 6 0 -
potential drop with the help of a mill ivoltmeter. These sensors were
used in the sodium purification' loop. An improved version of this
device has been now developed which uses a reed switch and a
current feeding t ransformer . With the improved version a lamp
indication can be had on a control panel to indicate sodium or no
sodium in a pipe section. Many such P . D . sensors have been instal
led in the 5 00 kw sodium loop and a re undergoing final tes ts .
- 6 1 -
4. DESIGN OF SODIUM CIRCUITS
4 ,1 Anti-deflooding System for FBTR P r i m a r y Sodium Pumps (T .R. Ellappan and R. Chandramohan)
Sodium flow from reactor vesse l to intermediate heat ex
changer to pump is by gravity in FBTR.. Sodium level in the pump
decreases in proportion to the square of the flow r a t e . Beyond a 3
pump flow r a t e of 400 m /hra the pump gets deflooded. An anti-deflooding system is incorporated in p r imary pumps to operate them
3 safely upto 650 m / h r . This system functions well if the sodium
flow ra tes from both the pumps a r e same or the difference in flow
r a t e is low. But if the flow difference exceeds a permiss ible l imit ,
de-flooding of the pump operating at a higher flow ra te or flooding
of the pump operating at a lower flow ra te occurs . An investiga
tion was made to pre-determine the safe permiss ible operating
zone when one pump operates at a different flow ra te than the
other.
Figure 4 . 1 . 1 explains the principle of operation of anti-
defloooding sys tem. The upper par t and suction chamber of the
pump a re separated by an anti-vortex plate . A by-pass circuit
takes sodium from pump delivery to upper par t . A valve controls
the by-pass flow. The sodium level stabilizes in the upper par t
when leak towards suction chamber (q ) is equal to the total flow to
wards upper par t constituted by hydrostatic bearing sodium flow and
the by-pass flow through control valve (q + q' ). Figure 4 . 1 . 2
gives the schematic of p r imary sodium main "circuit.
Sodium level change in the pump is a function of flows
Q. and Q , p re s su re drop coefficients K . , K0 and K and the ra t io
of the p res su re drop coefficients k i / f o (Fig. 4 . 1 . 2 ) . Calcula
tions indicated that to prevent flooding as well as deflooding of the
- 62 -
AR6QN,NOZZIE
• • • • • • ' " • a :
SUCTION
]J
t
MFCHAN1CAL SEALS. :
SKIRT '
SHAFt
CASIN6
CONTROL VALVE
ANTI-VDRTFX PLATE
LEAK-TIGHT SEGMENT
HYDROSTATIC BEARING
.BY- PASS
.SUCTION CHAMBER
DELIVERY
FIGURE..: L.U
SKETCH SHOWING THE PRINCIPLE OF OPERATION OF
"•• .'•'.-' :- PUMP ANTI - DEFLOODING SYSTEM
REACTOR
LOOP 2 Ki
02
Q1+Q2 K2
D
LOOP 1 Ki
Qi
PUMP
w
K - PRESSURE DROP
. COEFFICIENT [Ap=KQ 2 )
LEVEL IN REACTOR VESSEL..CONSTANT
LEVEL IN IHX. AND PUMP -VARIABLE
FIGURE-4.1.2 •
SCHEMATIC OF PRIMARY MAIN CIRCUIT
- 64 -
pumps, the factor Ri / k. should be between 0.0418 and 0.0173. It
was found that a value of k i / k = 0.03 provides large safety margin
against flooding and de-flooding incidents when the pumps operate at
different speeds. Figure 4 . 1 , 3 shows the permissible operating zone
situated between flooding and de-flooding l imits for hi/k. = 0 .03,
If the difference between the two pr imary pump flows is
determined for all the points located on the curves encircling the
permiss ib le operation zone., it can be concluded that the maximum 3
safe permiss ib le flow difference is 175 m /h r . If the difference 3
exceeds 175 m / h r , reac tor will be tripped and pumps will be slowed
down to 500 rpm to remove decay heat.
With one pump alone operating, the maximum permiss ib le 3
flow r a t e was found to be 576 m /h r to prevent de-flooding incident
for k i / k = 0 .03 .
It is' foreseen that , if the leak-tightness between the anti-
vortex plate and leak tight segment is very good., we may have to
dri l l holes in the anti-vortex plate to achieve the factor fc»i/R. = 0 .03 .
Evidently this has to take into account the p res su re drop charac ter
istics of the by-pass control valve.
REFERENCE
1. T . R . Ellappan and R. Chandramohan, Study of Sodium Levels
;c P r i m a r y Pumps During Operation at Different F low- ra t e s ,
RRC-FBTR/FRG/32120/DN-2 (1976),
4 . 2 An Evaluation of Design P r e s s u r e for the F . B . T . R . Secondary Sodium Heat Transfer System and its Components in case of a Leak in Steam Generator (A.K. Rajput)
- 65 -
I
200 300 400 500 600 700 800
•FLOW IN PUMP-1 m3/hr
FIGURE-4.1.3
LIMITING FLOW OF ONE PUMP AS A FUNCTION CF
FLOW OF THE OTHER PUMP FOR Jli k
0-03
- 66 -
In a fast reac tor plant, choice of liquid sodium as a heat
t ransfer -medium is justified because of its excellent heat t ransfer
proper t ies and high boiling point at low pressure (850 C at 1 a tm).
High t empera tu re s , required for bet ter plant efficiency, a r e t he re
fore, attainable without the need of a pressur ised sys tem. However,
the system and its equipments have to be designed to withstand ex
cess t ransient p ressu re result ing from sodium/water react ion in the
s team genera tor , due to any eventual leak of water into sodium
The present study aims at analysing the thermo-hydraulic
phenomenon of sodium-water or sodium-steam, react ion, and conse
quent build up of p ressures in sodium at various points of the sys
tem. This is necessary to check the design of various equipments
in the sys tem for these conditions
Thermo-hydraulic equations describing p r e s s u r e , tempe
r a t u r e , adiabatic growth ra te of hydrogen bubble (formed as a r e
sult of sodium-water reaction) a re solved simultaneously with equa
tions governing the leak ra te of s team or water. A Runge Kutta (1,2)
method of fifth order has been used * . Subsequent to a leak (3)
in superheater portion, leak ra t e of s team is found by ''Fannoflow analysis 'of s team flowing in the ruptured tube. On the other hand,
leak ra te of water , in case of rupture in evaporator portion, is (2)
analysed by an inertia controlled model . Pressure / f low t rans ien t s ,
in the r e s t of heat t ransfer loop and its components, a r e evaluated
by the simultaneous solution of quasi-hyperbolic par t ia l differential
equations of momentum and continuity balance. Solution is (4)
effected by the 'Method of charac te r i s t i cs '
A computer p rogram in FORTRAN-IV- for obtaining r e
sults for the hydrogen bubble p r e s s u r e and tempera ture etc. , water-
s team leak r a t e s and p re s su re s at various circuit locations as
functions of t ime has been developed.
- 67 -
REFERENCES
1. B. Schwab, "Report on Sodium-water Reaction in Steam Generator
of Phenix, Report No. DRP/EMTR/SR222 (1970).
2. A.K. Ra jpu t , "Pressure Transients Resulting from Sodium-water
Reaction in the Steam Generator of F . B . T . R . " , RRC-FBTR/FRG/
33411/DN/20 (1977).
3. A.H. Shapiro, The Dynamics and Thermo-dynamics of Compress i
ble Fluid Flow, (Ronald P r e s s Company, New York 1953).
4. V .L . S t ree te r , Fluid Mechanics (McGraw Hill Book Company
1962).
- 6 8 -
5. RFACTOR FUEL HANDLING
5.1 Analytical and Computational Methods for Predict ing Temperatu re Distribution in a Fas t React.or Spent Fuel Pin Bundle (N.V.L . S. Sarma, B .S . Sodhi and P„ Bhaskar Rao)
An analytical method for predicting clad tempera ture
of the pins in a fast reac tor spent fuel pin bundle has been developed.
This method takes into account the three important energy t ransfer
(2)
processes viz. gamma ray , conductive and radiative heat energy-
transport between the various pins and the hexagonal sheath of the
bundlej, to solve the energy balance equations. Based on this ana-
lytical model, a computer algorithm ', TICOFUSA, coded on IBM
370/155 in FORTRAN IV has been developed to solve the energy
balance equations. The model has been generalised so that it can
be applied to a fuel sub-assembly consisting of any number of pins.
Besides clad temperature of the p ins , the code prints
out the energy values for each pin for various energy t ransfer p ro
c e s s e s . An i terative approach has been introduced into the code
to enable rapid convergence to the cor rec t tempera ture distribution
from a suitable guess . The code has the options to take into
account any combination of the energy t ransfer p roces ses , depend
ing on the contribution of the individual p rocess to the total energy
t ranspor t . The model can be extended to cases where the sub
assembly is in sodium environment instead of gas . This model has
been utilised in the heat - t ransfer calculations performed to predict
the cooling medium requirements for the Irradiated Subassembly
Storage Facil i ty of Fas t Breeder Tes t Reactor at Kalpakkam, India.
The resu l t s obtained a re shown in Table 5 . 1 . 1 .
REFERENCES
1. N.V. L .S . Sa rma , P . Bhaskar Rao and B .S . Sodhi, "A Method
for Predict ing Tempera ture Distribution in a Fas t Reactor
Spent Fuel Bundle! RRC-21.
- 6 9 -
TABLE 5 .1 .1
Fract ional Energy Transpor t by Various P r o c e s s e s and the
Tempera ture Distribution in the Spent Fuel Pin Bundle
Cooling ra t e 30 gm/sec of a i r
Energy T r a n s - Energy T r a n s - Energy port by port by t ranspor t by •$ rays radiation Conduction
W/m W / m W / m
1
2 .
3
4
5
6
7
8
9
2ATH
647
640
626
619
595
580
552
547
529
430
3.42
3.53
3.74
3.85
4.23
4.49
5.06
5.16
5.58
17.6
17.4
17.1
16.9
16.4
16.3
8.6
9 .0
5 .9
2 .4
2 .4
2 .6
2 .7
2 . 8
2 .7
12.1
11.7
14.4
Cooling ra t e 10 gm/sec of a i r
1-1
2
3
4
5
6
7
8
9
EATH
683
677
664
657
636
623
599
594
579
500
3.42
3.53
3.74
3.85
4.23
4.49
5.06
5.16
5.58
17.8
17.6
17.3
17.1
16.7
16.6
8.6
9 .0
5 .8
2 .2
2 . 3
2 .4
2 . 4
2 .5
2 .3
10.3
9 .9
12.2
S.No. of the
pin
Temp. pin/ clad °C
of
- 70 -
2. P . Bhaskar Rao, N.V. L. S. Sarma and R. Shankar Singh,"Effect
of Gamma-Ray Transport on the Prediction of Central Pin Clad
Tempera ture in a Spent Pas t Reactor Fuel Subassembly',' National
Symposium on Radiation Phys ics , Mysore University, Mysore
(1976).
- 71 -
6. ELECTRICAL AND INSTRUMENTATION ENGINEERING FOR. FBTR
6. 1 Neutron Detectors and Instrument Channels for FBTR (D.B„ Sangodkar, C. Paramas ivam Pil lai and N . C . Rathod*)
Development of compensated ion chambers and associated
instrument channels for FBTR has been reported ear l ie r . In con-
tinuation of this development p rog ramme, evaluation of boron coated
counters , fast pulse channels and analogue reactivity meter was ca
r r ied out.
Boron coated counters for delayed neutron detection in
FBTR a r e specified for operation with fast pulse channels operating
in c u r r e n t - m o d e . This operation obviates the need for preamplif iers
(2)
close to the counters . Evaluation of the counter performance in
cludes determination of plateau cha rac te r i s t i c s , sensitivity, neutron
flux range and life tes t . Tes t s of plateau charac ter is t ics and deter
mination of sensitivity were done using the standard neutron source
in Electronics Division, Bhabha Atomic Research Centre . Tes t s of
neutron flux range were car r ied out in Zerl ina reac to r . Plateau
charac te r i s t ics and l inearity to neutron flux as obtained during the
tes ts a r e shown in Figs- 6 . 1 . 1 , a, b and c. Plateau length of 100
volts with a slope of 0.3% per volt was obtained. Thermal neutron sensitivity of the counter is more than 4 cps /nv. Its neutron flux
4 range is upto 5 x 10 nv . The dimensions of the counter a r e :
Dia. 34 mm and length 450 mm. Life tes t on the counter is in
p r o g r e s s .
Fas t pulse channels in conjunction with high-sensitivity
fission chambers a r e intended for neutron monitoring in the s ta r t -up
range of FBTR. These channels operating in current mode need no
* Electronics Division, Bhabha Atomic Research Centre
- 72 -
a
< or. *-z o o
1000 -
800
600 -
400 -
200 -
T T
SLOPE
0 - 2 4 % / V
0-27 ° / o / v
0 • 46 °/o/ V
+ 600V 4 700 V +800 V
OPERATING VOLTAGE
FIG. 6.1.1.a. BORON COATED COUNTER-PLATEAU CHARACTERISTICS
en a
i— < a: z
o o.
1000
800 -
600
4 0 0 -
2 0 0 -
- l — — i 1 r
-1-2 -1-4 -1-6 -1 -8
D ISC B I A S S E T T I N G IN VOLTS
FIG. 6.1.1.6. DISC BIAS Vs COUNTRATE
- 73 -
(/» 7 X 1 0 -o. u UJ
< v. z z» o o
IO'H
10 H
DETECTOR - F f S I O N CHAMBER
CABLE - M JLTISHIELOEO COAXIAL
10 10 10
APSARA REACTOR POWER IN Watts
FIG. 6.1.2. START UP CHANNEL COUNTRATE LINEARITY MEASUREMENT
v> a. t j
tu
< cc z o o
INSTRUMENT.-DND CHANNEL
CABLE. -MULTISHIELDEO COAXIAL
lOmw 100mw 1w
ZERLINA REACTOR PCWER IN mw
FIG.6.1K. BORON C0ATE0 COUNTER COUNTRATb LINKARITY MEASUREMENT
- 74 -
preamplifier near the detector . A la rge dynamic range is specified
for these channels to provide adequate overlap with the intermediate
range channels.
(3)
Apart from other tes ts the dynamic range of these
channels was determined using a fission counter of sensitivity 1 cps /
nv and 100 me t r e s of mul t iscreen coaxial cable between the detector
and the channel in Apsara r eac to r . The response of the channel to
Apgara power is shown in Fig. 6 . 1 . 2 . The response is l inear upto
10 cps and count r a t e losses at 2 x 10 cps a r e less than 15%.
Analogue Reactivity Meter
Reactivity being one of the fundamental reac tor para
meters; , its measurement is important from the point of view of
both monitoring and safety. The analogue reactivity meter i s based
on the simulation of the inverse r eac to r kinetics by an electr ical
network represent ing the delayed and prompt neutron charac ter i s t ics
of the fissile components of the core . When a voltage proportional
to the neutron flux is applied to this network, the current flowing
out of this network is proportional to the product of the reactivity
and the flux. Hence in addition to the simulation network an elec-(4)
tronic divider forms par t of the instrument
Functional testing of the analogue reactivity meter
was car r ied out in Apsara r eac to r . The simulation network was
modified for delayed neutron groups of Apsara core . The reac t i
vity meter was connected to the l inear control channel output which
used a compensated ion chamber . The reac tor power was stabilised
at 50 watt keeping the fine rod in completely 'IN1 position. Fo r
finite successive withdrawals of the fine rod the reactivity was mea
sured by the analog reactivity mete r as well as by measuring the
- 75 -
reac tor period, taking ca re to stabilize the power with the help of other
rods before each subsequent withdrawal. The experiment was repeated
for two negative reactivity steps by insertion of the fine rod. The
resu l t s a r e presented in Table 6 . 1 . 1 .
TABLE 6 .1 .1
Measured and Computed Reactivities at
Different Fine Rod Posit ions
Fine Rod Position
(cm)
Reactivity Measured by analogue reactivi ty
meter (pcm)
Reactivity computed from reac tor
period (pcm)
0 to 16.3
16.3 to 24.7
24.7 to 35.6
35.6 to 64
64 to 28.5
28.5 to 0
+ 43.75
+ 62.5
+ 81.25
+ 65.88
- 123.75
-175
+ 44.9
+ 72.8
+ 83.3
+ 67.7
-126
-196
REFERENCES
1. D . B . Sangodkar, K. Pandurangan and C. Pa ramas ivam Pi l la i ,
"Neutron Detectors and Instrument Chc».m.els'J Activity Report
1975, RRC-19, pp. 65-67 (1977).
2. D . B . Sangodkar, Test Procedure for Prototype Boron Coated
Counter',' RRC-FBTR/DG/66513/DN-01 (1974).
3. V.A. Pe the , N . C . Rathod and C. Pa ramas ivam Pil lai ,"Design-
cum-Test Report on Prototype Start-up Channel'.' FBTR/FRG/
66213/DN-03 (1976).
4. V.A. Pe the , N . C . Rathod and C. Paramas ivan Pi l la i ,"Design-
cum-Test Report on Prototype Reactivity Meter" FBTR/FRG/
66223/DN-04 (1976).
- 76 -
6,2 Possibil i ty of Start-up of FBTR Without an Auxiliary Source (D.B. Sangodkar and K. Pandurangan)
A neutron source is normally used for reac tor s ta r t -up
to facilitate continuous and prec ise monitoring of the subcri t ical mul
tiplication. The adequacy of the source strength depends on detector
sensitivity and source detector geometry. With a view to circumventing
the problems of fabrication arid irradiation of ah auxiliary source., part icu
lar ly that of its re~irradiat ion in another "facility in the.event Of an unforseen
Shutdown Qf long duration, the adequacy of the intrinsic source of FBTR core
for the first s ta r t -up as well .as for any subsequent routine".start-up was studied. 5 ' "(1)
The. int r ins ic .source strength of a FBTR subassembly is 3" x. 10 n / s e c ' 240
assuming a concentration of 24.6% of Pu in the plutonium used in the fuel.
Based on the available detector locations in FBTR., the
count r a t e s obtainable from an in-core fission counter "and out-of-
vesse l B F 3 , boron-coated and fission counters were calculated for (2)
anticipated fuel loadings during the first approach to cr i t ical i ty
and for anticipated control rod movements during a typical routine
s t a r t -up . The minimum counting t ime required for favourable count
ing s ta t is t ics is tabulated in Tables 6 .2 .1 and 6 . 2 . 2 . This is de
fined as the minimum counting t ime which would > with 99% con
fidence, distinguish count-rates before and after loading a batch of
subassemblies .
Unfavourable s tat is t ics can seriously affect the
accuracy of c r i t ica l mass predicted by extrapolation. For. exam
ple , if the count before loading a batch of subassemblies is near
the higher s ta t is t ical limit and the count after loading the batch is
near the lower s tat is t ical limit',':, the difference in the two counts
would not t ruly represen t the reactivity change and would lead to
prediction of a higher cr i t ica l m a s s . It has been verified that the
maximum positive e r r o r in cr i t ica l m a s s predicted by extrapolation
- 77 -
of the first two inverse count ra te points from the incore detector
is four subassemblies . This e r r o r is progressively reduced as more
count r a t e points become available for extrapolation.
It is concluded that the minimum counting t ime is
adequately short (less than 100 seconds) and hence it would be
possible to start-up! FBTR without an auxiliary source .
TABLE 6 .2 .1
lies
is
sem
b
Sub
i
No
6
18
27
31
36
40
45
48
54
Expected
Keff
0.462
0.745
0.855
0.892
0.931
0. 967
0.984
0.999
1.02 8
Flux
4 xl 0 nv
0.72
1.11
1.67
2.22
3.84
7 .8
16.6
314
_
Count Rates and Minimum Counting Times
F i r s t
counte
Count ra te
cps
19
29
44
58
100
205
434
8350
_
Approach T
sion r
Min. time
sec
7 .3
o Crit icality
During •
Permanent Detector Locations
Flux
nv
0.972
0. 11
0.167
0.220
0. 384
0. 780
1.660
31.4
—
B F 3
Count ra te
cps
5
8
12
16
28
56
120
2290
_
Min. t ime
sec
23
Boron Counter
Count ra te
cps
Min time
sec
0.56
0. 88
1. 36
1. 76
3. 04
7.24
13. 6
24. 8 -
Fission Chamber
Count ra te
cps
Min. t ime
sec
0. 07
0.11
0.17
0.22
0. 38
0. 78
1. 7
3.1. 0
_
- 78 -
TABLE 6.2.2
Expected Count Rates and Minimum Counting Times During
Routine Start-up
Control Rod Position
Negative Reactivity
pern
Flux at perma -nent detector location
nv
Normal Startup fission chamber
Count r a t e
cps
Min. t ime
s e c
P r e Startup boron counter
Count ra te
cps
Min. t ime
sec
All CRs.down
Two CRs up
3 CRs up
4 CRs up
5 CRs up
Last CR ra ised
Last CR ^raised
Last CR. ra ised
Last CR ra i sed
Last CR ra ised
Last CR ra ised
Last CR ra i sed
8000
5400
3600
2400
1600
1100
750
500
330
220
150
100
0.54
0,67
1.00
10.55
2.18
3.2
4.7
7.0
10.0
15.0
24.0
35.0
0.54
0.67
1.00
10.55
2.18
3.2
4.7
7.0
10.0
15.0
24.0
35.0
965
47
4 . 3
5 .4
8
12
18
26
38
56
80
120
192
280
108
57
- 79 -
REFERENCES
1. D ,B . Sangodkar, K. Pandurangan, "Neutron Source for Startup
of FBTR" RRC-FBTR/FRG/66200/DN 06 (1976).
2. S.R. Paranjpe, D . B . Sangodkar and K. Pandurangan,"Poss ib i
lity of Reactor Star t -up Without an Auxiliary Neutron Source
With Par t i cu la r Reference to FBTR;' P r o c . of Symp. on Nucl.
React. Inst. BARC, Bombay (1976).
6. 3 Thermal Ageing of Leak-proof Cables for Containment Elect r ical Penetration (M. Sivanandan and D . B . Sangodkar)
The commonly employed technique for containment
e lect r ica l penetration is to cut the cable at the point of penetration
and to reconsti tute the signal/power t ransmiss ion path after inter
posing a leakage b a r r i e r such as epoxy res in . This procedure is
cumbersome, par t icular ly when the penetrating cables a re l a rger
in size and number. This can be simplified by the use of leak-
proof cables which utilise elastic insulating compound to seal the
interstrand and interconductor space.
To study the leak tightness of leak proof cables ,
test was performed on more than 50 samples and the cables were
found to give satisfactory resu l t s . Incorporation of leak-proof
cables for containment penetration requ i res evaluation of their
long- term performance. F o r th is , two separate programmes were
undertaken. F i r s t p rogramme involves re tes t ing of the cables
after a s torage life of three y e a r s . On test ing, the cables were
found to maintain thei r leak t ightness. Hence, it is inferred
that these cables have shelf life of more than 3 y e a r s .
- 80 -
The second programme involved estimation of the ther
mal life of the insulating (sealing) compound through accelerated ageing.
Procedures for estimating the thermal life call for life tests at several
temperatures above the expected normal operating temperature .
The Arrhenius equation which describes the temperature
dependence of the chemical reaction is used to approximate the re la
tionship between insulation life and temperature . An adaptation of
this equation to represent insulation life is
Log1Q (life) = A + B/T
Where A and B are' 'constants and T is the absolute temperature in.K.
The constants A and B can be estimated by fitting the experimental
data in the above linear equation. The log.. _ (life) versus 1/T
line obtained from the experimental data is extrapolated below the
range of tes t temperature, P rom this the life of insulating sample
for any required temperature can be obtained.
The test temperature for performing the experiment is
limited to less than 135 C by the softening temperature of PVC
sheath of the leak-proof cables. Eight samples of leak-proof control
cable of one metre length were bent in the form of a circle and
placed in the oven. The oven was heated to 130 C continuously for
8 hours per day. Periodically the samples were removed from
the oven and tested forvleak tightness. After leak testing, the cables
were further thermally aged. In this fashion the test continued
for more than 70 hours and the cables were found to maintain the
leakage integrity.
- 81 -
It is concluded that the sealing compound is stable even o
at 130 C. The leak tightness of the cable is not affected in storage
upto three y e a r s . It is difficult to predict the cable life by accelerated
thermal ageing since the cable cannot be subjected to temperatures higher o
than 130 C and below this temperature the cable life is long. REFERENCES
1. R. Prabhakar and D.B. Sangodkar, Leak-proof Cables for Contain
ment Penetration, Activity Report 1974, RRC-8 (1976).
2. Test Procedures for the Thermal Evaluation of Insulation Systems
for Electr ical Equipment, IEEE Guide 99.
3 . Statistical Analysis of Thermal Life Test Data, IEEE Guide 101.
6.4 Development of Ceramic-Metal Seals for Leak Detectors (A.S. Hunjan*, V.S. Raghunathan** and K. Govindarajan***)
Ceramic-metal seals (CM seals) , as shown in Fig. 6 .4 .1 a re
intended to be used as part of sodium leak-detectors in FBTR. CM seals
of other types a r e used to terminate instrument output cables at locations
where conditions of high temperature and radiation prevail .
The CM seal essentially consists of a central electrode and a
metallic coaxial body electrically insulated from each other by a ceramic
member . Further considerations a re the radiation levels and compati
bility with sodium environment. The operating conditions, for the CM
seals a re :
(i) Operating temp. : Normal 150 to 520 C
Maximum 550 C
(ii) P re s su re : Normal 110 to 120 MPa Test p ressure 500 MPa
9 2 (iii) Neutron flux : 4 x 10 n /cm - sec
4 (iv) Gamma flux : 10 R / h r
* Fas t Reactor Group ** Materials Development Laboratory
**# Materials Science Laboratory
- 82 -
TUBE N42
TUBE N 42
|, flIO
ALUMINA 7?\
? m
09
- 011 ,
00 fN4
en
SCALEI2'.1
FIG. 6.4.1, METAL TO CERAMIC SEAL FOR SODIUM LEAK DETEC TOR OF FB T R.
- 83 -
The leak detectors employing the CM seals will be mounted at loca
tions where the leaked sodium is likely to collect leading to the
shorting of the central electrode and the body. This gives a singal
for detection.
For use in FBTR, alumina was chosen as the ceramic
par t , aid a high nickel ferrous alloy (N-42) was chosen as the metal
member .
(1,2) Of the many methods * available for making CM
seals , the sintered metal powder process and the active alloy process
have. been. fairly thoroughly studied, and a variation of the former
method has been adopted in the present work because of certain ad
vantages.
In the present method, compounds of molybdenum and
manganese, namely ammonium molybdate, and potassium permanga
nate (20:1 by weight) a re dissolved in water containing a small
quantity of s tarch. This solution is applied uniformly over the
ceramic par t . Subsequent t reatment at 1050 C in wet hydrogen at
mosphere resul ts in a thin metalized layer (^ 20 ' r n ) on the
ceramic . On the metalized layer a thin coating (2-4 m) of nickel
is plated by an electroless plating process . After this operation
the ceramic is once again fixed in dry hydrogen at 850 C and after
re t r ieval from the furnace is ready for brazing. Tes ts will be
performed to ensure (i) uniformity of metalized layer and brazed
joint- (ii) leak tightness (iii) res is tance to thermal shock and (iv)
performance under sodium conditions.
- 84 -
REFERENCES
1. T=,S. Syunry, Development on Ceramic - Metal Seals for High
Power Klystron, KLP-1 (1973)
2. L. Reed, Electronic Ceramics , (The American Ceramic Soc.
(1969)) pp. 34-43.
3. A . H . Beck, Handbook of Vacuum Physics , (The Macmillan
Company 1964), Vol. 3 , Technology.
- 85 -
7. DATA PROCESSING SYSTEM FOR FBTR
7.1 Computer Supervision of Subassembly Outlet Sodium Temperature of FBTR (C. Boopathy and S.A. Weling)'
The design, development and testing-in-the.-simulated-
environment of a rea l - t ime software, namely the Sub-Program of Core
Temperature Supervision (SPCS), of the Central Data Processing
System, for supervision and safety monitoring of the core of FBTR
has been completed. The safety functions fulfilled by this program
a re 1) to detect as soon as possible the process of plugging leading
to the melt down of the subassembly,-. 2) avoid reaching the hot spot
temperature on the cladding of the fuel p ins , 3) protect the core against
undesired power excursions. It also detects the failure of the ther
mocouple. Computation of the parameters involved for the above
safety functions makes use of simple ari thmetic models . Safety
action (Scram) for .subassembly plugging is initiated on 2/2 logic
when both the thermocouples of the subassembly are in good condi
tion and failure of any one-thermocouple converts the logic to 1/1. •
The mean outlet temperature of the core and the mean
temperature drop across the core a re calculated by taking the average
of the individual subassembly outlet temperatures with the assumption
that the individual subassembly flows a re equal. Since there is going
to be four different flow zones in FBTR core, a suitable modification
in the software will be carr ied out in order to calculate the flow wei
ghted average. These two values a re supervised for clad hot spot tem
perature and power excursion, and appropriate safety actions a re t r ig
gered.
- 86 -
The plugging detection part of the software makes use of the
above said computed mean temperature drop across the core in
order to calculate the predicted temperature drop across the indi
vidual subassembly at all power levels. Triggering of a larm and
safety action depends upon the amount of deviation between the
predicted temperature drop and the actual temperature drop across
the subassembly.
Messages pertaining to the triggered safety actions (Alarm,
Lowering of Rod, Scram) are visualised on cathode ray display,
printed on line printer and operator teletypewriter.
REFERENCE
1. C. Boopathy, "Computer Supervision of the Core Outlet Sodium
Temperature of FBTR" Symp. on Nuclear Reactor Instrumen
tation, Vol.1, DAE, BARC (1976). •
7.2 Realisation of High Accuracy On-line Data Processing System for FBTR (P. Swaminathan and S.A.. Weling)
For effective measurement and control of plant pa ramete rs , it
is important to rea l i se adequate accuracy in the on-line data pro
cessing system. The accuracy of the on-line data processing sys
tem depends upon the accuracy of the Analog Input Sub System(AISS),
where the plant signals are received, multiplexed, amplified and
analog to digital converted under computer control.
The possible noise sources in AISS of the on-line data proces
sing system were studied. AISS is designed to minimise the effects
of noise sources . Flying capacitor technique is adopted to isolate
the plant ground from the computer ground.
- 87 -
To meet the required scanning r a t e , multiplexing is done at
two levels , one at low level using reed re lays for better accuracy
and another at high level using solid state switches. In low level
multiplexer, the input channels a r e further subgrouped to minimise
the crosstalk. Within AISS, opto-isolators a r e used for further
ground isolation. The input multiplexer rack is covered with cad
mium plated mild steel plates for minimising the noise coupling.
All the relay cards inside the rack and the signal carrying wires
a re well shielded.
The power supplies used for the on-line data processing
system, were found to influence the accuracy of the system. An
experiment was conducted to study the relative effect of differ
ent types of power supplies on the accuracy of the on-line data
processing system . It was found that the usage of linear - ^
power supplies in the place of switching-mode-regulated power
supplies improved the overall accuracy of the system. Subse
quently switching-mode regulated power supplies were replaced
with the l inear power supplies for the on-line data processing
system for FBTR. With these ar rangements , an overall accuracy
of bet ter than 0.1% is achieved for the on-line data processing
system for FBTR.
REFERENCE
1. P.. Swaminathan, "Realisation of a High Accuracy Analog Input
Data Acquisition System" Symp. on Nuclear Reactor Instru
mentation, DAE, BARC (1976),
- 88 -
7.3 On-line Diagnostics of the Central Data Processing System (P.Sreenivasan and S.A. Weling)
The on-line diagnostics program. for CDPS has been deve
loped and tested. It comprises of two parts viz. the main diagnos
tics and the auto control. .The former detects the faults, if any,
and the latter decides the remedial action and executes it. All
timing requirements are met through the rea l time clock which
interrupts the process every 31.25 m s .
The main diagnostics consists of a set of programs to diag
nose random faults, device faults and 'interrupt missing1 in I/O
operations. Periodic diagnosing is used mainly for ensuring the
functional fidelity of the CPU instructions.
The auto control part of the on-line diagnostics analyses
the faults indicated by the main diagnostics and decides whether
a switch-over to the standby system is warranted or not. In
case it is not needed, it decides to operate the system in r e
duced mode, by eliminating the failed submit and pushing in a
nearest substitute. The system software as well as the operator
will be informed of the situation.
In case of catastrophic failures like the "CPU fai lures",
the "Par i ty E r r o r " , the "RTC failure" etc. a switch-over to
the stand-by system is initiated. The switch-over logic circuit
detaches the failed system from the plant environment and
brings in the stand-by to its place. The stand-by system is
alerted by an interrupt, and it takes over the on-line respon
sibility immediately.
REFERENCE
1„ P . Sreenivasan, "On-line Diagnostics for a Real Time Computer :..•
System"Symp. on Nuclear Reactor Instrumentation, Vol. L ,
DAE, BARC (1976).
- 89 -
8. REACTOR OPERATION STUDIES
8.1 Transient Study of Feed Water Heating Cycle in FBTE (C.Raju and S.S. Kumar)
Loss of steam supply to the feed water hea te rs , resulting
due to tripping of the turbine and non- availability of live steam
from the bypass line can result in the reduction of Net Positive
Suction Head (NPSH) available to the pumps. In FBTR, there a re
three contact type feed water heaters in s e r i e s , the high p re s
sure heater being the deaerator . The loss of steam supply also
results in an increase in the pressure differential across the
trays in the case of deaerator and LPH-II (Low Pre s su re
Heater-II). The effect of steam cut-off to all the three heaters (2)
simultaneously* has been studied in detail. This has been done
with a view to finding whether the NPSH requirements of the
pumps are met during this incident. It was concluded that the
NPSH requirement is not met after about. 4' seconds'. Some pos
sible solutions to this problem were analysed and the injection of
cold condensate in the suction piping of the main boiler feed (3) pump was found to be an effective solution
REFERENCES
1. C. Raju and S.S. Kumar,'Effect of Steam Cut-off in FBTR Deae
ra to r , PPD (75-11-6), Symp. on Power Plant Dynamics and Con
t ro l , DAE, BARC (1976).
2. C.Rajui'A Note on Transients in LPH-II and Deaerator and their
Effects on NPSH to Pumps" RRC-FBTR-FRG/66027/2 (1976).
3. C.Raju,"Some Prel iminary Solutions to NPSH Problem of Main
Boiler Feed Pump',' RRC-FBTR-FRG/66027/3 (1976).
- 90 -
8. 2 Safety Act ions for Some Incidents (G.Vaidyanathan and S .S . Kumar )
Des ign of p ro tec t ion for t h e FBTR plant involves c o n s i d e r a
b le amount of a n a l y s i s . Some of t h e s e incidents amenab le to ana
ly s i s by t h e 'FBTR Dynamic Code' have been s tudied. Among
o t h e r s , t h e incidents of fa i lure of t h e p r i m a r y and secondary s o
d ium pumps have been studiedo T h e s e incidents without any safety
ac t ions could cause e i t he r damage o r fatigue to the components
and flooding or dry ing of the s t e a m g e n e r a t o r . Some safety ac t ions
have been proposed to o v e r c o m e t h i s . The p roposed safety ac t ion
c o n s i s t s of two types : (i) act ion to p ro t ec t t h e c o r e Ci-i) sympa the
t i c ac t ion to r e d u c e t h e r m a l shocks in equ ipment s .
R E F E R E N C E S •
1. Ashok K u m a r and S .S . K u m a r , P r o c . S y m p . P o w e r P lan t Dyna
m i c s and Cont ro l , D A E , BARC, 192 (1976)
2. S«S. K u m a r , S. B h a s k a r P e r i a s w a m y , R. Chandramohan ,
A . S . Dix i t , D . B . Sangodkar and G.Vaidyana than , "incident
Ana lys i s and P r o t e c t i o n Chain for FBTR" R .RC-FBTR-FRG/
66040 (1976).
8 .3 A P r o g r a m for P a r t Load Opera t ion of FBTR. P l a n t (A. L . Ko thanda raman and S. S» Kumar )
Seve ra l r e s t r a i n t s a r e to be sa t is f ied for a p r o p e r opera t ing
mode for FBTR plant . One mode of s teady s t a t e opera t ion s u g g e s
ted e a r l i e r had the d i sadvan tage of low t e m p e r a t u r e dif ference
of hot s econda ry sodium and s t e a m , which may pose p r o b l e m s of
c o n t r o l . A l s o it is poss ib le that a high t e m p e r a t u r e of cold secon
d a r y sod ium in the s t e a m g e n e r a t o r may lead to w a t e r boi l ing a t (2) i ts inlet . With t h e s e obse rva t ions in mind a new opera t ing mode
(3) h a s been developed. A. c o m p a r i s o n h a s been made be tween th i s
- 91 -
Hiode and the earl ier one, based on the changes in the different
parameters of the steam generator as the steady state power is
increased. This operating mode is characterised by constant p r i
mary and secondary sodium flows for a given final power.
REFERENCES
1. S.S. Kumar , A. L. Kothandaraman and T . Devanath,"A Static
Model for the Fas t Breeder Test Reactor Plant" RRC--13
(1976)
2. A. L. Kothandaraman,"Fonctionment-2" RRC-FBTR-FRG/66030
(1976).
3 . G. Vaidyanathan," A Comparison of Fonctionment-1 and Fonc-
tionment-2',' RRC-FBTR-FRG/66030 (1976).
- 92 -
9. REACTOR CHEMISTRY
9. 1 Hydrogen Removal from Sodium (P . Rajamani and R. Subramanian)
Impurities in sodium a r e of major concern due to their influ
ence on corros ion , induced activities and pipe line plugging. The
allowable limit-of impurities a r e specified at ppm levels . Of these ,
hydrogen is one of the major impurities causing plugging of l ines
in the various par t s of the system. The assessment of equilib
r ium distribution of hydrogen between sodium and the inert cover
gas in closed sys tem, analysis of the different methods of r emo
val and the selection of an economic method have been carr ied
out in connection with the purification of commercial sodium to
reactor grade.
The factors that influence hydrogen solubility in sodium
a r e t empera tu re , part ia l p r e s su re of hydrogen in the gas flow
and the dissolved oxygen in sodium. A soluble O-H species is
in equilibrium with hydrogen in the cover gas . However, de
composition of sodium hydride is the most important reaction
in Na-H-O system around 300 C and the NaH-H equilibrium
involves the prediction of the dissociation p re s su re of NaH.At
low concentrat ions, hydrogen remains in solution in sodium and
is in equilibrium with the gas phase. At high concentrations
and at moderate t empera tu res , two condensed phases exist viz.
a hydrogen - saturated liquid metal phase and a solid hydride
phase. Finally, at hydrogen concentrations approaching 50%,
only a sodium saturated solid solution of NaH exists in equi
l ibrium with hydrogen in the gas phase.
- 93 -
Sodium, hydr ide has a low t h e r m a l s tab i l i ty . T h e hydrogen p r e s
s u r e over d i s soc ia t ing sod ium hydr ide is 1 a t m . a t 420 C. In a c l o
sed s y s t e m , the equ i l ib r ium p r e s s u r e of hydrogen is de te rmined by
the t e m p e r a t u r e of sod ium, m a s s of sod ium, volume of gas phase
and the to t a l concen t ra t ion of hydrogen . The equ i l ib r ium r e a c t i o n in
the unsa tu r a t ed r eg ion can be e x p r e s s e d a s
Na( l ) + i H (g) ^ = ^ = NaH (unsa tura ted) (1)
T h e equ i l ib r ium constant for the above r e a c t i o n is
K =S iaH_ i (2) ^Na(P.H2)2
W h e r e ' C is the concen t ra t ion and ' P ' is the p a r t i a l p r e s s u r e . A s s u
ming ideal behaviour of hydrogen in the gas phase and solving for
hydrogen concen t ra t ion in the l iquid p h a s e , t he following exp re s s ion
is obtained.
C H " A « ( C H - C H ' ( 3 )
w h e r e C K = Concent ra t ion of hydrogen in sod ium
CL. = weight f rac t ion of to ta l hydrogen in the s y s t e m
r e f e r r e d to the weight of sod ium.
A = K 2 R T
Q = M a s s of sodium Volume of gas p h a s e
F u r t h e r , subst i tu t ing A r r h e n i u s equation for the equ i l ib r ium constant
( i . e . K = K e ) and dif ferent ia t ing over t e m p e r a t u r e , the follow
ing equation r e s u l t s .
A C H - | ( C ° H - C H ) K2o R & e 2 E / R T ( 1 M ) ( 4 )
d (C w + Ad ) * - l
H —2
Since a l l the t e r m s a r e pos i t ive the n a t u r e of va r i a t i on is d e t e r
mined by the t e r m (1 —-p^,).
- 94 -
If 2E > RT, dissolved hydrogen concentration in sodium decreases
with increase of temperature . If 2E «/ RT, increase of temperature
leads to an increase of dissolved hydrogen concentration. This tran
sition tempera ture , is calculated to be 1000 K-
The hydrogen removal r a t e s of various processes is given
below:
a. Inert gas purging: The factors that influence mass transfer a re
purge r a t e , volume of gas phase, density of the purge gas ,geo
metry and temperature of sodium. Solving the differential equa
tion for ra te of removal and equilibrium decomposition, the fol
lowing equation is obtained,
V, t =
SK« X X „ T> v
2 -JL I s
TV X 2 X ,
(5)
S - Purge ra te
V1 = Volume of sodium
V_ - Volume of gas phase
Purging t ime g
K..- Equilibrium constant
X1 - Initial concentration of hydrogen in sodium
X - Final concentration of hydrogen in sodium
b. Evacuation
In this method, the maximum possible vacuum is applied at
the specified temperature and the hydrogen is removed. The equa
tions for the t ime of evacuation to the final p ressure (eqn. 6) and
mass of hydrogen removed (a modified form of eqn. 5) are to be
solved simultaneously to obtain the required: parameter . V P
T = In 2_1_ (6) S P„
av 2
- 95 -
•where 3
V = Volume to be evacuated, m
P 1 = Initial p ressure
P = Final p ressu re
S = Average pumping ra te m 3 / h r .
The removal of hydrogen in sodium, present as NaH, is pos
sible by thermal decomposition only below the transition temperature .
The decomposition of NaH and removal by argon purging takes more
t ime. The operating cost to maintain the temperature and high inert
gas consumption ra te over the period renders this process costly.
Besides, it may be difficult to achieve good mixing in argon sweep
ing. Evacuation accomplishes the same duty in a shorter period and
very economically. It has been estimated that the total cost is r e
duced by a factor of 20 if evacuation process is adopted. Hydride
decomposition at 350 C with simultaneous evacuation at 1 mm Hg
pressure resul ts in acceptable levels of hydrogen in sodium for
reactor applications.
REFERENCES
1. S.A. Meachem, F . F . Hill and A.A. Gordus, "The Solubility of
Hydrogen in Sodium", APDA-241 (1970).
2. O.J. Foust (ed.) , Sodium-NaK Engineering Hanbook, V o l . 1 ,
Sodium Chemistry and Physical Proper t ies , (Gordon and Breach,
Science Publ ishers , Inc . , New York 1972).
- 96 -
9. 2 Estimation of Hydrogen in Sodium (V. Nirmal Gandhi, T . E . Mahalingam and N . P . Bhat)
Considerable work has been done on developing an ana-(1-3) lytical method for the determination of hydrogen in sodium
We have adopted the method of Meachan and Hill which' is 'the most
recent one reported. This method differentiates between hydrogen
due to hydroxide and that which is present as hydride in dissolved
form.
In this method, a two-stage vacuum reflux technique
is employed with mercury as the refluxing medium. The hydrogen
evolved is measured quantitatively by gas chromatograph. The m e r
cury acts as a sequestering agent removing the highly reactive sodium
from the system by amalgamation, thus preventing the re-formation
of sodium hydride by the liberated hydrogen.
The experimental set up (Fig. 9,2.1) consists of a reflux
vessel and a high vacuum system employing a diffusion pump and a -4
rotary pump capable of giving a vacuum of the order of 10 T o r r .
The argon gas used for venting the vacuum system after refluxing
is over, is thoroughly dried by passing it through a molecular sieve
t rap and a cryogenic t rap at - 90 C. The high vacuum system and
the purification step have been found to be necessary to control the
blank. The blank contribution from the vessel could be reduced to
a satisfactory low level of 0.1 microgram of hydrogen, by refluxing
the amalgam three t imes at 360 C. After the blank is reduced, the
sodium sample taken in the side a rm of the reflux vessel is allowed
to drop into the amalgam in.vacuum. The amalgam is refluxed at o -4
200 .C in a vacuum of 10 to r r for 15 minutes and the vessel is
brought to atmospheric p ressure with pure -argon. A sample of the
gas in the vessel is injected into the gas chromatograph and the hy
drogen estimated. Hydroxide hydrogen is estimated by carrying out
S£PTt>n SUCTION
PORT
PENNING 6 A USC
2?
ARSON > [- PR/£D BY
MOL. SIEVES.
FROZEN AC£TON£ T£AP-
J*£PCUgY "MA/VOM£T£K
s.SOOtUM SAMPLE.
^
AMAL GAM A T/OA/& R£FLUX V£SS£L
AMALGAM.
D
4
7-MAP.
To OIL DIFFOS/ON"
^PUMP AA/D HOTAKy
VACUUM PUMP-
FIG.9.2.1 EXPERIMENTAL SET UP FOR HYDROGEN ESTIMATION
- 98 -
the refluxing at 360 C under a vacuum of 500 to r r .
REFERENCES
1. G. Goldberg, "Determination of Hydrogen in the Alkali Metals",
Analytical Chemistry Division Annual Progress Report, ORNL-
3397 p. 52 (1962).
2. S.A. Meacham and E . F . Hill , "The Determination of Hydrogen
in Sodium Metal", APDA-183 (1966).
3. G. Naud and J. Sannier, "Analysis of Hydrogen in the F ree
State or as Hydride in Sodium", Bull. Soc. Chem. , 2735-37,
(1963).
9.3 Flame Photometric Estimation of Lithium and Potassium in Nuclear Grade Sodium. Metal (D. Krishnamoorthy, T. B . Mahalingam and N . P . Bhat
Lithium is a potential neutron absorber and needs to
be controlled below 10 ppm level in sodium. Potassium is a common
impurity in sodium and is also to be monitoried. Methods reported
in l i terature for these estimations suffer from limitations of poor
sensitivity and cumbersome experimental procedures.
A simple and accurate method has been developed
where the weight of the sample needed is one gram only. Sodium
which interferes in the flame photometric estimation of Li and K
is precipitated as sodium chloride from saturated hydrochloric
acid solution and the filtrate is used for the estimation of lithium
and potassium. The concentrations of lithium ( 0 . 1 - 1 . ppm) and
potassium(100-500- ppm) a r e too low to cause any precipitation and
hence they remain in solution.
- 99 -
Bausch and Lomb's AC-2-20 model Atomic Absorption .
spectrophotometer was used in its emission mode for the estimation.
Emission intensities were measured for different standards of lithium
(0.1-1 ppm range) and potassium (0.5-4 ppm range) and calibration
curves were drawn. The slame conditions and calibration data a r e
presented in Table 9 . 3 . 1 .
A stock solution of the sodium sample was prepared by
dissolving sodium in methanol. The exact amount of sodium was
determined by t i t r imetry. 20 ml of the sample was 'taken in a
beaker, 20 ml of cone. HC1 added and the solution saturated with
hydrogen chloride gas . The precipitatp of sodium chloride was fill-
tered and washed with cone. HC1. The filtrate was evaporated to
dryness and the'dried mass dissolved in demineralised water to a known
volume. This solution was subjected to flame photometric analysis.
Standardisation was done by adding known amount of li
thium and potassium standards to the sample solutions after dissolu
tion of sodium, riecovery was checked by following the above procedure.
The resul ts a re presented in Table 9 .3 .2 .
The standard addition data reveal that full recovery of
potassium and lithium is obtained and that there is no loss in the process
of separation. The method is quite precise as evident from the rela
tively small coefficient, of variation !(2%) obtained in the analysis of
sodium samples.
3FERENCES
1. R . B . Hinze, "Sodium Purity Requirements: A Review and
Evaluation',' NAA-SR-Memo 12394 (1967).
2. L . B u r r i s , F .A . Cafasso, R.J . Meyer, M.H. Berkeley and
H.S. Edwards, "Interim Methods for the Analysis of Sodium
and Cover Gas ' , ANL-ST-6 (1971).
- 100
TABLE 9 .3 .1
F lame Emission Calibration Data for Potass ium and Lithium
Potassium
Wave length
Band Pas s
767 nm
2.0 nm
Lithium
Wave length
Band Pass
670.8 nm
2.0 nm
Air P r e s s u r e
Ai r flow-
Acetylene
p res su re
Acetylene flow
Flame Conditions
1.6 kg /cm Air P r e s s u r e
486 1/hr Air flow
0.9 kg /cm
54 1/hr
Acetylene p r e s s u r e
Acetylene flow
1. 8 kg /cm
486 1/hr
e
0.7 kg / cm '
70 1/hr
Concentration of Potassium
(ppm)
4 . 0
3 .0
2 .0
1.0
0 .5
Intens
100
81
56
30
15
Calibration
Concentration of Lithium
(ppm)
1.0
0 .7
0 .5
0 .2
0 . 1
Interi
100
70
50
20
10
-101
TABLE 9.3 .2
Estimation of Lithium and Potassium in Sodium
a) Standard addition data for lithium
Lithium in the sample Lithium added
pg
Total found
pg
Lithium recovered
ug
1.7
1.7
1.7
0.5
1.0
1.5
2.15
2.70
3.15
0.45
1.00
1.45
b) Standard addition data for potassium
Potassium added Potass ium in the sample
pg "g
Total found
ug
131
180
280
Potass ium recovered
F g -
48 .
97
197
83
83
83
50
100
200
c) Analysis of sodium samples • \
Sample Number Lithium (ppm) Potass ium (ppm)
1
2
3
4
Standard deviation for sample 4
0.47
0.54
0.89
0 . 9 7 , 0 . 9 8 , 0 . 9 8 , 0 . 9 8 1.01
I for 0.02
iation (%) 2
97
194
143
143,147,147, 151
3
2
-102-
3, L. Silverman, The Determination of Impurities in Nuclear Grade Sodium Metal, (Pergamon P r e s s 1971),
9,4 Purification of Commercial Sodium to Nuclear Grade (P. Rajamani and R, Subramanian)
The sodium circui ts of FBTR requi re a total inventory of
150 tonnes of sodium. The impurity levels have to be kept at very low
levels to minimise corrosion, plugging, induced activity and neutron
absorption. Hence, work on the purification of commerc ia l grade sodium
(*J 99.5% pure) to nuclear grade (impurities <• 120 ppm) has been taken
up. The bulk impurit ies will be removed by coarse and microfil ter
assembl ies . Specific impurit ies like calcium, hydrogen, and oxygen will
be removed by oxide slagging, vacuum decomposition and cold trapping
respect ively.
The process consists of five stages viz, melting of the brick
sodium, filtering through filter ba t te r ies , calcium removal , hydrogen
removal and final purification with cold t r ap in a separate purification
r ig . The purified sodium will be t ransported to the r eac to r site and
charged into various sys tems.
Two purification s torage tanks of 30 tonnes capacity e ich are
used to receive the sodium and pass it through the loop. The loop
essentially consists of an electromagnetic (EM) flow meter , an exchan-
ger-economiser , a cold t r ap , a plugging indicator and an expansion
tank (Fig. 9, 4. 1), The EM pump continuously ci rculates the sodium
through the • loop, the flow ra te being measured by the EM flowmeter.
The plugging indicator will measure the plugging tempera ture at the
inlet and outlet of the cold t rap which is cooled by air circulating in
its finned jacket. The exchanger-economiser reduces the heat load
of the cold t rap and controls the sodium tempera ture at the cold t r ap
| n « M „ . 7 |
!""^T OB '«,..«? Ni l WOOIM
AOCDM CVIMOC R
T t A M ' t t IMC L-.i I
g^Jgl
'•fi- «1
t lCNAttt f t CCO«««l1KR
cooiwt no »*r
» .flOW MfTII.
1K« Al t UNK
» « • • »AMPUat
IECEK0 vi n n u o i I A I V C
VI tta SAMrilK HM( VAUf
11 CM n m * tut no* use VAIVC
V i COLO Tt iP OV n i t VALVt
V I riCH (CO IV M l f MIVC
Vti7 V41VIS MR U H r t l H ,
v i J vALvci to s u m v •« TO 01
n . • • KtnjitH I I K M I V C roo« Pt
Vtf MAIR C0•«Ml VAIVC
vtt * t c r w a iimt V A I V I fMoroartfOl
vi) cott iftAP mitx mtv t
FIG.9 .4 .1 . PURIFICATION LOOP FLOW CHART
o I
-104-
inlet. A flow-through sampler is provided to take samples for chemical
analysis. This r ig will provide experience in sodium handling and in the '
operation and maintenance of high inventory sodium loops.
9- 5 A Vacuum Distillation Facili ty for Sodium (V. Ganesan, P. Rajamani and N. P . Bhat)
For the estimation of oxygen and metallic impurit ies in (1 2)
sodium, vacuum distillation technique has been widely accepted ' . In
this method, sodium is distilled in high vacuum and the residue analysed
for various impuri t ies . Such a facility has been set up in the Chemistry
Laboratory.
The apparatus for the vacuum distillation of sodium, as
shown in Fig. 9. 5.1 consists essentially of: (i) sodium distillation
vesse l and (ii) High vacuum system.
The sodium distillation vessel , shown in Fig. 9. 5. 2 is made
of stainless steel and has a cold finger capable of collecting and re ta in
ing the distilled sodium. The cold finger is kept at a temperature of
around 40-50 C by circulation of cooling water. Four crucibles of 20
ml capacity can be introduced into the distillation vessel by means of
a holder. The sodium sampling operations a re car r ied out inside an
iner t atmosphere glove box.
In the distillation of sodium, high vacuum needs to be
maintained to ca r ry out the distillation effectively at lower tempera
tu res and also to obviate any possible contamination of sodium during
the distillation. In the apparatus, a high vacuum tra in consisting of
an oil diffusion pump (100 l i t res capacity) backed up by a ro ta ry vacuum
•If :£$}
i I .'•"•!. n 0
0 PE.NN1HG GAUGE
THERMOCOUPLE GAUGE. .
SODIUM DISTILLATION • VESSEL
RESISTANCE PURUACE
COOLING COILS.
OIL DIFFUSION PUMP
LNT
^
} £ t
=cSj=
.ISOLAT/OA/ VALVE
JZOTAXy PUMP.
FIG.9.5.1. SCHEMATIC OF VACUUM DISTILLATION SYSTEM FOR DETERMINATION OF
OXYGEN AND TRACEMETALLIC IMPURITIES IN SODIUM
Water
Water
Cold finger-
Crucible-
c =
0 0 c 0
5& i i! II I U I i
i i — • i 1
L \T7 V7 , .
D yv1"*—Diaphram valve
Cooling coils
•Thermocouple
-Crucible holder
FI6.9.5.2. SODIUM DISTILLATION VESSEL.
-107-
pump and a liquid nitrogen t rap a re employed to achieve a vacuum of -5 the order of 10 to r r . A thermocouple gauge and a cold cathode
penning gauge are provided for vacuum measurements . The distilla
tion vesse l i s placed inside a cylinderical res is tance furnace and it
is found that the distillation of sodium gets established at. about 325 C
at the above-mentioned vacuum conditions. The temperature of dis
tillation is measured using a stainless s teel sheathed chromel-alumel
thermocouples kept in contact with the crucible holder. The tempera
ture of the furnace is controlled within ± 5 C using a temperature
controller .
The facility is being regularly used in the analyses of
samples from the operating sodium sys tems. The distillation is
found to occur smoothly and a 6 g sample of sodium takes roughly
4 h r s . for the distillation. The completion of the distillation is
ascertained by a sudden r i s e in the vesse l tempera ture .
REFERENCES
1. J . R . Humphrey J r . , 'Sampling and Analysis of Impurities in
Liquid Sodium Systems' , Chem. Engg. Prog. Symp. Series ,
American Institute of Chemical Engineers, N. Y. 53+(20), 7
(1957).
2. T .R. Ramachandran and W.A. Harcland, "Determination of
Metallic Impurities at ppb-ppm Level in Sodium",
ANL-7668 (1970).
- 108 -
9.6 A study of Indigenous Molecular Sieves for the Drying of Argon (S .C.Sekar , S. Rajendran Pi l la i and R. Subramanian)!
Molecular sieves a r e universally used for the drying of
various gases . In view of the lack of data on the indigenously available
molecular s i eves , an experimental p rogramme was carr ied out to
generate data on their drying charac te r i s t ics . This work was done with
specific reference to the drying of argon which is used as cover gas
in sodium sys tems . Table 9 .6 .1 gives the physical proper t ies of the
indigenous molecular s ieves .
The experiments were ca r r i ed out to generate data that
would enable design of fixed bed d rye r s using the widely accepted
mass t ransfer zone model . As per the model, the height of the
mass t ransfer zone (Z. ) is given as
9A ZA " Z"
where Z = height of the adsorption bed.
0_, = Time at exhaustion of the bed.
0 _ = Time at breakthrough.
@. = Time required for the mass t ransfer zone to move its own height.
•j = Fract ional abi l i ty of the adsorbent in the mass t ransfer zone to absorb solute at the breakthrough point.
All the above paramete rs were deduced from experimentally obtained
plots of effluent mois ture concentration (Y) vs . t ime using the method
described in ref. (2).
- 109 -
The lowest moisture content obtainable during an adsorption
operation depends on the residual moisture content of the bed. Th is ,
TABLE 9 . 6 . 1 .
Physical Proper t ies of the Adsorbent 'SELECTOSORB' -4A
Nominal Pore diameter
Form
Bulk density
Crush strength
Loss on attrit ion
0.4 nm
1.5 mm extruders
0.7 kg/1 2
4 . 5 - 5 kg /cm 0.5%
in turn , depends on the moisture content of the gas used for regene
ration and on the regenerat ion t empera tu re . A moisture measure
ment apparatus working on the principle of the low p res su re method
was used in the measurements of moisture content of argon.
The equilibrium absorption capacity of the molecular
sieves was obtained by equilibrating a known weight of molecular
sieves with argon of known moisture content and estimating the in
c rease in weight of the molecular sieves due to the adsorption of
mois ture . The moisture content of the argon, which needs to be va
r ied to get the adsorption charac ter is t ics is manipulated by passing
a portion of the gas through water .
The breakthrough charac ter i s t ics of the adsorbent were
obtained with a fixed bed column of dimensions given in Table 9 . 8 . 2 .
The molecular sieves were first regenerated at 300 C with argon as
purge gas and the completion of regeneration was ascertained from
the mois ture content of the effluent. The bed was subsequently
cooled and the adsorption operation started by-passing argon in a
direction counter-current to that adopted during regeneration. The
effluent moisture content was then followed until the bed was exhausted.
- 110 -
The regeneration charac ter i s t ics of the absorpent were
obtained for different t empera tures and for different moisture levels
in the purge gas during regenerat ion.
TABLE 9 .6 .2 .
Results of Dynamic Experiments
Flow ra te of argon
Weight of molecular sieves
Length of the column
Diameter of the column
Average tempera ture during the experiment
450 ml /min .
25.3214 gm
40 cm.
1.0 cm.
27 C
„„ ,. Outlet Moisture Content Time /hour vpm
0
1
3
4
7
10
12
16
24
27
52
76
365
381.5
445.5
516.5
13
11
11
13
11
17'
13
17
13
13
15
11
11
13
13
13
- I l l -
„ Outlet Moisture Content ime/hour vpm
538.5
548
557
571
573
574
579
585
589
13
15
40
64
93
132
176
217
217
The data obtained are presented in Table 9 .6 .2 and in
F igs . 9 .6 .1 to 9 . 6 . 4 . A comparison, of the adsorption isotherms
for the indigenous molecular sieves and the Linde (Union Carbide) (2,3)
molecular sieves * is shown in F ig . 9 . 6 . 1 . The height of the
mass t ransfer zone was estimated as 3.305 cm. at a superficial
velocity of 9.545 c m / s e c . comparing favourably with the reported
values of about 5 to 7. 5 cm. for Linde (Union Carbide) molecular
s ieves . Small off-normal deviations were observed and this could
be attributed to extraneous limitations in the moisture measurements .
The resu l t s of the regenerat ion experiments in F igs . 9 .6 .3 and 9 .6 .4
show the effects of tempera ture and moisture contents of the gas
used for regenerat ion.
On the basis of experimental data, the drying charac
te r i s t i cs of indigenous molecular sieves were generated towards the
design of argon drying uni ts . The studies have shown that the indi
genous molecular sieves a r e comparable to the Linde products in such
applications.
- 112 -
in ui a in J o 2
E w o o
o r* X
«/> Ui > UI 55
o X u. o
I u z o
6 9
20
18
16
H
12
10
8
6
2
t t » * C
X X .L I 400 800 1200. . 1S00 2000 2400
MOISTURE CONTENT OF ARGON (Vom> -
2800
FIG.9,6.1. COMPARISON OF ADSORPTION DATA
280
240
z o
< en t— z u u z o u
200
160
120 -ui _ i
o
80
40 -
00
. 240 280 320 360 . 400 440
TIME (HRS)
480 520 560 •500
FIG.9.6.2- RESULTS OF DYNAMIC EXPERIMENTS
- 114 -
in ui > UJ
20
18
16
12
10
8
6
4
2
0 200
TEMPERATURE (-(f)
FIG.9.6.3. RESULTS OF REGENERATION EXPERIMENTS
- 115 -
TEMPERATURE ((f)
FlG.9.6.4.EXPECTABLE OUTLET MOISTURE CONTENT IN ARGON
REFERENCES
- 116 -
1. G.M. Lukchis, Chem. Engg. _80, June 11 , 111 (1973).
2. A. Draycott and A . C . K e r r , "Purification of Carbon Dioxide
for Reactor Purposes , Pa r t III. Drying", AAEC-E85 (1962).
3. "Union Carbide Molecular Sieves for Selective Adsorption" BDH
Catalogue, Third Edition, Third Impression (Revised) (BDH
Chemicals Limited, Poole , England).
9. 7 An Exper iments! Study of. the Chloride Incursion Character is t ics of Proposed Thermal Insulation Mater ia ls due to Thermal Cycling (P . Rajamani and R0 Subramanian)
Stress corrosion cracking of stainless s teel equipments
and components in p r o c e s s industries located in coastal a reas has
been reported . In most of the fai lures , the reason attributed is
the pickup of chloride from atmosphere and its progress ive move
ment through the insulation to the surface of the pipe. This pheno
menon, external s t r e s s -co r ros ion cracking (ESCC) is reported to
occur in the temperature range 50 - 200 C . With the F a s t
Breeder Test Reactor (FBTR) of the centre being located in close
proximity to the sea coast , the problem needed to be specifically
investigated. The operating tempera ture of FBTR.. secondary system
is about 45 C with a minimum tempera ture of 150-160 C being
maintained during startup and shutdown operations. During the
life t ime of the r eac to r , approximately 300 thermal cycles a r e
envisaged. Hence, it is essential to tes t the insulation for its
propensity to induce external s t r e s s corrosion cracking by the in
cursion of chloride from the atmosphere.
During startup of the sys tem, a i r will be expelled from
insulation due to heating and during the course of shutdown atmospherite"-
- 117 -
air will rush into the insulation. The chloride incursion depends on
the difference between the mean tempera tures of the insulation du
ring normal operation and shutdown conditions. The mass of a i r
that will pass through the insulation per cycle per unit length of
the system is equal to the product of porous volume of the insulation
and the density difference of a i r at the mean tempera tures .
An experiment was conducted to establish the chloride
penetration profiles by sucking the atmospheric air through the in
sulation under accelerated conditions simulating the total a i r -b rea th
ing of a pipe insulation during the lifetime of the r eac to r .
The experimental set up consisted of a perforated PVC
pipe, two insulation layers (the inner one being a high tempera ture
insulation), flow meter , suction pump and a manometer . The ex
periment was conducted in open air for a period of 24 hours with
air suction at the ra te of 18 l i t /min . (NTP) and the total a i r sucked 3
in was 26 m . The porosi t ies of the insulations were 0.932 and 0. 955 for the high tempera ture and low tempera ture insulations
respectively.
The analysis of the samples at the end of the experi
ment revealed a mean r i s e in the chloride level by 14 ppm over
the blank chloride levels ear l ie r estimated. F rom the radia l d is
tribution of chloride in the insulation as shown in F ig . 9 . 7 . 1 , it
can be seen that the chloride concentration dec reases to the blank
level of the fresh insulation at a radial distance of 6.5 cm. from
the pipe surface. The chloride level in the surface layers of in
sulation was found to be around 44 ppm.
In spite of the fact that the experiment was conducted
under accelerated conditions, and with six t imes more a i r passing
through, the chloride incursion was found to be limited only to the
I
S 6 r
50
4 0 -
• 3 0 -
20
Pipe surface
Insulation thickness:-IS-6cm
10 15
Blank level
20
Radial distance from the centre of the pipe ( cm)
03 I
2S
FIG.9.7.1. CHLORIDE PROFILE IN THE INSULATION
- 119 -
outer layers of the insulation and not reaching the pipe surface pro
per . This amply proves that with our existing insulation, the prob
lem of atmospheric chloride penetration through the insulation is
not a mat ter of concern throughout the lifetime of the r eac to r .
REFERENCES
1. W.G. Ashbang, Materials Protection, May (1965), p . 18.
2. 'Nonmetallic Thermal Insulation for Austenitic Stainless
Steel ' , USAEC Regulatory Guide 1.36 (2/23/73).
9. 8 A Low P r e s s u r e Method of Moisture Determination in Gases (S. Rajendran Pi l lai , S.C. Sekar and N . P . Bhat)
Estimation of moisture content in gases is of great im
portance in reac tor applications. Different methods a r e reported
(1,2 3)
in l i tera ture ' . In the method adopted by u s , moisture is se
lectively condensed from the gas s t r eam and later evaporated. The
p ressu re developed due to this moisture is me asured by an oil mano
meter . Suitable correct ions a r e made for the non-ideality of mois
ture before calculating the moisture content from the manometer
reading.
The apparatus is as shown in Fig . 9 . 8 . 1 . The appa
ratus is connected to the cylinder (1) containing the gas whose
moisture content is to be estimated through a venturi flowmeter (2) .
T1 and T are two magnesium perchlorate t raps incorporated to
eliminate moisture contamination from the atmosphere. The cryo
genic t raps (3) and (4) a re provided for the condensation and r e -
condensation respectively of the- moisture from the gas s t r eam.
Liquid nitrogen-acetone s lu r ry is employed for the condensation.
The manometer (5) filled with apiezon oil is used to measure the
2
j.GAS CYUN2ER
2. VEMTUR/ FLOWMETER.
3S4CPyOGEA//C TRA PS .(ACETONE + L/QU/D NITROGEN). 5. O/L MAMOMETE-fi. 6. L/QU/D M/TROGEN TRAP.
7-ROTARY VACUUM PUMP ASSEMBLY
T,&T2Ma6NE3IUM PERCHLORATB TRAPS. .
BtMz8UL8S OF . KA/OMN VOLUMES.
S7 . Sz ,S3 . S4 . S5, •% . S7 AND SQ - STOPCOCKS.
FIG.9.8.1. APPARATUS FOR THE DETERMINATION OF MOISTURE IN GASES
- 121 -
p re s su re developed by mois ture . B1 and B a re two bulbs of known JL Ci
volume into which moisture may be expanded to enhance the higher
limit of estimation. Another liquid nitrogen t r ap (6) aids in getting
the desired high vacuum with the help of the ro tary vacuum pump (8).
The entire apparatus is evacuated and liquid nitrogen
introduced into the cryogenic t rap (6). The argon coming from the
cylinder is metered by the venturi meter (2) and let out through T..
to the atmosphere. In order to condense the moisture from a known
volume of gas , S-, is closed, simultaneously opening S„ and S so
that the gas escapes out through T . The liquid nitrogen-acetone
s lu r ry is introduced in 3 and the moisture condensed for two mi
nutes . Subsequently S„ and S_ a r e closed while opening S 1 . The
argon remaining in the portion between S„ and S„ is pumped through
(4) by opening S„- The moisture is recondensed in 4 and then S„ o o
and S7 a re closed while opening S . . The t rap surrounding 4 is
removed and portion 4 warmed. The moisture is thus expanded in
the line and the p ressu re noted in the oil manometer. Fo r higher
mois ture contents of the gas , the bulbs B . and B a r e used for
expansion of the mois ture . Knowing the p res su re (P..) and volume
(V1) of mois ture , the moisture content can be calculated. The value
of p r e s su re (P.) and volume (V.) which the moisture would have if
it behaved ideally were obtained by the equation
P V 1 1 P.V. = - _
P o
Where P = saturated vapour p re s su re of mois ture . The amount
of mois ture is calculated from the equation;
- 122 -
K P , V.
(273 + t)
where t = system tempera ture
in milli l i t res
273 d oi l K = - ^ - x
76 cL, Hg.
where d = density. •
The blank of the experiment was evaluated by perform
ing the experiment without passing of argon. A reproducible value
of 4 mic ro l i t r e s was obtained for a condensation t ime of 2 minutes.
A set of experiments were done for the judicious se lec
tion of flow ra te s that can be employed for the experiment. Fo r
th i s , the gas was passed through the set up at various flow ra tes
and the mois ture estimated. A flow ra te between 420 and 500
ml /min . was found to give consistent r e su l t s . The flow ra te was
subsequently fixed at 450 ml /min , for al l the mois ture determina
tions.
The validity and accuracy of this experiment was ve
rified by using BaCl . 2H O as the standard source of mois ture . n
Barium chloride was taken in a react ion tube and heated at 200 C.
The standardisation experiments were found to yield satisfactory
resu l t s and the standard deviation observed was 8.02%.
REFERENCES
1. M . S . Kr'ishnan and V . B . Nagvenkar, Indian Journal of Techno
logy, J^2, 572 (1974).
2. D .A. Otterson, Anal. Chem., 33.450 (1961).
3. P . J . P . Chastagner, AEC R & D Report DP-766 Chemistry (1962).
- 123 -
10. REACTOR CONSTRUCTION
10. 1 Defect-Investigation Report on 80 mm Dia. IS-2062 Round (N. Sampath and G. Mallikarjun)
This investigation report pertains to an indigenous supply
of 80 mm dia. IS-2062 rounds. The mater ia l has been procured for
the various components required for the Special Flask, Fuel Charging
and Discharging F lasks , Transfer Blocks and Material and Personnel
Airlocks of FBTR Project . Since only a certification of guarantee for
the product was issued by the supplier in lieu of the mater ia l test
certif icates a detailed examination was undertaken at RRC.
As a first step, all the pieces were subjected to visual
examination and dimensional checks. Dimensional check was found
to be satisfactory. On visual examination of one of the 20 pieces,
incidentally earmarked for generating test samples for determining
the mechanical and chemical proper t ies , at one end of the round,
perceptible changes in the shades of the colour of the steel , probably
indicating difference in densit ies, were noticed. During the initial
stages of cutting of tensile tes t specimens, a severe case of slag ;
inclusion in the form of piping at the core of this round was r e
vealed. Figure 10 .1 .1 indicates the presence of slag inclusion
clearly.
Chemical analysis of (i) the slag region and (ii) the
base mater ia l , along with the IS: 2 062 requirements a re given in
Table 1 0 . 1 . 1 .
Hardness value for the surrounding s teel was found to
be 61 B Rockwell (103 BHN, 108 HV).
-124-
©
fe • ^ O ^ i -
FIG..10.1.1 SLAG INCLUSION IN THE FORM OF PIPING AT CORE
- 125 -
Results of Chemical Analysis
Elements
Carbon %
Sulphur %
Phosphorus %
Silicon %
Manganese %
Slag
0.40
-
0. 02 0
0.25
0.27
Bas e Material
0.13
0. 020
0. 037
0. 037
0.63
IS:2062 Spe-cification(l)
0.20
0. 055
0. 055
Not indicated
Not indicated
REFERENCE
1. Specification for Structural Steel (Fusion Welding Quality); IS: 2062-1969 (Indian Standards Institution, New Delhi -1970)
10.2 Calibration of a Pendulum Impact Testing Machine (N. Sampath and G. Mallikarjun)
The pendulum type impact testing machine at Central
Workshop has been calibrated as per the method IS: 3766
Dimensional and physical verification of the impact testing machine
and direct check by tes t on unhotched testing pieces were undertaken
as suggested in the method. With reference to "testing in a reference
machine" one of the impact testing machines available at BHEL
(Tiruchirapalli) , already calibrated as per ASTM E 23-66, was
taken as the reference machine. A plain carbon steel containing
0. 12%C, 0.024% S and 0.021% P was chosen as the test mater ia l
for calibration, Test pieces were heat t reated so as to have
"uniform proper t ies" as required in the standard. The normal isa
tion heat t reatment consisted of loading in a furnace at 650 C.
- 126 -
heating to 910 C, allowing for a soaking time of 30 minutes followed
by subsequent air cooling. The test pieces were of length 55 (±0.05)
mm; width 10 (±0.05) mm; for obtaining different absorbed energy
levels in the test pieces, three different thicknesses were chosen, 3,
' 5 and 7 mm (tolerance in thickness ± o. 01 mm). 30 test pieces of
each of the three thicknesses were prepared and heat t reated.
Five test specimens each, from the three different thick
nesses were tested in the"reference machine", with the sequential
choice of specimens str ict ly following the instructions in IS: 3766.
The resu l t s are shown in Table 1 0 . 2 . 1 , with the five resu l t s for each
thickness arranged in ' the increasing order of their magnitude (Tl,
T2 . . . . T5).
TABLE 10 .2 .1
Results of Absorbed Energy Values with Reference Machine
Result Test Piece Dimensions Designation 55 x 10 x 3mm 55 x 10 x 5mm 55 x 10 x 7mm
T l
T2
T3
T4
T5
2. 1 Kgfm
2. 2 Kgfm
2. 2 Kgfm
2. 2 Kgfm
2.2 Kgfm
6. 8 Kgfm
6. 8 Kgfm
6". 8 Kgfm
. 7. 0 Kgfm
7. 0 Kgfm
15. 8 Kgfm
15. 8 Kgfm
16. 0 Kgfm
16. 0 Kgfm
16.2 Kgfm
For all the three types of specimens, the absorbed energy
levels of approximately 2 Kgfm, 7 Kgfm and 16 Kgfm respectively, the
condition for uniform propert ies that T5 - Tl should be less than
5% of T l was satisfied. Five specimens of each of the three diffe
rent energy levels were then tested in the machine under calibration
and the resu l t s a re shown in Table 10. 2. 2.
- 127 -
Table 10 .2 .2
Results of Absorbed Energy Values with the Machine Under Calibration
Result Designa-nation 55 x 10 x 3mm
Test Piece Dimensions 55 x 10 x 5mm 55 x 10 x 7mm
Tl m
T2 m
T3 m
T4 m
T5 m
2. 3 Kgfm
2. 3 Kgfm
2. 3 Kgfm
2. 3 Kgfm
2. 3 Kgfm
7.1 Kgfm
7.1 Kgfm
7.1 Kgfm
7.1 Kgfm
7. 2 Kgfm
16.0 Kgfm
16.1 Kgfm
16.1 Kgfm
16.1 Kgfm
16.2 Kgfm
The repeatability is character ised by the difference between T5 m
and Tl m. If T5 m - Tl m does not exceed 10% of Tl m, the
repeatability of the machine at the graduation mark corresponding
to T3 is considered satisfactory. For all the three energy levels,
the machine was found to be all r ight with regard to repeatability.
The accuracy of the machine at the graduation. mark corresponding
to T3 was also found to be well within the IS requirement of not
more than 5% of T3.
T3 m - T3 T3
The accuracy expressed as % as per the formula
x 100 for the three energy levels a re as given below:
3 mm
5 mm
7 mm
2.3 - 2.2 " ~ 2 . 2
7.1 - 6.8 6. 8
x 100 = 4. 54 %
x 100 = 4.41 %
16.1 - 16.0 H
-—- x 100 = 0.625% 16. 0 The impact test machine at RRC Central Workshop thus
meets the calibration requirements of IS: 3766, upto the energy level
of 16 Kgfm.
-128 -
REFERENCE
1. Method for Calibration of Pendulum Impact Testing Machines for
Testing Steels",IS: 3766-1966 (Indian Standards Institution, New Delhi
1967)
- 129 -
11. MATERIALS SCIENCE
11.1 A Stochastic Model for Classical Bath Variables and its Influence on Line Shape Expressions (S. Dattagupta)
In the stochastic theory of line shape, it is recognised
that the radiating system (the nucleus in a Mossbauer experiment,
for example) is in a fluctuating environment. The fluctuations can
occur due to coupling of the nuclear spin with the lattice, coupling
between different nuclear moments through dipolar interactions,
t ime-varying quadrupolar interactions arising from the motion of
inters t i t ia ls or vacancies in the vicinity of the nucleus, etc.
Stochastic considerations were first applied to line shape
studies by Anderson and Kubo in an entirely c lass ical theory which
assumes that the frequencies of the radiating system undergo random
modulations , The lat ter a re assumed to be governed by a statu
tory Markov process . The same basic assumption about the under
lying stochastic processes in the environment (which is indeed the
major input in all subsequent developments of the theory) i s made
by Blume who has generalized the Anderson-Kubo model to cover
cases in which the quantum nature of the coupling t e rms becomes (2) very important .
A more complicated situation in the relaxation behaviour
of line shapes may ar i se in the case of hyperfine spectra in
paramagnetic system as can be determined by a Mossbauer or a
perturbed angular correlation (PAC) experiment. Here the surroun
dings do not interact directly with the nuclear spin but do so only,
with the ion ' that contains the nucleus. The nucleus feels the presence
- 130 -
of the surroundings via the magnetic hyperfine interaction with the ionic
spin. The interaction of the ionic spin with the surroundings may occur
through conduction electrons, coupling with lattic vibrations, coupling
with other ionic spins via dipolar or exchange interaction, etc. In such
cases the coupled nucleus-ion system is to be t reated exactly and quan
tum mechanically while the interaction between the ionic spin and its
surroundings may be taken into account by classical fluctuating fields.
The theory that we have worked out for handling the situation
mentioned above may be viewed as a straightforward generalization of (2)
the Blume model . In the lat ter it is only the nuclear spins which
are t reated quantum mechanically whereas their interactions with the
surroundings a re taken into consideration through effective fluctuating
fields. In the present case on the other hand, we have to t rea t a large
subsystem, namely, the coupled nucleus-ion system exactly and replace
the coupling between the ionic spins and their surroundings by stochastic
fields. The Laplace t ransform of the t ime development operator, from (3)
which line shape expressions are calculated, is obtained as
u(p) M p - i H * - i X Vj*F. -W) _ 1 (1) ° J J
where H* is the Liouville operator associated with the unperturbed
Hamiltonian H for the nucleus-ion system. The t e rm 2. V. F . o J j J 1
descr ibes the interaction between the ionic spin and its surround
ings and W is a matr ix whose elements give the probabilities of
transit ions per unit time in the surrounding bath system.
F r o m Eq. (1) the Mossbauer line shape can be expressed
as
F(p) = < A+["(u(p))avA3 > (2)
- 131 -
where A is a nuclear operator for the emission or absorption of
radiation, p = -iW+§- V with W the frequency of radiation and P
the natural line-width of the resonance. The symbol ^ . . . >
denotes a s tat is t ical average over the auantum states of the nuc
leus-ion system and ( . . . ) av, an average over the stochastic p ro
per t ies of the Hamiltonian.
In the case of PAC, on the other hand, the t ime- in te
grated directional correlation may be obtained as
G(p) = < A 1+ C ( u ( p ) ) a v ( A ^ A 2 ) ] A 1 > f ( 3 )
where p = f, T being the width of the intermediate level of
cascade, A., is the operator for the emission of the first &" ray
and A that for the second Jf ray . The time - differ e ntial cor
relation factor can be found from the inverse Laplace t ransform
of (3).
Using Eq. (1) we have derived line shape expressions
in different regimes of relaxation in which the relaxation r a t e s
a re smal ler than, comparable to, or larger than the unperturbed
frequencies of the radiating system. A detailed comparison of
the resu l t s with those of the existing theories has also been
made .
REFERENCES
1. P. W. Anderson, J. Phys. Soc. Japan 9,316 (1954);
R.Kubo, ibidj. 9, 935 (1954).
2. M. Blume, Phys. Rev. 174, 351 (1968).
3. S. Dattagupta, Phys. Rev. B.:L6, 158 (1977).
- .132 -
11 .2 Spin Re laxa t ion Spec t r a of ' 8 Qua r t e t (G. K. Shenoy*, B . D. Dunlap*, S. Dat tagupta and L . A s c h )
Cubic c r y s t a l f ields appl ied t o r a r e - e a r t h ions wi th odd
n u m b e r of 4f e l e c t r o n s r e s u l t in e l e c t r o n i c s t a t e s which a r e e i t he r
s i m p l e K r a m e r ' s doublets ( label led V or V^ o r q u a r t e t s ( P ) .
Recen t ly c o n s i d e r a b l e effort has been devoted to d i s c u s s i o n s of
p a r a m a g n e t i c r e l a x a t i o n s p e c t r a of 0—>" Z and •§•-*>>• 3/2 n u c l e a r
t r a n s i t i o n s in an ion with the T or T e l e c t r o n i c g round s t a t e s . 6 7
T h e s e s p e c t r a l s h a p e s a r e g r e a t l y s impl i f i ed by the fact tha t t he
sp in t r a n s i t i o n occurs , among the two l e v e l s of a K r a m e r ' s doublet
wi th an effective sp in S = \.
F o r the / _ level , the r e l a x a t i o n p r o b l e m i s s u b s t a n -o
t i a l l y m o r e complex . The s t a t e does not behave a s a s i m p l e S=3/2
s t a t e and the spin Hamil tonian i s a n i s o t r o p i c . In addi t ion the sp in
r e l a x a t i o n o c c u r s among four l e v e l s , the t r a n s i t i o n p robab i l i t i e s
b e i n g g o v e r n e d by the de ta i l s of the r e l a x a t i o n m a c h a n i s m .
We have p e r f o r m e d a n u m b e r of ca l cu la t ions for r e l a x a
t ion l ine s h a p e s for a T0 l eve l , c o n s i d e r i n g the deta i led f o r m s of (1) the i n t e r a c t i o n for v a r i o u s r e l a x a t i o n m e c h a n i s m s . The ion -ba th
i n t e r a c t i o n h a s been taken in two f o r m s . The f i r s t of these i s -?• —* ~ *
EL = o^.V h (t) , w h e r e V i s the v e c t o r o p e r a t o r equ i -
va l en t of T and h (t) i s a t i m e dependent m a g n e t i c field a r i s i n g 8
f r o m the ba th . Such an i n t e r a c t i o n i s app l icab le to r e l axa t ion due
t o s p i n - s p i n coupl ing, conduct ion e l e c t r o n coupl ing (Kor r inga m a c h a
n i s m ) o r s ing le phonon p r o c e s s e s v ia the Wa l l e r m e c h a n i s m . The
second f o r m of the ion-ba th i n t e r a c t i o n d e s c r i b e s the s p i n - l a t t i c e r e
l axa t ion due t o . modula t ion of the c r y s t a l l i n e f ield by phonons (Van
Vleck m e c h a n i s m ) . In addit ion, t h e . influence of . sma l l t e t r a g o n a l d i s -
t o r t i o n of t h e s e s p e c t r a l shapes a r e c o n s i d e r e d .
* Agronne Nat iona l L a b o r a t o r y , Agronne, I l l ino is , U . S . A .
+ T e c h n i c a l Un ive r s i t y of Munich, Ga rch ing , G e r m a n y .
- 133 -
Experimentally, we have measured the spin relaxation 1 fifi
spectra of states using the 80.6 k e V transition in Er ions in
the following systems:
1. Cubic compound Cs_NaErCl in which the spin-spin
coupling is dominant.
2. Cubic compound Cs„NaYCl„ containing a few thousand
ppm of Er impurities for which the spin phonon-coup
ling is relevant.
3. Pd metal containing less than 100 ppm of Er impurity
where the spin couples mainly to the conduction elec
t rons . We present a detailed theoretical discussion on
the analysis of these spectra
REFERENCE
1. G. K. Shenoy, B. D. Dunlap, S. Dattagupta and .L. Asch, Work
Reported at the International Conference on the Applications of
the Mossbauer Effect, Corfu (Gre ece), September, 1976;
See also Jour .de Phys. Colloq. C6, 3Ji. 8 5 (1 9 76).
11.3 Paramagnetic Spin Relaxation in Cs^ NaYbCl
(B.D. Dunlap*, G. K. Shenoy*, S. Dattagupta and L.Asch
The paramagnetic relaxation line shapes measured in
the cubic compound Cs0NaYbCl using the 84 .keV Mossbauer effect 170 2 6
of Yb d eviates considerably from that predicted by presently available theories . In this mater ia l the relaxation at low tempera-
3 + ture is dominated by dipole-dipoie coupling between the Yb ions.
* Agronne National Laboratory, Argonne, Illinois, U. S. A.
+ Technical University of Munich, Garching, Germany.
- 134 -
The theoretical discrepancy ar ises because the correlation frequency
associated with the spin bath driving the relaxation is comparable
to the hyperfine frequencies {l/tc & A where t^c is the spin
correlation time and A is the hyperfine coupling parameter) where
as all previous theories assume 1 /%.& "?> A. Theoretical expres
sions are obtained for the line shape removing this assumption by (2)
including the spin correlation functions in a more detailed way
The data is then satisfactorily described. Values are obtained for
the rms dipolar field in this material which are in agreement with
calculated values, and for the spin correlation time £ c . Implica
tions of this extension of the relaxation theories are discussed in (2)
regard to other systems
REFERENCES
1. -M.J. Clauser and M. Blume, Phys. Rev. B3, 538 (1971);
L . L . Hirst, J. Phys. Chem. Solids jU, 655 (1970).
2. B. D. Dunlap, G. K. Shenoy, S. Dattagupta and L. Asch, Paper
Presented at the International Conference on Magnetism,
Amsterdam, September 1976; See also Physica 86-88B, 1267
(1977).
11.4 A Stochastic Theory of Anelastic Creep, with Application to Snoek Relaxation (V. Balakrishnan, S. Dattagupta and G. Venkataraman)
Work reported earl ier on a stochastic theory of
creep has been corrected in certain essential respects and ex-
.(3)
(2) tended considerably . Linear response theory is applied to
the problem to obtain the fluctuation-dissipation (FD) theorem
for anelasticity, and to bring the treatment of mechanical res
ponse in line with the existing formalisms for dielectric and
magnetic response.
- 135 -
The Hamiltonian for a linear anelastic mater ia l of volume
V in the presence of an external s t ress is
H = HO - ve f^ct) <t> (i)
where H is the 'unperturbed' Hamiltonian and &. is the strain
variable. For an applied s t ress of frequency (£ , the observed
macroscopic strain is the average value
<£Ct)> =• R& CTCto) <Tt & ) ( 2 )
where J( 6& ) is the compliance. Applying linear response theroy
to the Hamiltonian in Eq. (1) yields (with & - V^Br )
relating the dynamic response J( fa ) to the equilibrium (zero
applied s tress) autocorrelation of the strain. The corresponding
creep function is found to be
These formulas may be written in t e r m s of quantity of experi
mental interest , the power spectrum
oo
st&) - 4 J ft os (At <£Co;ec^)>ei (5)
We obtain the important relation
- 136 -
which is the FD theorem for anelasticity. Together with the disper
sion relation for Re J( U> )> this determines J( Aj ) in t e rms of S( A3 ).
As in the case of Brownian motion, a complementary
stochastic basis may be given to the above theory by regarding the
general constitutive relation between the observed s t ress and anelastic
strain (which includes all network models) as the result of taking
ensemble averages on both sides of the basic stochastic equation.
e&&) + J di'^a-b')&t>) = ^ & + crcuuklct) m
E is the 'relaxed' modulus and 7](t-t ') is an anelastic 'memory'
function representing the dissipation or 'viscosity' in the system. It
can be related to the. autocorrelation of the random internal s t r ess
occuring in Eq„(7), yielding a generalized Nyquist theorem for anelas
ticity. Various moment relations for the power spectrum S( t^>) can be
established, connecting the parameters of phenomenological network
models to the underlying strain fluctuations in the system. The most
basic of these is the 'equipartition theorem' .
£ - ' ^ J Co) = nfrCtxO = f>V<<^>&± (8)
To verify the theorems proved, we consider Snoek re la -(4)
xation the creep caused by low concentration interstitial defects
in bee metals . In the simplest case , each defect forms an elastic
dipole of tetragonal symmetry that can take on three different
orientations. The autocorrelation of the strain may be calculated
from the equation
<-#9 ^Ct)\ - I tyJrt)£(o)\ri) Cnp^c^HC^Ie^JTn) (9) J- <XL7h '
- 137 -
where j n) is the stochastic state corresponding to the orientation
n(=l ,2 ,3) ; pn = 1/3 is the equilibrium Boltzmann factor for the state
I eq n); and (n p (t) m) is the element of the probability matrix
describing the evolution of the system from the state jn) at t = 0 to
the state ]m) at t ime t . Assuming that the re-orientation is a gq
stochastic process of the stationary Markov type, we have P (t) = gq gq
exp (W ^ ) , where W is the transition matrix that involves the
basic reorientation frequency ")> . Explicit calculation yields
«jrt*> - ij&y^a.-wV-e ) do)
the creep function corresponding to a Voigt element with a spring of
modulus
£ = Q/tzpVc1 £A,-A*.; J
and a dashpot of viscosity -77 ~
Here C is the molefraction of interstitial defects, and 7^\ , A ^ ,
A3 = A _ are the components of the elastic dipole s t ra in tensor in
its principal axis system.
Extensions of the theory to cover defect correlat ions,
non-linear response, irradiation creep , etc . a re under investigation.
On the experimental side, too, the possibility of studying strain
fluctuations via the monitoring of the concomitant resist ivi ty fluctua
tions by noise analysis techniques is being examined.
REFERENCES
1. V. Balakrishnan and G. Venkataraman, Activity Report 1975,
RRC-19, (1977) p . l l l .
- 138 -
2. V. Balakrishnan, S. Dattagupta and G. Venkataraman, Nucl.
Phys. & Solid State Phys. (India) 19C, 189 (1976); Phil . Mag,
J37, 68 (1976).
3 . R. Kubo, Rep. P rogr . Phys. J29, 255 (1966).
4 . A . S . Nowick and B .S . Ber ry , Anelastic Relaxation in Crystalline
Solids (Academic, New York, 1972).
11.5 A Solvable Model for Clustering of Quenched-in Vacancies (G. Ananthakr ishna)
When a mater ia l is quenched, it is observed that a variety
of extended defects a re formed mainly due to the supersaturation of
vacancies. The object of this work is to build a model which takes a
microscopic point of view and which can describe the clustering of
vacancies adequately. For simplicity, we specialize to the case of (1,2)
faulted hexagonal loops in quenched aluminium ' and to the forma-(3) tion of stacking-fault tetrahedra in quenched gold.
The equation for the ra te of change in the concentra
tion of clusters with various sizes a re written down with the assump
tion that only single units a re mobile (single units may refer to
single vacancies or divacancies whichever is more mobile). Let
N 1 ( N_, . . . . . , N be the concentration of 1- , 2—, . . . . , n - unit 1 2 n
clus ters . Then
d-fc z. *•
- 139
with
and
We shall assume that X-\C^i^~^ " ^xCT) , since (as we will
show later) this quantity is related to the experimentally measurable
quantities and therefore can be regarded as a parameter to be de-
termined. Define «*•£*/*) for / a | ^ ' by 7, fair) * Z tin ^ a.
. Then,
It is possible to decouple Eq.(5) and E q . ( l ) , then
Thus , the concentration of single vacancies approached itB a asymp
totic value very rapidly in about a fraction of a second. The nuclea-_2
tion time is of the order of 10 sec . for aluminium quenched from
600 C to lo C. This is in good agreement with the resul ts of
Kiri tani . Using this asymptotic value of N and ignoring the last
t e r m , (since N_ is one of infinitely many complexes) we can solve
for 2£2v£} with the initial condition Xi^/O) = O • Invert
ing %C%/t) we obtain
(j-W)*- L n, d-frO-bfl/
- 140 -
where h- Ho/CHc+%^) and (j>~ z*p (- ^ z* ^/ >Va •+•*• *)
With the interpretation that n is measured from the position of the
peak 7[0 W e find that %^ i s related to <7l > and 7lo .
Thus it can be regarded as a parameter . The resul ts on average (1*3) density for the case of quenched aluminium and gold ' is shown
in Table 1 1 . 5 . 1 . It is seen that the agreement is good. The cha
racter is t ic t ime for the formation of large clusters is
*£•• <*•>.. - = - 2 — £ f . which is of the order of a few hours for gold ^ ^ o o
quenched from 980 C to 40 C.
TABLE 1 1 . 5 . 1 .
- .
An
Al
Al
The Data Used
T Q
in
°C
980
600
580
for
T A in
°C
40
10
40
C . - •
1
omputing the Total
3
5
.2
L 2
N % o . . A-
x 10"4 . 410
x 10~5 300
x 10~4 600
Density of Clusters
L o in A°
380
270
570
Total Density
Expt. per Theory per 3 3
cm cm
3.2 x 10 1 7 2.2 x 10 1 6
3.0 x 10 9.0 x 10 1 ft 1 ^
3.0 x 10 2.0 x 10
REFERENCES • • v
1. M. Kir i tani , , J . Phys. Soc. Japan, Jj5, 95 (1973).
2. R.J . Di Melfi and 'R.W. Siegel, Ph i l , Mag. , _24, 188 (1971).
3 . K . C . Ja in and'R.W'. Siegel, Phi l , Mag. , :26, 637 (1972).
-141-
11. 6 A Consistent Linearized Green Function Theory of the S=f Heisenberg Ferromagnet (R. Balakrishnan and V. Balakrishnan)
In an ear l ier paper , the general s tructure of linearized
Green function theories (LGT) of the Heisenberg ferromagnet was ana
lyzed, with part icular emphasis on the spin wave energy renormaliza-(2) tion factor. Spectral theorem and rigorous low temperature resul ts
were used to derive certain necessary conditions on this factor. The
special difficulties that occur in the case S = i were brought out, and
the impossibility of obtaining the correct low T resul ts for both the
spontaneous magnitization (T and the specific heat 7 in a con
ventional first order theory was eatablished.
A completely consistent LGT for S = \ has been derived (3)
now , taking into account all the constraints listed in Ref. 1, Most
important among these is the full incorporation of the special identi
ties satisfied by the spin operators in the case S = \ namely, the anti-
commutation relation between the spin-flip operators and the vanish
ing of the squares of these opera tors , over and above the usual
equal-time commutation relat ions. These identities (which represent
quantum mechanical effects) a re quadratic in the spin opera tors , and
are therefore crucial in deciding the form of a linearized theory,
especially at low tempera tures . The next condition to be satisfied
is the conservation of at least the zeroth and first moments of the
basic spectral function, ensuring -the correct determination of the
total magnetization, and the energy of the system. Finally it is ne
cessary to retain all possible two-spin correlations in the process
of decoupling higher order Green functions. A careful study scru
tiny of the linearization process leads to a derivation of the optimal
LGT that does not have any of the inconsistencies of ear l ier theo
r i e s (which ar i se from the neglect of one or more of the conditions
listed above). The key role played by the longitudinal spin-spin
- 142 -
correlation is elucidated, and a unique expression for this quantity is
determined, from which various l imits and special cases a re recover
ed correct ly .
The 'no-go' theorem, for 6~~ and ~Y in conventional
first order theories mentioned in the beginning is circumvented by
the fact that the basic Green function G(k,E) in our LGT satisfies an
integral equation in momentun space , instead of the usual algebraic
one. This implies the existence of a dispersive part in the Green
function in the complex energy plane, in addition to the usual pole
t e rm . The evaluation of the discontinuity of the Green function across
the r e a l axis in the E-plant enables us to compute 6~, '"Y etc.
via the spectral relat ions. We obtain, for the first t ime in an LGT,
low-T asymptotic se r i e s for these quantities that agree with the r i -
4
gorous resu l t s all the way upto 0(T ), when the effects of the dyna
mical interaction between spin waves start manifesting themselves .
The physical reason for this high degree of accuracy is as follows:
the pole t e rm in G(k,E) in an LGT represents a (renormalized) spin
wave excitation. In our theory, this t e rm is modulated by the dis
persive par t , which is a continuous superposition of renormalized
spin wave t e r m s representing the contribution of (interacting) many-
spin-wave s ta tes . This explains why, even at the level of an LGT,
We have been able to include the effect of the relevant part of the
spin wave interaction in a much better manner than has been done
ear l ie r .
With the low T region taken care of, we proceed to the
other limit of the ferromagnetic region (T —5* T )* since a
Green function theory is meant to provide an interpolation over the
entire tempera ture range concerned. We show first that the well (4)
known random phase approximation (RPA) is the only thermo-
dynamically consistent LGT in the limit T -^» T (or 6~- >- 0),
- 143 -
providing a formal reason why this approximation yields numerically
good resu l t s near T • We show also that our LGT derived for
T < T does go over into the RPA limit as T-^T , the solution to c c
the integral equation collapsing to the spin wave pole t e r m of the
RPA, with the energy renormalizat ion factor 2 C
REFERENCES
1. V. Balakrishnan, Phys . Rev. Bll , 256 (1975).
2. F . J . Dyson, Phys . Rev. _102 , 1217, 1230 (1956).
3 . R. Balakrishnan and V. Balakrishnan, Phys . Rev. B ( to be
published).
4 . S.V. Tyablikov, Ukr. Mat. Zh. JL1, 287 (1959); F . Engler t ,
Phys . Rev. Lett . J5 , 102 (1960).
11.7 Tensor Product Composition of Algebras in Bose and F e r m i Canonical Fo rma l i sm (Debendranath Sahoo)
In this work, an axiomatic framework has been provided
for the understanding of the foundation of the canonical (Hamiltonian)
formalism of c lass ical and quantum mechanics. It is assumed that
algebra is the primitive s t ruc ture , and auxiliary s t ruc tures like to
pology a re to be imposed la ter . Such a view originated with the
pioneering work of Jordon, Von Neumann and Wigner
The algebras of physical variables of both c lass ica l and
quantum mechanical systems involve two products interrelated to each
other. F o r example, if f, g, h a re classical var iab les , the two
products a r e the ordinary multiplication ' . ' (commutative and associative
and the Poisson bracket (anticommutative and non-associative) operation
v 3" and they are related by the derivation law: i
- 144 -
The Poisson bracket also satisfies the Jacobi identity:
L fi { $ >LH + Cyclic t e r m s = 0,
and is a Lie product. In quantum mechanics, the products ana
logous to the ' . ' is the anticommutator ( a commutative, but non-
associative Jordan product) and that analogous to £ . \ is the com
mutator (again, a Lie product).
(2 3) It was shown ear l ier ' that if one s t a r t s with a
two-product algebra such that nothing is assumed about one product "
and the other is assumed to be a Lie product which is also a de r i
vation with respec t t o ' t he former , and if one postulates that the
tensor product of two such algebras is another one of the same type,
then the complete (algebraic) s t ructure of the canonical formalism
of both c lass ical and quantum mechanics can be derived.
(4) In the present approach , two additional s t ruc tu res -
namely, a gradation s t ructure and a factor of commutation a re in
cluded. The two -product algebra is assumed to be a regularly
graded algebra with positive integers (including zero) as the group
of the degrees , and the factor of commutation is a bilinear mapping
of the group of the degrees to the set | . +1 , - 1 \ . Then the
same axiom is shown to lead to the complete algebraic s t ructure
pertaining to both Bose and F e r m i system in c lass ical and quantum
"mechanics.
- 145 -
REFERENCES
1. P . Jordan, J. Von Neumann and E. Wigner, Ann. Math. 35,
29 (1934).
2. D. Sahoo, Doctoral dissertat ion, Yeshiva University, New
York (1972).
3. E . Grigin and A. Pe te r sen , Algebraic Implications of Com-
posability of Physical Systems, Yeshiva University Prepr in t (1976)
4. D . Sahoo, Pramana , J3 , 545 (1977).
11. 8 An Apparatus for the Measurement of the Angular Correlation of Position Annihilation Radiations (B. Viswanathan, "V. Anandkumar, C.S . Sundar, S..K. Sarkar and K . P . Gopinathan)
A 6. 6 me t r e long apparatus for the measurement of the
two-photon angular correlat ion of annihilation radiations of positrons
in mater ia ls has been designed and built. The sample under study is
kept shielded from the detec tors . The posi t rons, after being stopped
and thermal ised , get annihilated with electrons in the mater ia l . The
two 511 keV annihilation photons a re detected by scintillation Coun
ters : kept at 180 with each other. Because of the finite momentum
of the electron with which the positron annihilates the angle between
the two photons deviate from 180 by a small angle, d 0 = p /mc , z
where p is the component of the electron momentum in the direction
perpendicular to the plane of the detectors- The y component of
the momentum, p , is averaged out by using sufficiently long detec
to r s . Thus the coincidence count ra te of the two 511 keV photons
as a function of the angle between the detectros gives information on
the distribution of the z-component of the momentum of electrons in
the mater ia l .
- 146 -
The mechanical system consists of two a rms each 3.3
me t r e s long and made of aluminium channels, a source chamber , a
pair of coarse sl i ts near the source chamber , a pair of adjustable
fine sli ts near the de tec tors , and two detec tors , each enclosed in a
shield having a 6 m m x 310 mm slit for the entry of the gamma
rays (Figure 11.8.1A). The source chamber is provided with a r range
ments for placing the sample in the view of the detectors while keeping
the positron source shielded from the detectors with 6 cm lead en
closed diameter Nal (Tl) c rys ta l coupled to an RCA 8575 photomulti-
pl ier . By. adjusting the width of the fine sl i ts the angular resolu
tion can be chosen to be upto 0.2 mil l i radians. One detector is kept
fixed and the second one movable in the-vertical direction by small
angles along an axis passing through the sample . The weight of the
movable a r m along with the sl i ts and the detector housing is com
pensated for by a counter weight a ssembly. The ver t ical .motion
is effected by a counter weight assembly. The detector , the s l i ts
and the sample have been a r r a n ^ ' in a horizontal plar^d and the
alignment tested by use of a l a s e r .
A fast-slow coincidence system having a resolving
t ime of 60 nsec has been employed to record coincidence counts
due to the photopeaks of the 511 keV annihilation photons. Angular
distribution of annihilation radiation from a pure aluminium sample (1,2)
has been measured withthe present set up. The well-known
parabolic correlat ion in the infinitely long detector geometry expected .','
for annihilation with free electrons in a metal has been observed and
is show in Fig . 11. 8. I B .
REFERENCES
1. A . T . Steward I n , Posi t ron Annihilation, Edited by A. Tl Steward
and !L.O. Roelling, (Academic P r e s s , New York 1967), p . 17.
2. I. Ya. Dekhtyar, Phys. Repor ts , 9 , 243 (1974).
- 147 -
4 2 0 2 U
ANGLE (mHli radians) e a 12
2MK) 3420.
FIG.11.8.1 «. SCHEMATIC DIAGRAM OF THE POSITRON ANNIHILATION
ANGULAR CORRELATION APPARATUS.
1. SAMPLE 2. SOURCE HOLDER 3. COARSE SLITS
4. FINE SLITS 5. DETECTOR SHIELDS 6.DRIVING SCREW
7. COUNTER WEIGHT ASSEMBLY.
B. A TYPICAL ANGULAR CORRELATION CURVE OF ANNIHILATIONS
IN Al.
- 148 -
11. 9 A set up for Measurement of Life-t imes of Positrons in Metals (C.S. Sundar, S.K. Sarkar , B.Viswanathan and K.P.Gopinathan)
A system, for measuring sub-nanosecond life t imes of 22
positrons in metals has been set up. The positron source (Na )
is sandwiched between the two thin discs of the mater ia l under study.
The t ime delay between the 1278 keV prompt gamma ray from the
22
decay of Na and one of the 511 keV photons produced by the annihila
tion of positrons in the sample is measured. The gamma rays a re
detected by two scintillation counters each consisting of a 2.5 cm diam.
x 2 .5 cm thick NE 111 plastic scintillator coupled to a Phillips Xp-
2230 photomultiplier, the anode of which is operated at approximately
3 kV. The anode pulse from each detector is shaped by a fast d i s c r i - '
minator . The output of the two fast d iscr iminators from the START
and STOP inputs of a t ime-to-pulse-height conver ter . A l inear out
put is taken from the 9th dynode of the photomultiplier and suitably
amplified. Pulse height windows near the compton edges of the 1278
keV and the 511 keV gamma rays respectively a r e selected by use of
single channel pulse-height ana lyse rs . A slow coincidence and l inear
gate unit is used to select those output pulses from the t ime-to-pulse
height convertere which a re in coincidence with the selected gates in
the tv/o channels. The output of the l i nea r gate is analyzed by a multi
channel analyser . fin
The prompt t ime distribution was measured using a Co
source . This showed a half-width of 500' psec and a slope of 70 psec .
Typical t ime distributions of positrons annihilating in pure aluminium
and copper samples a r e shown in P ig . 11 .9 .1 along with the prompt
curve.
The set up is being used for the study of defects produced
in metals by irradiation and ;quenching.
1000
t CO
3 o o 100 r
(A) ALUMINIUM
10
(B) COPPER
230 p sec
70psec
215psec
70psec
750 • M S
CO
• •• ••
750
CHANNEL NUMBER Fig. 11 .9 .1 . Observed life-time graphs for positrons 'in(a) Aluminium and (b) Copper along with prompt
spectra (shown slightly displaced in both directions for clarity). Values given are slopes of respective curves uncorrected for instrumental resolution.
- 150 -
11.10 A Cryogenic Irradiation Facil i ty for On-line Positron Annihilation Experiments (R.V. Nandedkar, B. Viswanathan and K . P . Gopinathan)
•,. A liquid nitrogen irradiation facility to perform on-line
positron annihilation and resis t ivi ty measurements on mate r ia l s i r
radiated with energetic charged par t ic les from Van de-Graaff acce
lera tor or cyclotron has been designed and fabricated. The entire
set up, except the detector enclosures , is of welded stainless steel
construction.
The set up consists of two par t s : an irradiat ion chamber ,
and a liquid nitrogen cryostat . The irradiation chamber is in the
form t>f a cylinder with six ports each at an angle of 60 with the
"adjacent one. Two por ts provide the axis for the passage of the
accelera tor beam. Two other ports at an angle of + 60 to this axis
provide the housing for the gamma detec tors . The detector housing
consists of an aluminium cup recessed into the irradiation chamber
and welded to a flange. It is vacuum coupled to the .chamber. The
remaining two ports have been provided for a vacuum gauge and a
viewing por t . The chamber has been provided with a top and bottom
flange to connect the cryostat and the vacuum system respect ively.
The liquid nitrogen cryostat consists of a two-litre«- ./.
cylindrical stainless steel vesse l suspended by two thin walled stain
less steel, tubes from a tdp flange. A copper cold finger is welded
to the lower end of the .vessel . The sample assembly is fixed to an
extension rod and screwed on to the cold finger. It is capable of
ver t ical t ranslat ion to adjust the sample in the path of the beam. The
liquid nitrogen vesse l is surrounded by an outer enclosure of chro
mium plated b r a s s . The annular space between the liquid notrogen
vessel and the outer tube is evacuated for necessary thermal insula-
- 151 -
F I G . 1 1 . 1 0 . 1 CUT-AUAY VIEW OF THE LIQUID'NITROGEN IRRADIATION FACILITY.
1.SAMPLE 2.COLO riNGER. 3.DETECTOR A.ALUMINIUM \\ CUP: 5 .L IQUID NITROHEN; 6.SUSPENSI0N TUBES
7.TOP FLP.NGES; G.CLASS-TO-METAL SEftL; .' ' ' 9 . SJFF4JSI0N PUMOj 10 . BEAM DIRECTION
- 152 -
tion. The thermocouple leads and the heater leads e tc . from the
sample a re taken out from the top flange of the chamber through
a g lass- to-meta l vacuum seal . Figure 11.10.1 gives the cut-away
view of the facility. The entire system has been tested for leaks
using a helium leak detector. Under operating conditions a vacuum -5 better than 10 t o r r has been obtained,, The tempera ture at the cold
finger measured after pouring liquid nitrogen in the vesse l was 85 K
and was found to remain constant to_+- J C for several hours . By
providing a heater wound around the sample holder and using a t e m
pera ture control ler , the sample can be kept at any temperature bet
ween liquid nitrogen tempera ture and room temperature ' and room
tempera ture to an accuracy of +1 C,
11.11 A Cryostat for Measurement of Transit ion Tempera tures of of Superconducting Specimens (Y. Hariharan and T . S . Radhakrishnan)
Many cryostats have been reported in l i tera ture which
enable one to achieve tempera ture variation over that of a boiling
cryogen by providing a controlled amount of heat to the specimen is
achieved in most cases ei ther by placing the specimen in an evacuated
chamber or by placing it at the end of a cold finger with a heater in
terrupting the refrigration to the specimen. The former involves cold
vacuum seals result ing in cumbersome procedure for changing samples .
In the la t ter it is difficult to meet the two requi rements , namely going
down to lowest temperatures and varying the tempera ture with r e l a
tively low boil off of the refr igerant , simultaneously. In the cryostat
described below the refrigeration provided by the vapour above a liquid
helium bath is made use of, in obtaining tempera tures higher than that
of the normal boiling point of the liquid.
- 153 -
The cryostat, shown in Fig. 11 .11 .1 , consists of a copper
block (4) to which the sample under study, a germanium res is tance
thermometer ," a sensor in the form of ;a carbon res i s to r , and a 10 Ohm
constant heater a re thermally attached. This copper block is shielded
by another copper can (6) and is suspended by means of a thin walled
stainless s teel tube (2) from the top (1) of the cryostat . A thin walled
s teel tube, (not shown in figure which can be attached to the top,
surrounds the assembly and enters the helium spare through a Wilson
seal in the top flange of the dewar containing liquid helium. Electr ical
wires can be taken out through the feed through (6). The stainless
s teel tube and hence the sample can be placed at any height above that
of the boiling liquid. This along with a controlled amount of heat
facilitates one to obtain any temperature between 4.2 K and 25 K.
Unlike other designs changing of samples can be effected very easily
in this setup and there is no need to warm the dewar to room tempe
ra tu re .
This cryostat is at present being used to measure t r ans i
tion temperature of superconductors. The transit ion is measured
res is t ively using the standard four probe technique. The cryostat is
being tes ted for temperature stability, with an electronic temperature
controller . Stable tempera tures in the region 4.2 - 18 K have been
obtained for periods in excess of 45 minutes. The temperature stability
was bet ter than 25 mK in this period. Fur ther , the tempera ture
achieved was found to be independent of the liquid level in the dewar
upto a tested range of 10 cms, provided the refrigeration available
was enough to cool the sample holder to the required tempera ture .
REFERENCE
1, G. K. White, Experimental Techniques at Low Temperatures
(Oxford University P r e s s , London, 1968).
- 154 -
TIG. 11.1.1.1 CRYOSTAT FOR MEASURING SUPERCONDUCTING TRANSITION TEMPERATURE. NUMBERS REFER TO PARTS WHICH ARE EXPLAINED IN THE TEXT.
- 155 -
11.12 Study of Bridgman Anvil Apparatus for Measurement of Elect r ica l Resistance at High P re s su re s (Rita Kapoor, V. Sankara Sastry and K. Govinda Rajan)
A Bridgman anvil type high p ressu re apparatus has been
designed and built for studying electr ical behaviour of mater ia ls to
100 kbar. The apparatus consists of a pair of tapered pistons between
which the sample under study i s enclosed in a gasket (Fig. 11.12.1) .
The pistons are aligned, mounted in a high-tonnage press ,and subjected
to uniaxial compression. The uniaxial s t r e s s i s converted to quas i -
hydro-stat ic p ressu re on the sample by enclosing the sample in a soft
matr ix like si lver chloride steati te etc. before loading it into the
gasket. Elec t r ica l leads from the sample can be taken either through
the anvils, or through the gasket. P r e s s u r e in the sample region is
measured by noting the loads at which the well-known discontinuities
in the e lectr ical res is tance of bismuth, tel lurium, thallium etc. occur.
Tungsten carbide was chosen as the anvil mater ia l , and
the taper in the anvil immediately below the working face aids the
fanning out of the s t r e s s immediately below the working face, thereby
making it possible to generate p re s su re 2-3 t imes the compressive
strength of the carbide. It is customary to push-fit a binding r ing
on to the carbide for l a te ra l support . But a simple calculation of
the s t r e s s e s (hoop s t r e s ses ) shows that there is no need for the
binding r ings , upto 100 kbar, and the apparatus reported here has
been used without binding rings repeatedly upto 100 kbar . The
working face of the anvil should, however, be work-hardened before
subjecting the anvil repeatedly to such high p r e s s u r e s .
Reproducibility of p ressu re behaviour in this apparatus
depends essentially on the reproducibility of the s t r e s s system
from run to run. Either one could put two samples - the tes t
sample and the calibrant - in one cell and avoid the problem, or
- 156 -
LOADj
l ^ - v M ^ k ^ v M ^ q
LOADJjj
KEITHLEY U 8
NANOVOLT METER
ANVILS
•SCHEMATIC DIAGRAM OF ABRIDGMAN ANVIL APPARATUS
FIG.-IT. 12.1..
- 157 -
(2) systematically factors which affect the reproducibility . The la t te r
approach was adopted, and al l parameters relevant to the setup in
the order of importance were identified. They a re (i) the initial ga s
ket thickness (hi), (ii) the ra t io of the gasket o.d. to i .d . (K),(iii)
the gasket mater ia l and i ts uniformity, (iv) the nature of the sample
assembly loaded in the gasket , (v) the degree of under-loading,and
overloading between the gasket and sample assembly and (vi) the
taper angle in the anvil. In this work pyrophyllite was used as the
gasket mate r ia l .
F igure 11.12.2 shows the variation of final gasket
thickness h„ as a function of the initial gasket thickness h. for a
given load, from which it is c lear that for h. > h , h„== h and ° i. c i c
for h. <£h , h = h . . Also from the experiments on p r e s su re cal i
brat ion, it was found that for a given highest p r e s su re at the
centre of the gasket (for example, the Bi I-II t ransit ion p r e s s u r e ,
25.4 kbar) the rat io of this p r e s s u r e to the average p re s su re
between the anvil faces is a function of the initial gasket thickness ,
and thus estimating the p r e s s u r e from simply load/area would .'lead
to erroneous r e su l t s . In fact, the ra t io of the actual p re s su re to
the average p r e s su re ( load/area) , called the degree of p r e s su re
concentration (d.p.c) has a behaviour shown in Fig . 11.)2. 2. It is
found that a d . p . c . of, sometimes as high a s , 8 may be observed.
F r o m these considerat ions, the cor rec t procedure for sample a s
sembly was found to be as follows:
(a) It is clear that initial gasket thicknesses in the region
in which do p . c. is a steep function have to be avoided,
because in this region (d(d.p. c .) /dh.)P which is a
measure of reproducibil i ty, is l a rge . Thus only those
thicknesses for which (d(d.p. c . ) /dh.) = 0 should be
employed. This r e s t r i c t s the h. to either very smal l
values or to values > h . The la t ter region is
•*- FINAL GASKET THICKNESS, hf (mil).
a
to
o - I
n Ul tn <r a> i ' i
n o z l"i m 2 -H X *» -< t - *
o J:
-*1 a X
• D
-< 33 a T> I -< r i -
o •n
- i X n -n • - 4
B! f t~ O
:=> </) ZK. m -< - i
1-4
n 7Z Z m in (0 3> Z o
X n o m r> m m
t
>
> CO
m
o
m CO
o
NJ O
CO
o
.c-
• o CL.
— ifi w
_3"_?"
1
PY
RO
P H
YLL
=5 m
O
1
V •
•
1
|VO
o 1
° \
1 1
CO
o 1
1
,
1 1
1 1 tNJ CO cn a>
DEGREE OF PRESSURE CONCENTRATION (dpc)
- 891 -
- 159 -
preferred because only in this region the d .p . c . i s l a rge .
(b) Having chosen the initial thickness as somewhat l a rge r
than h , the value of K is next to be fixed. Any value c of K above 6 was found to be satisfactory and was used.
(c) The total thickness of the sample assembly must be
slightly smal ler than the initial thickness of the gasketo
That is , the re must be some underloading. This is to
prevent distortion of the sample assembly during the run.
In fact, if the assembly is done well, the sample can be
re t r ieved intact after a p ressu re run.
(d) For prolonging the life of the anvil it is necessary
to work-harden the face of the anvil.
REFERENCES
1. H. G. Dr ickamer , Modern Very High P r e s s u r e Techniques
(Butterworths, London, 1962).
2. M.Wakatsuki, K . I . Ichnose and T.Aoki , Japan J»Appl. Phys .
JL1, 578 (1972).
11.13 Supersaturation Crystal Growth (R.Krishnaswamy and V. Rajalakshmi)
The supersaturat ion method of c rys ta l growth equip
ment, which was in fabrication stages was completed. It has (a) a
slow cooling facility (1 C/2h - 1 C / l2h) , (b) an accurate tempera
tu re control (+ 0.1 C), (c) a constant t ime periodic s t i r r e r r e v e r
sal to prevent inclusions , (d) a hermetic sealing to prevent un
controlled concentration gradients , (e) a vibration free arrangement
and (g) a fully automatic operation. It has two ro tary c rys t a l l i ze r s ,
- 160 -
for low speed and medium speed . The design, mater ia ls and fabrica
tion w e r e al l indigenous. Tes t runs for 160-200 h r s continuous were
satisfactory. The automated ro tary crys ta l l izer is in routine opera
tion now and is shown in F ig . 1 1 . 1 3 . 1 . This method is used for c ry
stals with a solubility - tempera ture gradient of - 0 .5g /(lOOg C)
of solvent, and with, no phase change during cooling.
Crystals of I ^ S O ^ l ^ O ^ ^ H ^ K ^ O ^ r ^ S O ^ ^ H ^ ,
Fe S04(NH ) SO 24H O and NaNO were grown using the above
method. A maximum dimension of 40 mm was obtained. The mixed
crys ta l of Agl, KI and (NH4>2S04 ,MnS04 is under p rocess .
REFERENCE
I . G. Petov, Ed. Growing Crystals from Solution, (Consultants
Bureau, New York, 1969).
I I . 14 Br idgman Crystal Growth (R.Krishnaswamy and V.Rajalakshmi)
A Bridgman furnace, using the ver t ical freezing techni
que, for growing crys ta ls with a melting point ^ 1050 C, which
melt congruently and which do not have high- vapor p re s su re at the
melting point has been rebuil t . The r a t e of lowering was kept va r ia
ble between 1-10 m m / h r , since the ra te of lowering to be adopted
is dependent on the nature of the c rys ta l , metal l ic , semimetal l ic ,
or non-metal l ic . A controlled tempera ture gradient of accuracy
+ 0 .5%, lead to a supercooling at the t ip of the crucible initiated
the growth of c rys ta l s . The gradient has to be optimised depending
on the nature of the c rys ta l , thermal conductivity, heat of fusion
etc .
- 1 6 1 -
UJ N
> -Q: o > -
< t— o cr o LLI
o I— Z> <
en
O
- 162 -
Bisumth crys ta ls 15 mm dia x 40 mm were grown suc
cessfully. Polishing and etching procedures were standarized. Zinc
c rys ta l s also were grown and a r e being analyzed by x - r a y and metal-
lographic methods.
11.15 Variable Speed Zone Refiner TR. Kr ishnaswamy)
The multipass ref iner , with 3 hea t e r s , a variable speed
motor of 0.4 ~ 3 rpm and a constant speed r eve r sa l motor at 20
rpm with automatic operation was completed. It incorporates a new
method of automation with a high torque constant speed motor con
trolled by a silicon rect i f ier . The entire refiner and accessor i e s ,
including the automation were indigenously designed, fabricated and
assembled. Tr ia l runs were satisfactory for temperature profile,
heater performance and smooth mechanical operation for 8 h r s of
continuous operation. Tftie equipment" is shown in Fig . 1 1 . 1 5 . 1 . The
zone leveller which uses the same mechanical assembly, is in
design s tages . Fo r a normal freezing
C = K C ( l - g ) K _ 1
o
where K is C /C.. (concentration of the impurity in solid/liquid
phase) , g is the fraction solidified, C is the initial concentra
tion, and C is the final concentration in the solid phase.
REFERENCE
1. W.G. Pfann, Zone Melting, (John Wiley, New York, 1966).
-163-
*Msg3ttL,-i-ii 8 1
m\
t-*Hi's
*****j "YO'jcinc;'
cr LL!
U_ ai cr LU O M
Q LU UJ OL CO
UJ
DC <
LO
O LL
- 164 -
11.16 Design and Fabrication of Oil Seals for a High Tonnage P r e s s (V.Anandkumar, K.Govinda Rajan and S.Aravamudhan*)
A shor t -s t roke high-tonnage p ress was designed and built.
The oil sea ls in the r ams required careful designing and precision
machining. 0-rings backed with teflon rings were found to serve the
purpose well , and were tested upto 25,000 ps i . F igure 11.16.1
gives the details of the seals along with their dimensions. .
Four aspects had to be considered while designing the
sea l s , namely, compatibility of the seal mater ia l with the environ
ment, wear of the seal due to abrasion, clearance between the sea
ling sur faces , and finally the relat ive mis-orientat ion of the seal
both during assembly and operation. 0-r ings were chosen because
they a r e the most common type of squeeze-packing used in static
as well as dynamic conditions, a r e inexpensive, seal in both d i rec
tions and a r e suitable for reciprocat ing, oscillating and slow-rotary
motions. The sealing action is both due to the diametra l squeeze
caused during installation, and the deformation caused by the con
fining liquid. Normal squeeze required to seal 1500 psi is about
10% of d iameter . It was thought that a higher squeeze would sea l
larger p r e s s u r e s , even though this would resul t in increased fr ic
tion and wear . Since both the s t roke and speed are very low for
our p r e s s , it was decided to use 15% initial compression in the
design. The next parameter to decide was the clearance gap
between the sealing member s . It was realized that an optimum
value had to be chosen because , while a la rge gap simplifies the
assembly of p a r t s , it would also resu l t in easy and excessive
extrusion of the sea l through the gap under high p r e s s u r e , where
as a smal l gap would make the assembly of pa r t s very difficult.
In the present design, two teflon r ings were used to support the
0-r ing, but also locked it in place, thus preventing eny m i s -
orientation by rolling. ^Engineering Services Group, Reactor Research Centre
- 165 -
O.R c.s,p 5.33mm
N 6 • • •..;•-•.
I . D .'•:•
88 mm
HIGH PRESSURE .SEAL
Fig. 11.16. 1.
- 166 -
In present case the r a m and cylinder were designed for
load of 150 tonnes with an oil p re s su re of about 25,000 psi acting on
4" diameter r a m . The diametra l clearance between the r a m and can-
nis ter was controlled to 0.2 mm.
The par t s of the hydraulic jack were fabricated out of
EN-24 alloy steel . The par t s were machined to close to lerances ,and
accuracies of dimensions were maintained to 0.01 mm.
The mater ia l in annealed condition was rough turned
providing sufficient allowance for grinding after heat t rea tment . The
par ts were hardened and tempered to a hardness of RC50. Rough
and finish grinding were car r ied out on lathe with tool-post g r inders .
Final lapping was carr ied out on lathe with alumina power of 0.5
micron size with special lint free cloth and distilled water to obtain
surface finish of 0.5 microns .
Quality control and inspection wing of Reactor Research
Centre inspected the par t s to verify dimensional conformity of the
finished p a r t s . Replicas of all sealing surfaces taken with technovit
powder were measured on Taly-surf and the surface finish was
found to be around 0.45 micro (R. M. S. value).
- 167 -
12. METALLURGY
12.1 Stress Rupture Unit for Biaxial Test ing of Clad Tubes (Baldev Ra j , C.K. Iyer , P.Kalyanasundaram,D.K.Bhat ta~ charya and P . Rodriguez)
A s t r e s s rupture system for biaxial test ing of clad tubes
of F.BTR fuel pins has been designed. Two such systems are being
built . One of them, would be located in concrete cell No. 4 of Radio-
metallurgy Laboratory to tes t i rr idiated clad tubes and the second
unit would be located in Materials Development Laboratory to gene
r a t e data on unirradiated clad tubes . Each of the units has been
designed to facilitate simultaneous s t r e s s rupture test ing of five
tubes and burs t testing of one tube. The p re s su re in each tube could 2
be varied and controlled independently to a -maximum of 2000 kg /cm .
The tes t s would be carr ied out in either vacuum or in inert gas en
vironment upto a maximum tempera ture of 1000 C.
A group of two diaphragm compresso r s would be used
to compress the inert gas from a minimum of one atmosphere to 2
a maximum of 2000 kg /cm . The f irst one would be electr ical ly
operated and would compress the bottled inert gas to a maximum 2
of 250 k g / c m and the second one which would be an air operating diaphragm compressor would use the discharged gas from the
2 f i rs t and r a i s e the gas p r e s su re to a maximum, of 2000 kg /cm •
The discharge side of the second compressor would be connected
to a six-way distribution vesse l . Six independent lines would run
from this ves se l , five for s t r e s s rupture tes t s and the sixth for
burs t t e s t . In F ig . 12,, 1.1 only the layout of a single s t r e s s rup
tu re line from this distribution vesse l is shown. In each line the
distribution vesse l is connected to a p re s su re vessel through a
cut-out valve. The p r e s s u r e vesse l acts as a storage tank for
keeping the p re s su re constant in the tes t specimens throughout
the experiment. The p r e s su re vesse l would be connected to the
DIAPHRAGM COMPRESSOR
05 00
FIG.12-t.-1- STRESS RUPTURE UNIT FOR LMFBR CLAD TUBES .
- 169 -
specimen with high pressure tubing through a solenoid valve, a
p ressure t ransducer , a control gauge,and a threeway valve. All the
five s t r e s s rupture specimens would be heated in the same furnace
having a uniform temperature zone 'of 15 0 mm. Two LVDT's for
each specimen mounted on a stand would measure the diametral
distension of each clad tube at various axial positions during the
experiment.
Burst testing of clad tubes would be carr ied out indepen
dent of s t r e s s rupture studies. In this shor t - t e rm test , the specimen
would be pressur i sed continuously by the group of diaphragm compre
s so r s . The specimen would be housed in a separate furnace and the
data of t ime and pressure required to cause clad breach would be
determined. Total circumferential deformation of the clad at failure
would be measured accurately inside the hot cell.
12.2. Pilot Plant for Inert Gas Purification (P. Kalyanasundaram and • Baldev Raj)
Argon or nitrogen atmosphere with controlled impurit ies
would be necessary in the cells of Radiometallurgy Laboratory where
non-oxide fuel elements would be examined after i rradiat ion as part
of future advanced fuel development programme. A closed circuit
inert gas purification plant would be used to r e s t r i c t the impurit ies
such as oxygen and moisture which would increase in amount in the
inert gas through the leaks in the sea l s , and during various t ransfer
operations of mater ia ls from and to air atmospheres outside the cells .
Before the purification plant is finalised in design and details, a pilot
plant has been deemed necessary to gain experience on purification
and operational problems. The design of the pilot plant has been
completed and fabrication is in p rogress . The layout of the plant
is shown in F ig . 1 2 . 2 . 1 .
MOISTURE
02 INERT GAS
LU
4 111
2
L 13 MM OM
rfch-B 8
0
12
11
FIG.12.2.1. SCHEMATIC DIAGRAM
2 7
MM OM | U U
8
10
Vf-1
1 VACUUM PUMP
2 RECIRCULATION TANK 0-25 M3 .
3 DIAPHRAGM COMPRESSOR
U STORAGE TANK
5 PRESSURE GAUGE
6 PRESSURE REGULATOR
7 FLOW METER
8 MOISTURE AND OXYGEN SENSOR
9 HYDROGEN MIXING
W PALLADIUM CATALYST BED
11 OXIDISED COPPER WIRE
12 MOLECULAR SIEVE TYPE 5A
13 SAMPLE GAS TAKEN .-FOR HYDROGEN ANALYSIS
\L MANOMETER
o
OF PILOT PLANT FOR A r / N 2 PURIFICATION
- 171 -
Controlled quantities of oxygen and moisture would be
mixed with argon or nitrogen in the recirculat ion tank (2). The con
tents of impurities would be measured before and after their removal
from the inert gas by means of moisture and oxygen monitors . (8).
The moisture moni tors would read dew points from as low as -80 C
(0.5 ppm moisture) to -20 C (1000 ppm mois ture) , with an accuracy
of + 1 ppm or + 3 C whichever is g rea te r . The oxygen monitors
would have two full ranges . They are (i) 1 to 150 ppm, and (ii) 100
to 15,000 ppm, the accuracy being +2% of the full range . A dia
phragm compressor (3) would generate a p r e s su re of 6 ba r s which
would be suitably regulated for inert gas circulation through the entire
circui t . The moisture from the inert gas would be removed by pas s
ing the gas over a molecular sieve bed (12) of type 5A. To remove
oxygen, it will be first converted to moisture by its react ion with hy
drogen in presence of a palladium bed (10). The moisture thus generated
would be removed by molecular sieve bed (12). The excess hydrogen
from the conversion reaction would be removed by passing the gas over
heated oxidised copper wire (11). A sample of the gas would be taken
out to determine the amount of the t race hydrgen (13). The purified
inert gas would go to the recirculat ion tank (2) for further circulation.
Other methods of oxygen removal from inert gas would also be t r ied .
Follwoing studies a r e planned to be carr ied out with
the pilot plant:
(i) Equilibrium moisture loading as a function of dew
point at a given tempera ture of the s ieve. This
character is t ic is important because the dew point
of the purified argon or nitrogen depends on the
moisture content by which the sieve can be loaded
corresponding to the maximum tolerable moisture
content in the purified inert gas , one can design
the molecular sieve properly.
- 172 -
(ii) Influence of tempera ture on the equilibrium moisture
loading.
(iii) Comparative proper t ies of the indigenous and imported
molecular s ieves .
(iv) Design of suitable palladium bed and study of the opera
tional charac ter is t ics of the bed.
(v) Design of hydrogen admission and excess hydrogen
removal sys tems .
(vi) Operational problems with respect to bearing motors
and electr ical contacts in dry inert a tmosphere,
12.3 Lead Cell Facil i ty for Radiometallurgy Laboratory (K.V. Kasiviswanathan, Ba ldevRaj , D.K. Bhattaeharya and P.V„ Kumar)
A lead cell facility has been planned to c a r r y out those
metallurgical operations and examinations which require flexibility and
c loser approach between the operator and the job. The facility com
pr i ses of five lead cel ls which will handle alpha-beta-gamma radioactive
samples . Essentially the cells would be made of stainless steel boxes
surrounding which lead bricks would be piled. The boxes would act as
alpha containers and lead alloy (Pb -6% Sb) br icks of 0. 250m thickness 3
would provide shielding to the extent of 10 cur ies of 1 MeV gamma r a y s .
Dry shielding glass windows with glass panels fitted with the boxes have
been chosen to provide viewing inside the boxes. Articulated minimani-
pulators with shielding blocks in through tubes would be provided. Steel
roofs of 0. 3m thick and lead blocks in the through tubes of articulated
minimanipulators would ensure permiss ible dose level (£ 0.25 : mR/hr )
inside the air handling unit room and the office a r ea s on the first floor.
Dose levels in the operating area of lead cel ls would also be kept < 0 . 25
m R / h r . The schematic layout of ]ead cells is given in P ig . 1 2 . 3 . 1 .
Table 12 .3 .1 gives the operations planned in each cell .
o o CO
o m
3
CELL 7
£ II
v V V A V V v V V v V v . A A - V .
o ID CM
* -
o o -J (D
o o 00
T f — ^
• f 6000
2000
III
mm A
*'.C"<X>." ' - - z \ /
X
1
CM
o o
- ^
o o in
o
1300
o in CM CM
o o in CM
^ ^
Isolation area
rz N
h m
y^^y^vffX, V POSITION OF MANIPULATOR
t 1200^^ (7250
250-^ ^-150 250.
-+4^ 1200 -*v
o m CM
3
o i n CM
LT i
X
i - ^
2800 +
CO
FIG. 12.3.1. LEAD. CELL LAYOUT OF RML
- 174 -
TABLE 12 .3 .1
Lead Cell I Transfer of specimens to shielded microprobe
Lead Cell II Specimen preparat ion for election microscopy
Lead Cell III Thermogravimetr ic studies on fuel
Lead Cell IV Metallographic studies with Leitz MM5 RT
metallograph
Lead Cell V Instrumented impact testing
Pneumatic t ransfer l ines would be installed to t ransfer
(1) specimens from concrete ce l lNo 0 7 to lead cell IV, (ii) impact tes t
specimens from concrete cell 7 to lead cell V. Intercel l t ransfer sys
tems have been planned between cells I and II, and between cel ls II and
lit, and between III and IV. Sealed external t ransfer systems with proper
shielding (La-Calhene type) would be provided to t ransfer active waste
(solid and liquid)from the containment boxes.
Frogman entry facility to lead cells I and II has been
provided through the lower isolation area <of concrete cells,, Individual
man entry por ts have been provided for cells III, IV and V.
A i r conditioning and ventilation system of lead cel ls
has been suitably coupled with that for the concrete cellso Separate
supply and exhaust blowers (100% stand by) have been provided for
these ce l l s . During the design stage, due care has been taken so that
changeover from air environment to inert-gas environment in the cel ls
would be easy.
- 175 -
12.4 Leak Test Apparatus for Irradiated Fuel Fins (C.K. Iyer and Baldev Raj)
An apparatus, to facilitate through a sensitive method,
the location of leaks in irradiated fuel pins, so that detailed micro-
structural examination can be carried out at the failure* positions, -•9
has been designed. The aim is to get a sensitivity of 10 std 3
cm / sec. SFR leak detection method has been chosen in preference
to helium leak detection method to avoid stray signals from other
failed fuel pins in the testing cell , (Helium is used as a filling gas
in the fuel pins during fabrication.) Radiation Technology and
Industrial Application Section of Isotope Group, Bhabha Atomic Research
Centre would supply SFR leak detector and probe required for the
apparatus. We have designed a p ressure chamber which would be
used for filling 90:10 mixture, of SF„ and nitrogen at p ressure upto 2 6
120 kg/cm . The pressurised gas mixture would go into the fuel
pin through cracks if any. The fuel pins, after sufficient t ime in
the pressur is ing medium, would be taken out and flushed with ni t ro
gen. Probing with SF„ detector would be then carried out to find
the location of the failure and to assess the leak ra t e . Electron
absorption property of SFR gas is used by the detector for detec
tion and quantitative estimation of the leak. Figure 12.4. 1 gives
the assembled view of the pressure chamber. P re s su re chamber
(1) about 1.2 met re long, r e s t s on a base plate (2) and holds the
fuel pin. An adaptor (3) holds the pressure chamber and also the
fuel pin (4). The pin being long ( ^ 500-1000mm) is guided by
two holders inside the pressure chamber. One side of p ressu re
chamber is permanently closed whereas at the other end, a gas-
keted swivel bracket is used to close the* pressure chamber
during pressur isat ion. Insertion and re t r ieval of the fuel pin is
done through the gasketed end by means of a specially shaped tong.
The fuel pin is drawn out on'the two guides (5), and is probed
for leak detection after flushing with nitrogen.
1000
vmrwmimM.u'ux.'JiJ- - 4 —
-=^v? T
T 1500
-a
o o • *
'
I r»=-Fi
' I : 11 I I
—
4-_-' : —
— 1 I
1. PRESS
2 . BASE
3 . ADAPT
UF
PL
OF
RE CHAME
ATE
\.—*
H I i
J. 1
5 .
_U r r r r :
j
1
FUEL PIN
TWO GUIDES
'FIG.12.4.1. LEAK TEST APPARATUS ( LTS )
- 177 -
12.5 Proof Testing of End Plug Weldments of FBTR Clad Tubes (C.K. Iyer, Baldev Raj and D . K . Bhattacharya)
To assure sufficient mechanical strength of the end
plug weld of FBTR fuel pins fabricated by the qualified welding
method adopted at Radiometallurgy section, Bhabha Atomic Research
Centre , a set up has been fabricated and commissioned. The
principle lies in internally pressur is ing the end plug weld specimen
by argon or helium gas at 500-800 C and in the pressure range , 2
14-20 MN/m for an appropriately specified length of t ime. In
c a s e , the weldment does not fail within this t ime the weldment
and the welding procedure are considered to be sound. The pressure
and the temperature can be controlled accurately in each experiment.
The layout of the setup is shown in Fig. 1 2 . 5 . 1 . The
high p ressure is obtained by introducing argon or helium gas in the
line from the gas cylinder A and equalising the p res su re in the line
with that inside the gas cylinder. This method pressur isat ion has
been adopted since no diaphragm gas compressors a re available
with us presently. The safety aspects in this case have been con
sidered and proper care taken thereto.
The specimen B is kept at the central uniform tem
pera ture zone of a three zone furnace with air atmosphere. When
the argon gas p ressu re is equalised between the specimen and the
argon gas cylinder, a hand operated two way valve C cuts off the
line from the argon cylinder. The furnace is then switched on.
The p ressu re (indicated by p ressure gauge D) and temperature
(indicated by thermocouple) a re noted at regular intervals.
Two specimens have so far been tested. Metallogra-
phic investigations to find out the nature of failure a r e in p rogress .
The resu l t s of these investigations will enable us to suggest improve
ments needed if any in the welding procedure.
A = ARGON GAS CYLINDER
B = SPECIMEN -
C - TWO WAY VALVE
D = PRESSURE GAUGE
I § s
REDUCER
I =•=
FURNACE —
COOLING COIL
-QUICK COUPLING
t
c»
FIG.12.5.1 END PLUG WELD STRENGTH TEST
- 179 -
12. 6 Clad Tubes with Experimental Specimens (S. L.Mannan, Baldev Raj , D.K. Bhattacharya, S.K.Ray and C.K.Iyer)
The design of an experimental pin has been undertaken.
The pin which is the same as FBTR clad tube, would contain experi
mental specimens within it.
Fig, 12. 6. 1 shows the experimental pin with the
various specimen c lus ters and other pa r t s . The following list gives
the types of specimens and other -parts which would be introduced
into the pin:
(i) Tension specimens (A); Dimensions 50 x 30 x 0.37 mm
(gauge dimension: 25 mm).
(ii) Specimen for t ransmiss ion electron microscopy (B).
Dimensions 20 x 30 x 0.37 mm
(iii) All weldment specimens (C); Dimensions 3 mm dia x
4 mm. height.
(iv) Flux and temperature monitors (D)
Each individual type of specimens would be held to
gether in the form of c lus ters by means of appropriate holders . The
c lus ters would be stacked one above the other with spacers in between
them. The spring at the top would keep the c lus ters firm in position
during t rans i t ' and handling. The spacers would facilitate t ransverse
cutting of the pin during post : irradiation examination without damaging
the specimen c lus te r s . Specimens for (i) s t r e s s rupture studies (ii)i '
r ing tensile t e s t s and (iii) Na-corrosion studies would be obtained from
the clad tube itself.
5-1 O.D.
@ TENSILE SPECIMENS CLUSTER
(D ELECTRON MICROSCOPIC SPECIMENS CLUSTER
©.WELDMENT SPECIMENS CLUSTER
© TEMP./ FLUX MONITORS t
SPACERS
FIG. 12.6.1. CLAD TUBE WITH" EXPERIMENTAL SPECIMENS ( C.T.E.S )
- 181 -
The feasibility of fabrication of the tiny specimens
and other parts which would go inside the pin is being studied. The
objective is to incorporate one or more such experimental pins
containing specimens from actual mater ia ls used in FBTR as well as
from candidate mater ia ls for future r eac to r s , in the first core itself.
12.7 Computer Based Gamma Scanner for FBTR Fins (Baldev Raj , P . Rodriguez, M.G. Fhadnis*, B .N.Karkera* , Venugopal*, D. Brahmachari* and C.K. Pithama*)
The work on this project has continued in the year
mainly with respect to the commissioning of a TDC-312 computer ,
coupling ADC interfaces with this computer and obtaining sample
spectra from radio-isotopes using the already commissioned system
and Nal(Tl) detector. Detailed design of bench and collimator a s
semblies have also been completed and drawings are being prepared.
A low activity pin having fission products of our interest in desired
ra t ios is being fabricated by Isotope Division, Bhabha Atomic Research
Centre and this pin would be used for prel iminary cal ibrat ions.
F igure 12 .7 .1 gives the details of the pin.
It has been decided to incorporate mag tape system
in order to .enhance the versal i ty for acquiring more reference spectra
from irradiated fuel pins. Feasibility study is being made to a s s e s s
the possibility of using the TDC-312 computer with mag tape system
for quantitative metallography and energy dispersive x - ray analysis .
REFERENCE
1. Computer-based Gamma Scanner for FBTR P ins , Activity
Report 1975, RRC-19, (1977) p . 144.
* Reactor Control Division, Bhabha Atomic Research Centre.
5-1 O.D.
K ^ S K \ \ \ V t t S N ^ S ^ ^ 531-5
^ PACKING POWDER
n RADIOACTIVE ISOTOPES+U0Z
03 CO
FIG. 12-7.-1 LOW ACTIVITY CAPSULE FOR CALIBRATION OF COMPUTER
BASED GAMMA SCANNING SETUP.
- 183 -
12. 8 Puncture Chamber for Fiss ion Gas Extraction f rom Irradiated Fuel Pins (P.Kalyanasundaram and Baldev Raj)
As part of the design and fabrication work for the set
up for fission gas extraction and analysis from irradiated fuel pins
a fuel pin puncture chamber has been designed and is being fabricated
F i ss ion gases from the fuel pins would be extracted after puncturing
the pins at their plenum a reas with meahcnical dr i l ls enclosed within -6
the puncture chamber evacuated to 10 to r r (Fig. 12. 8.1). The dr i l l
would be driven axially by a rotating driving->-rod. Since the accuracy
of measurement of fission gas quantity depends on minimum dead volume
and minimum outgassing ra t e of the puncture chamber, their designed — fi
values have been kept at the minimum possible i. e. 85 CC and 2 x 1 0
to r r~ l i t r e s /min . respectively, Teflon 'O' r ings have been chosen to be o
used as high as 200 C.
REFERENCE
1. K . V . Kasiviswanathan, P . Kalyanasundaram and Baldev Raj ,
Design of Fiss ion Gas Collection and Measuring Setup,
Activity Report 1975, RRC-19 (1977), p . 146.
12.9 X-Radiography of Irradiated Fuel Elements (C.K. Iyer , D.K. Bhattacharya and Baldev Raj)
As part of the overall nondestructive test facilities to
be available in RML, an X-radiographic setup has been planned.
This would be used as a complementary technique to that of neutron
radiography. Whereas neutron radiography gives, in general ,
images with better resolution and contrast for the fissile par t of
the fuel pins* x-radiography gives bet ter resolution and contrast
for the non-fissile par t s of the pin (plenum a rea , spring e t c . ) .
1. PUNCTURING UNIT
2. CAP
3. FUEL PIN
4'.- FUEL PIN HOLDER
5. TOOL DRIVING ROD
6. COVER
7. TOOL HOLDER
8. TOOL.
FIG .1 2 .8 .1 . FUEL PIN PUNCTURING CHAMBER
- 185 -
The X-radiography setup would be housed in the con
cre te cell No. 5 of RML and in the room below it. The fuel pin
would be t ransfer red from cell 5 to the room below where a 420 KV
X-ray source would be installed. The imaging of the pin would be
car r ied out on the bas i s of a "s t r ip" technique in which the X - r a y s ,
attenuated by the moving fuel pin would fall on the film (moving
at the same speed as the fuel pin) in the corm of successive " s t r i p s " .
The conceived layout is shown in F ig . 1 2 . 9 . 1 . The
fabrication of the different components necessary for the setup would
s tar t shortly. The principle of operation would be as follows. The
casset te A holding the fuel pin would be moved vertically from, cell
5 down into the room below by means of a chain dr ive . There would
be two sprockets for the dr ive . One would be -positioned in cell 5
and the other inside the tube B which would form an "extension" of
the cell 5 and would provide alpha containment. The fuel pin c a s
sette A would be fixed to the chain and would move with the l inks.
To reduce the fogging of the film by the gamma r ays from the fuel
e lements , lead brick shielding wells C, would be provided. Also,
the film would be so chosen that it would have relatively more sen
sitivity for X- rays than for jT-rays.
The fuel pin casset te A. and the film casset te D would
be: moved synchronously by means of the motor E provided with limit
switches. The " s t r ip" images would be formed by the X- r ays pa s s
ing through the cut out F on the lead brick shield. The film cas
sette side of the shielding would have a door 'G' which would enable
the loading and unloading of the X- ray film.
It has been estimated that the geometric unsharpness
would be < 0 . 1 mm.
- 186 -
FIG.:12;i9.r. POST IRRADIATION X-RADIOGRAPHY OF . F BTR FUEL ELEMENTS :; •
- 187 -
12.10 Neutron Radiographyr NDTT for Radioactive Objects (Baldev Raj , C.K. Iyer , P . Kalyanasundaram, C. S. Passupathy"1' Y .D. Dande* P . Rodriguez and G. Venkataraman**)
Neutron Radiography has emerged in recent yea r s as an
important non-destructive testing technique for post- i r radiat ion examina
tion of highly radioactive objects. It has been proposed to install in
RML a swimming pool type reac tor of 30kW thermal power in the base
ment of concrete cell No. 3 and use one of the two collimated outputs
from this reac tor for neutron radiography of radioactive objects such
as conventional wire wrapped subassembly, grid type subassembly, fuel
pins and control r o d s , The other collimator would be used for inactive
objects. The conical coll imators would have a length of 1800 mm and 2 2
a variable aperature (1 cm to 25 cm ) at the core end. Thermal and epithermal flux levels at the object end would be of the order
6 7 - 2
of 10 - 10 n / cm / s e c . Indirect neutron radiography technique
with dysprosium/indium foil and di rect radiography with lithium bora te -
coated cellulose ni trate films will be tr ied for fuel pins and control
rods . However in view of the hexagonal nature of subassembly, it
has been planned to adopt only lithium borate coated cellulose ni trate
film to neutron-radiograph them.
This note gives the details of r ig being planned for
the iiieutron radiography of active objects. Fig . - 12 .10.1 depicts
the driving arrangement and F ig . 12.10.2 shows the casset te a r range
ment.
* Neutron Physics Section, Bhabha Atomic Research Centre
## Materials Science Laboratory, Reactor Research Centre
188
DRUM-
iffo. 0 JL
—ggj
3 C
-PULLEY
-WIRE ROPE
) F>1
MOVING }— CAGE
-u-v-FIG.12-104 NEUTRON RADIOGRAPHY RIG.
(DRiVE MECHANISM)
ir
- 189 -
The object along with indexed cadmium sheet would be
held on a moving cage about 1.75 m long. The moving cage would
have guides to match the ones on the outer containment. The outer
containment would act as an integral leak tight system connected to
the floor of hot cell No. 3 and would have less thickness at the posi
tions where the neutron beam enters and leaves. A stepper motor
would be used for driving/lifting the cage with the object. The
choice of the stepper motor has been based on the objective that
encoding of the position of the object would be accurate thereby facili
tating planning of overlapping exposures. Two limit switches would
be provided to ensure safety when the cage reaches its l imi ts . Resolu
tion expected for encoding the position of object is 25«-m.
Figure 12.10.2 shows schematically the casset te feed
ing arrangement. Seven casset tes with t ransfer foils would be held
in a chain riding over two sprockets , one on either end of the con
tainment tfcbe. One of the sprockets would be driven by a shaft which
would get its motion from the main shaft running perpendicular to it.
A cam would be fixed on the main shaft,. The t ravel of casset te and
the top end of cam would be fixed in such a way that when the casset te
is in front of the collimator opening, the cam from its top end would
push a piston which would bring the casset te near the containment tube
and hence enabling to obtain better resolution in radiographs. As the
object t ravels further down, another casset te would be .positioned for
next radiograph. This sequence of operations has been planned so as
to avoid minimum operator entry in reactor and neutron radiography
r o o m s Rotation of the stepper motor would be encoded. When the
cage comes to desired position of interest for exposure, the motor
would be stopped. Meanwhile the casset te would come in position
and would be pushed by piston. This would be followed by the opera
tion of opening of the beam shutter automatically. "After the desired
t ime of exposure a the beam shutter would be closed. All the above
said sequence of operations is proposed to be done with various
- 190 -
CASSETE
CAM-
SPROCKET CHAIN
SHIELDING
GUIDES
3=e-
r MOVING CAGE
OUTER CONTAINMENT BOX
FIG. 12.10.2, NEUTRON RADIOGRAPHY RIG ( N.R.R)
- 191 -
time delay circui ts . The operations would be remotised and controls
would be located in operating area in front of cell No. 3. Boral plates
would be suitably positioned to prevent scattered neutrons from affecting
the transfer foils.
12.11 Metallographic Examination of Austenitic Stainless Steel Weldments (S. Venkadesan and V.S . Raghunathan)
Metallographic examination of stainless steel welds essentially
involves the characterisation of ferr i te in the weld with respect to its
morphology, content and composition . The detectio of microcracks (2,3)
and non-metallic inclusion are other aspects of interest ' . Fe r r i t e
in the weld is usually a metastable phase and its composition is not
homogeneous. Besides, it is nori-unifbrmiy distributed in the weld in (4)
the form of fine particles having • preferred orientation
The present study is intended to obtain information on the
extent of inhomogeneity of composition and distribution of the ferr i te
in welds. Besides, the effect of further thermal treatment to the
welds on composition and structure is being studied. Optical micro
scopy and electron microprobe analyses a r e the techniques used in
the investigations.
Type 316 stainless steel sheets , 3 mm thick, were used as
base metal for the welds. TIG and MMA. processes of welding were
employed. Welds were made by single pass welding as per geometry
shown in Fig. 12 .11 .1 . The chemistry of the weld deposit was varied
using different electrodes as given in Table 1 2 . 1 , 1 .
- 192 -
5
V l A2 A3 HHS
" Nj
2 «* •»
/
A7' A
f
3-2
5
i
1
LONGITUDINAL SECTION AA
REGION
FERRITE %
RANGE OF FERRITE
A1 A2 A3 V ' A5 7 10 7 10 7
3-11 5-15 2-12 5-15 2-11
CROSS SECTION BB
REGION
FERRITE %
RANGE OF FERRITE
B, B2 B3
10 8 9
4-13 5-12 4-15
FIG.12.11.1. THE WELD GEOMETRY AND AMOUNT OF FERRITE IN THE LONGITUDINAL-
. AND CROSS - SECTIONS
- 193 -
TABLE 1^.11.1
Composition of the Weld Pad
Process Variable
Elec t rode/Fi l le r Wire
C - 0.029
Mn - 1.8
P-0 .035 Max.
S-0.012 Max.
Si-0.70
Cr -17 .0
Mo-2.25
Ni- 11.90
Tungsten Inert Gas TIG
Manual Metal Arc (MMA)
308 Fi l le r
(Mc Kay Ltd. - UK)
316 F i l l e r
(A-121, Advani Oerlikon)
304/308 Fi l ler (A-120. Advani Oerlikon)
E 308L - 15
(Oerlikon-Basic Coated)
E 308L - 16 (Oerliikon. Rutile coated)
The ferr i te contents were evaluated using metallogra-
phic method. Both the c ross sections and the longitudinal sections
were examined. To refer to a specific instance, where welding
procedures used was TIG, with 316 filler w i r e s , the variation of
ferr i te content in the c ross section and longitudinal sections is
shown in F ig . 1 2 . 1 1 . 1 . The morphology of ferr i te in the untreated
welds were predominantly dendritic as seen in the photomicrograph in
F ig . 12.11.2(a). The variation of the ferr i te content in different
regions can be attributed to the different cooling ra tes obtained
during solidification of the weld pool.
In general , the chemistry of the weld and heat t reat
ment affect; the average ferr i te content. Heat t rea tments were
-194-
_3M_
ffflpztt 2(u*ijv
7^
v 'S- J
«. * ' \ »»\ >>.-"i'v *i
30;U
Fig .12 .11 .2 . Photomicrograph ahouring the morphology of f a r r i t e . (a) in as u/elded condition (b) af ter heat treatment at 11 CIO °C for 24 hrs.
- 195 -
given to samples cut from the weld pad in the range 900-1100 C
for varying lengths of t ime . In general , there is a reduction in
ferr i te content as well as a spherol disation of fer r i te . This is
shown in photomicrograph hx Fig. 12 .11 . 2(b) (sample same as that
shown in F ig . 12.11.2(a) but t reated at 1000°C for 24h).
Compositions of fe r r i t e , austenite and base metal
were determined using an electron microprobe analyser . The
concentration of Cr , F e , Ni and Mo in ferr i te were not uniform
throughout the c ross section of weld examined. The spread of
concentrations a re shown as his tograms in F ig .12 .11 .3 and 12.11 .4 .
Heat t reatment of welds at elevated tempera tures
resu l t s in spheroid isation as weli as a reduction in ferr i te content.
This is to be expected as the metastable ferr i te would dissolve
during heat t reatment result ing in a stable austenite phase of uni
form composition. However, the microprobe resu l t s obtained by
us indicated that this was not so. It can be seen from the isto-
grams shown in Fig. 12.11.3 and 12.11.4 that for the heat t reated
samples there is a noticeable increase in chromium content of
fer r i te . Such a situation may be detr imental for elevated
tempera ture application ( ^ 7 0 0 C ) because of the fact that
the ferr i te r icher in chromium may act as nucleating s i tes for
the formation of sigma phase thereby accelerating its formation
and growth. If some amount. of cold work is given to the piece
pr ior to its high temperature application susceptibility to sigma
formation will increase further.
REFERENCES
1. W.T . Delong, Welding Journal _53, 273-S (1974).
2. C D . Lundin, W.T . Delong and D . F . Spond, Welding Journal
5 4 , 241-S (1975).
- 196 -
(a)
(b)
2 4
MOLYBDENUM
FIG..12.11. 3 HISTOGRAM SHOWING FREQUENCY vs
CONCENTRATION Fe,Mo IN THE WELD
(a). BEFORE HEAT TREATMENT
(b) AFTER HEAT TREATMENT AT 1100 °C, 5 HRS
- 197 -
CHROMIUM
FIG.12.1U HISTOGRAM SHOWING FREQUENCY vs CONCENTRATION OF Cr,Ni IN THE WELD (a). BEFORE HEAT TREATMENT (b) AFTER HEAT TREATMENT AT 1100°C.
5 HRS . '
- 198 -
3. F . C . Hull, Welding Journal J52, 193-S (1973).
4. F . Wallner, F . M . Oberhauser and R. Schimbock, Prakt ische
Metallographie JJ2, 407 (1975).
12.12. Creep and Tensile P roper t i e s of Type 316 SS Cladding Tubes for FBTR (M.D. Mathew, K.G. Samuel, S .L. Mannan and P . Rodriguez)
Creep and high tempera ture tensile t es t s on clad tubes
for FBTR procured from three different sources have been undertaken
to provide data to Fas t Reactor Group for the design of the core and
also to generate base line data to find out the effect of i rradiat ion
on mechanical proper t ies of clad tubes. Results of tensile t e s t s at
600,650 and 700 C, on tubes from supplier 1 (see Table 12.12.2
for details like chemical composition, condition e tc . ) a re shown inTable
12.12.1
TABLE 12. 12.1
Test Tempera tu re °C
600
650
700
Tensile Tes t
Oi.2% Y.S .
MN/m
253.9 246.2
259.8
255.9 284.4
Results on
UTS
MN/m 2
598.8 599.7
523.5
414.2 421.9
Clad Tubes
Uniform elongation
%
30.9 31.8
25.3
13.8 18.1
Total elongation
%
30.9 31.8
25.5
24.3 27.6
- 199 -
TABLE 12.12.2
Chemical Composition and Finished Condition of Clad Tubes
Chemical Analysis Supplier 1 Supplier 2
wt %
C
C r
Ni
M o l
Mn
Si
P
S
0.063
17.28
13.53
2.28
1.60
0.51
0.005
0.004
0.050
16.70
13.15
2.08
1.57
0.48
0.012
0.005
Final 13.3 - 13.7% solution condition cAd worked annealed
Size 5.10 + 0.013 mm.OD 5.10 + 0. 03 mm.OD
X 0. 37 + 0. 013 mm. 0,37 + 0.02 mm. wall thickness wall thickness
Ductility, par t icular ly the uniform elongation falls with
t empera tu re . Serrated flow behaviour was observed at t empera tures
of 600 and 650 C while at 700 C serra t ions were absent. Fur ther
t es t s at other tempera tures and on clad tubes from other sources
a r e in p rog re s s .
Results of creep tes t s at 700 C on tubes from supplier
2 (See Table 12.12.2 for details) a r e shown in Fig 1 2 . 1 2 . 1 . Minimum
creep r a t e s have been evaluated from nominal s t rain ve r sus t ime
plots and Fig . 12. 12.2 shows the plot of log minimum creep ra te
ve r sus log s t r e s s . The creep law at 700 C for these tubes as"
- 200 -
, — — . —. —: .. ~v. , -. , , .• ; ' r •'
o -
r £ i -6 -o I tu -12 -Q. E
pu>i -18 -
• -2A -
-30 -
- 3 6 ' .
' • ' • • ' ^ ^ ^ • • • • ' • • '
*j2r®
- • • • • • ^ s ^ ' • - " . ' ' . . • . . . . " ' • _ •
\ s ^ •"'''''
> ' ^ " ^ ^ ' • ' : I
• •• ' : 1 • ' 1 " 1 1 1
10 • 20 30 40 : 50
. ' " :'•'. . Injff" ( MN/m2fJ ' '.., . ' •
• FIG. 12.12.2.In MINIMUM CREEP. RATE VERSUS. In STRESS. PLOT ; .
/ ;' ;.•"' ..AT 700*C FOR CLAD TUBES FROM SUPPLIER-2..
• 0 ' w "
..0^6 -
, b-ifl -
E- '
•E'. •'• . E
z '.0-32 •
u.
in ;;'0;.24-
'••'•\, ! ; 6'16;
.:'. 0-08'
• ; ' 1 ' ' • ' • . . • ; . . ' ' • ' . ' • ' ; . . . . • ' • ' . ' • ' . • • ' ' .
' • ' '..'
- ,;. , 1. U3 M N / m 2 ' . • 7 ' . ' ¥*> :'••'.'>•;•;.: ' : • ' • ' .
. 2. 116 M N / m 2 / . ' ' • • • / ' ! : • :•'•.'
1 3. 98 MN/m2 J / ' ; , . '
J (,. 78 MN/m2 / • / '
- . ' , ' • ' / 5. 59 MN/m2 / / ' • ' ' , .
/ • TEMPERATURE 700 C • / . / '
. " ' ' • " • / , • ' ' ' ' , ' . ' ' - . ' ^ s ^ •^^^"^ "•'"• •''•'''
/ ' . ' • ^ ^ ^ ~ ~ • • i - " • ' * : • . • • • • • : • . ' ' . ' " • • " ' .
/ ' ' • • ^ ^ ^ ' — * • , • ' - • - - * - 5 . ' • • ' : . • • • • •'
V .300 ' . 600 900 '1200 .*T500 .:•;•'. '.;-; •
" ' . ' -'.':' / ' : , ' ' ..:. '. ' ..:•;•-. ; ; ' . ' • ' '' TIME ( HRS ) ' ••'• ' . ' ' ' \.'".;:'::".'-;- .'' ••'
':.;;:FIG:12..12.1, STRAIN VERSUS TIME PLOTS. AT 70D°CAT VARIOUS STRESS
":.: ,, J ;.:;;• ''-;-r'-';.;• LEVELS FOR CLAD TUBES FROM.:J5UPPLIER-2-V j . - > U v-.'
- 201 -
determined from Fig. 12.12.2 is
/^ 1 on -lr>~16 _ , 6 . 2 8 Q = 1 . 2 9 x 10 ff^
min
12. 13 Effect of Cold Working on Mechanical Proper t ies of Virgo 1458 (Type Algl 316 SS) (G. Bandopadhyay, S. L. Mannan and P . Rodriguez)
The study of the effect of cold working on tens i l e ,
impact, hardness and creep proper t ies of Virgo 14 SB base mate r ia l
has been undertaken. These investigations include the effect of cold
work on various mechanical proper t ies of welded jo in ts , and also
the study of possible detrimental effect of cold work on the sens i
tization in the heat affected zone (HAZ) in welded s t ruc tu res . The
main objective of this p rogramme is to determine the amount of
cold work that can be allowed in fabricated components of FBTR
without resor t ing to heat t rea tment .
Pla tes of 20 mm thickness were given var ious degrees
of cold work from 5 to 15% (as measured by reduction in thick
ness) by rol l ing. Hardness measurements were taken on these
cold worked plates and the variat ion of hardness in VPN (50 kg
load) as a function of cold work is shown in Fig . 1 2 . 1 3 . 1 . This
variat ion of hardness can be used to ascer ta in the degree of cold
work in actual components. Fig. 12.13.2 shows the variat ion
of room tempera tu re Charpy (Cv) impact values with the degree
of cold work. Impact energy decreases with cold working more
repidly at low degree of cold work than at high degree of cold work.
The sca t te r observed in impact values could a r i s e from nonhomo-
geneous cold working. The effect of -.cold work on t ens i l e , c reep
and corros ion proper t ies is under investigation. Welding of the
cold worked plates has been completed to study the influence of cold
work on sensit ization in HAZ.
. " . - - ' V ' . ' . " ' _ '"-*•' '. " ' ; . : . - ' . " ,Vv." ; - . 0 >•-.-'•'.-ir-"; . - . ~'.'r- ':.'-•, •• '• "• " - '
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: ' ' • ' ' ' • • • " ' ' . ' . ; - • ' •
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' .* ; UJ ' , - . ' " . • . — i * - •
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£'• 200 .:. Z .
• ^ • •.' 1 — •
o •
V t • . - 2 - -•
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100
• " " ; ; ' . • ; ; . : •. ." '" ~':~ V " : " ' ' , , i - ' ; : •.-'.-.-' [ - . ^ ' J . ; '•. '•>'< ' : ' iy . . - " ; " ' ' . v'-; :" - . '
•-; '• .•" .'.'• ' •;• .-.' •'•'-'V,.'/;•.:'•.".':'- }• '••-"'' '.i . .'
' • • ' " ' • " • ' * - • • • - : . . . ' . . ' • ' '• ' •
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\ -• • \ - : ~ '-':-•'' ' • ' :
• " - . . * \ . . . - - . - ' ' ' ; " - - ; - ' • . • • ; . - ^ , . - . j - ' . • * ' \ \ ' ' ,"• ' ' ' ^,
- . - ' - .•' \ N . ^ V ' ' ',
^^. -o '• X . -r
• . . . . ^ * L • ' ' - - ' . ' • ^*^^_ '
•'-'"' ^ E ^ « ^ w
- ' • • ' : • ' ' • • ' " ' . • • ; : ' " : ^
' . " - . . • » " • .
• i " • "• - - " i • . " - - ' i •
• •-:. •• ;•. 0 .- ' .5 ••".10". . ; •'; .15
'\.-.,''• ' • * . . • . ; . '' % ' COLD WORK '-'.. '" : ' : "
FrG;l2,U.2.VAr^IAtlON OF IMPACT ENERGY (Cv) ••'*•''. 4 '• -•
.WITH C6LD WORK FOR VIRGO 14SB S5
_
- •••. . . v - ' : " . " .
". •*: ' • . . . ' " . ' ' - • . . ' •
-',.'.
260
z 240 Q .
> ~
0 1 CD LU z •-Q '
< 220 I
200
ifln 0 .
FIG..12.13.1.
• - - ^ •
' ' • ' ' ' : ' "
/ o
0 /
y ' ~ ''
/ "' '
^ r
• B
/ O . -
/ ! * * f
rr^ . ; :; . .;•:
r • " i '. • ' • ' • . - - . . ' •5 . ' 10 . ,15. :
.' % COLD WORK . ' • . ';•', "•'
VARIATION OF HARDNESS WITH;.
COLD WORK FOR VIRGO USB SS
(S3 O to
rig.12.14.4. Microstructure near the fracture end of creep tested samples of 316L S.S. (100X)
Fig.12.14.2. Microstructure of 316L S.S. after 4 hours at 1100*C. Grain size 140tt77U (100X)
Fig.12.14.5. Microstructure at shoulder region of creep tested samples of 316L S.S. (100X)
- 2 04 -
12.14 Effect of Grain Size on Creep-rupture Proper t i es of AISI 316L SS (S. L. Mannan, K.G. Samuel and P . Rodriguez)
The effects of grain size on the high tempera ture mechanical
proper t ies of austenitic s tainless s teels have not been investigated in
detail . Limited data on the c reep r a t e s of an austenitic s tainless s teel
indicate a c r i t ica l grain size at which steady state creep ra te is mi
nimum . Rupture life has been reported to decrease with increase in
grain size , but by analogy with c reep r a t e , a maximum in rupture
life with grain size is to be expected. In fact, since the majority of
the investigations on the effect of grain size on creep behaviour of
mater ia l s have included only a narrow range of grain size usually lying
on either side of the cr i t ica l grain s i ze , the resu l t s and conclusions
have been contradictory. The present studies have been initiated
with the intention to employ a wide range of grain s i ze s . Methods
of producing different grain s izes form part of the study.
Solution annealed type 316L stainless s tee l , having a grain
s ize of 23 jbm was the s tar t ing mate r i a l . Larger grain sizes have
been obtained by further annealing at higher t empera tu res for varying
lengths of t imes (90 juris , at 1200°C for 20 minutes; 100 fOro a t
1150°C for 1 hour, 1 2 5 ^ * ^ , at 1150°C for 2.5 hour s , 140 tCrl\ ,
at 1100 C for 4 hours and 185 j^n\, at 1200°C for 3 hours) . F o r
producing smal ler grain s i z e s , recrys ta l l iza t ion after cold working
has been t r i ed . One interesting metallographic observation during
the grain growth kinetics studies is that the extent of annealing twins
in 316L SS decrea-.-~ j with grain coarsening (Figs . 12 .14,1 and
12 .14 .2) . The behaviour is s imi lar to that reported in copper in
which annihilation of annealing twins occurs during further grain
growth
The resu l t s of s t r e s s rupture t e s t s on 23 LCrt grain size
J I L_J • i i i i i : i i i i i i i i : i L_ . 1 0 . 100 . . . . . . ; • 1000
. . . t R RUPTURE. LIFE, HOURS. . v .
FIG, .'12.Y4.-3... STRESS RUPTURE.PLOT FOR TYPE 316LSS (GRAIN SIZE 23jum)
J
- 206 -
at t empera tu res 650 and 700 C a r e shown in Fig . 1 2 . 1 4 . 3 . Linear
i so therms a r e obtained in the plots of log (T vs log t^ (rupture
life). Typical r esu l t s of metallographic studies on the tested sam
ples a r e shown in Fig . 12.14.4 and 12 .14 .5 . Fig , 12.14.4 which
is from the gauge region near the f rac tu re , shows t^at the fracture
is intergranular and that the annealing twins have disappeared.
Fig, 12. 14, 5 is from the shoulder region of the tested sample and
offers a better comparison with the micros t ruc ture in the pretes ted
condition (Fig, 12.14.1) as the grains a re s t i l l equiaxed. With the
pads provided in the shoulder region, the s t r e s s the re was only 2 2
33r,7mm compared to the s t r e s s of 147.9 N /mm in the gauge
section. It is interest ing to note that the annealing twins have been
eliminated h e r e a l so , thus indicating that plastic deformation may
not be a prerequis i te for the elimination of twins at these t empera
t u r e s . However, as indicated ea r l i e r , the shoulder region was 2
under a s t r e s s of 33 N / m m (within the elast ic limit) and we a r e
carry ing out further studies to find out whether the twins a re
annihilated at the t empera tu res of tes t with no s t r e s s at a l l . More
c reep tes ts and grain growth studies a r e also in p r o g r e s s .
REFERENCES
1. F . Garofalo, W. F . Domis and F . Von Gemmingen, T r a n s . Met.
Soc. AIME, J230, 1460 (1964).
2. V .V. P . l iutumbarao, S. Lele and P . Rama Rao, T r a n s . IIM,
21_, 1 (1974).
3. G. Gindraux and W. F o r m , J . Inst . Metals , 101, 85 (1973).
- 207 -
12.15 High Tempera ture Tensile Behaviour of Vir^ ) 14 SB (Type AISI 316 SS) (K.G. Samuel, S .L. Mannan and P . Rodriguez)
Tensile t e s t s have been car r ied out on three heats of Virgo
14 SB (Type AISI 316 SS) s tainless s tee l , a mater ia l used in the fa
brication of various FBTR components. Test ing t empera tu res ranged
from 30 to 750 C. These studies were aimed at providing data to
Fas t Reactor Group of RRC obtaining base- l ine data for future studies
on the effects of irradiation and sodium environment on the tensi le
proper t ies and understanding deformation and work-hardening me
chanisms in the mater ia l .
Typical r esu l t s of the variat ion of yield s t r e s s (YS)
ultimate tensi le strength (UTS), uniform elongation, and total elonga
tion with temperature for one heat of Virgo 14 SB a re shown in
F ig . 1 2 . 1 5 . 1 . Both YS and UTS show a general decrease with t em
pera ture but a plateau is observed in the tempera ture range of
350-550°C for YS and a sma l l peak around 450°C in UTS. Both
uniform and total elongation show a decrease with tempera ture with
a smal l minima around 250 C beyond which the curve r i s e s and
falls again. Uniform elongation continuously dec reases at higher
t empe ra tu r e s , but the total elongation exhibits a plateau above 650 C.
Serrated yielding has been observed in the tempera ture range of
550»650 C. Work hardening charac te r i s t ics have been analysed at (1) (2)
var ious t empera tu res employing Hollomon , Ludwik and modi-(3)
fied Swift equations. Analyses based on all the th ree equations
reveal two stages of work hardening at lower t empera tu res and
single stage hardening at 700 and 750 C. Transmiss ion electron
microscopic studies of the substructure a r e in p rogress to under
stand the flow behaviour.
-"208 -
>
^ 40 o
20
c*» E £
CD z Ui
&200 o _ J
>-
100
O TOTAL ELONGATION
© UNIFORM ELONGATION
600-
100 200 600 300 400 500
TEMPERATUREfC
FIG.i2.15.l.STRENGTH AND DUCTILITY VARIATION FOR : VIRGO USB (TYPE 316SS) WITH TEMPERATURE.
700
- 209 -
REFERENCES
1. J . H . Hollomon, Trans* AIME, JLj^, 268 (1945).
2„ P . Ludwik3 Elemeute der Teehnologischem Mechanik, (Julius
Springer, Ber l in , 1969), p . 32.
3„ H.W. Swift, J. Mech, Phys , Solids,, 1, 1 (1952).
12= 16 Relative Effectiveness of Creep Rupture P a r a m e t e r s for AISI 316 SS (Go Bandropadhyay3 So L. Mannan and P . Rodriguez)
Various t ime- tempera ture pa rame te r s have been proposed
for the interpolation and extrapolation of creep rupture data. The
aim of the present work is to evaluate the re la t ive effectiveness of
commonly employed pa ramete r s like Larson-Mil ler , Orr -Sherby-(2) (3)
Dorn and Manson-Haferd p a r a m e t e r s . The effectiveness of the pa ramet r i c approaches has been determined in t e r m s of the accuracy achieved in extrapolation of sho r t - t e rm data to predict long- te rm
(4 5) behaviour. Published s t r e s s rupture data * of AISI 316 SS was
used for this analysis . As graphical evaluation of pa ramet r i c con
stants involved in various pa rame te r s has been shown to be l ess
accurate and also subject to individual judgement, numerical m e
thods have been adopted in this study. The following two methods
have been employed.
i) Manson and Mendelson's Least Squares Optimisation A ( 6 )
Procedure ii) Manson's Optimisation Procedure using Orthogonal
Polynomials
The data used in the analysis a r e : t empera ture range
- 210
T A B L E 1 2 . 1 6 . 1 .
SI. No .
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
1 1 .
12.
13.
14.
15.
16.
17.
18.
19.
20.
2 1 .
M i n i m u m \
Ref. • a .
AAA
AAB
AAC
AAD
AAE
A A F
A A L
M M
AAN
AaA
A a B
ADA
ADB
ADC
ADD
A D E
ADE
Standard
NRD Stee l K (27BKK)
NRD S tee l -C(23BCK)
G R D - S t e e l K(27BKK)
G R D - S t e e l C (238BCK)
R e f e r e n c e (4) R e f e r e n c e (5)
D e v i a t i o n s B a s e d on the
Method (i)
L a r s o n -M i l l e r
m i n .
0 . 073791
0 .13493
0 .12070
.10569
0 .10260
0 .11595
0 .075463
0 .11002
0 .10577
0 .096917
0 .046127
0 .067489
0 .065514
0 .084192
0 .069978
0 .14580
0 .11237
0 .30733
0 . 8 3 6 4 1
0 .50462
0 .47823
for S e r i a l N o s . 1 for S e r i a l N o s . 18
O r r - S h e r b y - D o r n
m i n .
0 .058466
0 .065515
0 .10135
0 .071504
0 .080706
0 .091442
0 .052705
0 .086455
0 .079029
0 .077427
0 .042480
0 .049360
0 .046217
0 .066593
0 .053 840
0 .126380
0 .11116
0 .37389
0 .84187
0 .51552
0 .45608
t o 17 to 2 1 .
Two Methods
Method
L a r s o n -M i l l e r
m i n .
0 .0647
0 .0969
0 .1230
0 .0985
0 .1140
0 .1220
0 .0806
0 .1170
0 .1100
0 .1010
0 .0500
0 .0714
0 .0681
0 .0904
0 .0752
0 .1480
0 . 0 8 2 1
0 .1960
0 .7660
0 .4960
(ii)
M a n s o n -Hafe rd
m i n .
0 .0526
0 .0670
0 .0607
0 .0678
0 .0402
0 .0402
0 .0540
0 .0528
0 .0691
0 .0354
0 .0552
0 .0427
0 .0437
0 .0399
0 .0424
0 .0868
0 . 0 3 1 1
0 .1640
0 .3480
0 .3550
- 211 -
2 of 750-1250 K, s t r e s s range of 20-550 N / m m and rupture l ives of
0 .1-80,000 h. The correlat ion of experimental data and the ext ra-
polative ability of the pa ramet r i c approaches has been deterr.vmed
using Manson and Mendelson's Leas t Squares Approach for Larson-
Miller and Manson-Haferd p a r a m e t e r s . It has been found from the
l a t t e r that the Manson-Haferd pa ramete r cor re la tes the experimental
data bet ter than the Larson-Mil le r pa r ame te r . The minimum stan-(5)
dard deviations calculated for different se t s of data based on m e thods (i) and (ii) a r e shown in Table 1 2 . 1 6 . 1 .
In order to determine the relat ive effectiveness of the
p a r a m e t e r s , Manson's optimisation method employing orthogonal
polynomials is being used for Dorn pa ramete r as "well.
A recent ly proposed graphical optimisation procedure (7)
(GOP) i s a l so being attempted to determine the re la t ive effectiveness of var ious pa ramet r i c approaches. Extrapolation of s e condary c reep r a t e data will also be car r ied out. In addition to the data on AISI 316 SS, the data on other nuclear grade ma te r i a l s will also be evaluated.
REFERENCES
1. F . R . Larson and J. Mil ler , T r a n s . ASME, _74, 765 (1952).
2. R. L. O r r , O.D. Sherby and J . E . D.orn, T r a n s , ASME, _46, 113
(1954).
3 . S. S. Manson and A . M . Haferd, NASA-TN-2890, March, 1953.
4 . NRIM Creep Data Sheets: No. 6, 1972; No. 14, 1974; No. 15 , 1974.
5. A. Mendelson, E. Rober t s , J r . and S.S . Manson, NASA TN-D-
2975 (1965).
6. S.S. Manson and A. Mendelson, NASA Memo-3-10-59E (1959).
7. D.A. Woodford, Mat. Sci. and E n g . , 15, 169 (1974).
- 212 -
12.17 Stress Relaxation in Super Pure Aluminium (S.K. Ray and P. Rodriguez)
Super pure aluminium (better than 99.99%) specimens were
deformed in tension to various levels of plastic strain and then
allowed to undergo stress-relaxation for periods of upto 1000 seconds
Experiments were conducted at three temperaturesj RT, 91 and 171 C
The load-time data were analyzed using a spline function. Plots of
log plastic strain rate vs s tress indicated that the activation area
remains either constant or decreases with decreasing s t ress . In
view of this , it is postulated that a recovery process is operative
down to the lowest test temperature. Preliminary calculations in
dicate that a diffusion controlled "static" recovery mechanism cannot
explain the observed phenomenon. A new model which assumes
cross-slip as the dynamic recovery mechanism is being developed.
12. 18 Influence of Preheat Temperature on .'Stellite Deposits (M.D. Mathew, S.K. Gupta* and S.L. Mannan)
The influence of preheat temperature on Stellite deposits
on types 304 and 316 SS has been studied. The stellite grade 6
bare rod was used and oxyacetylene welding process was employed
to prepare the overlays. The metallurgical evaluation of various
deposits included optical-metallographic investigations, microhard-
ness measurements and electron microprobe studies on the stellite
deposits, the interface between stellite and base, and the base ma
terial.
The deposit on AISI 316 SS prepared by employing a pre
heat temperature of 150 C followed by still air cooling revealed
some undesirable features like microcracks and porosity in the
stellite (Fig. 12,18.1 - Fig. 12.18.4). Chemical analysis of the
* Construction Group, Fast Breeder Test Reactor
-213-
Fig.12.18.1. Hicrostructurs of Stel-lite showing porosities. Preheat at 150oC.(20Xj
Fig.12.18.2. Microstructura of Stel-lite/base metal interface. Preheat at 150°C.(100X)
Fig,12.18.3. Microstructure or Stel-lite/baae metal interface showing microcrack in stellite. Preheat *t 150°C{100X) •
Fig.12.8.4. Microstructura of Stel-lite/base metal junction showing microcrack at interface. Preheat at 150°C<100X)
-214-
flg.12.18.5. Mlcrostructure of stallite without porosities. Preheat at 900"C 100X
fig.12.18.6. nicrostructure of stelllte/base matal interface. No defect. Preheat M 900»C. 100X
----- \f if*:-:
Fig.12.18.7, Microstructure of b88e metal. No defect. Preheat at 900BC 100X
• Co 9 Cr X W
100 U
o o
2 60 < or
en UJ
FIG. 12:18.:8. DISTRIBUTION OF
ACROSS SAMPLE
X' >Fe;'•• <: =c;:s •;.;.}'. :•.,• ;...' £->,:© Ni':>:Y-;-N^:^--;-: ;;•:.:•;•-:;;•";.-;,:•'• . " v . - •-. . . . •?;:.'" VHN^:v.;rV.':-'A..Vv :'M^ X. ';•.'•-"
JU4 b o ^
^^,,0---<i>^^Q^x©^«0«_^-«-0--O _
800 S
' . 2
600 S UJ 2 O <r
400 J
UJ
200 y >
r
250 ' 300 350 400 450 . ( MICRONS )
ELEMENTS AND MICRO HARDNESS
AT: 900°C;. PRE HEAT - • • ' • - / • • . . ' . ' " " ' •
1
to
!
- 216 -
deposit indicated that the re has been carbon pickup during deposition
due to the carbur is ing flame used.
A higher preheat tempera ture and slow cooling was con
sidered necessa ry for avoidance of microcracking. Another s tel l t te
deposit was prepared on AISI 304 SS employing a pre-heat tempera
ture of 900 C, followed by air cooling to about 450 C and then fur
nace cooling to room tempera tu re . The optical metallographic exa
mination of the stel l i te showed the absence of c racks or porosity
(Pig. 12 .18 .5 - Fig . 12.18. 7). Microprpbe analysis was car r ied out
to study the distribution of various elements in the stell i te and
ac ross the interface into the base. The resu l t s a r e shown in Fig.
12 .18 .8 , in which charac ter i s t ic x - r ay intensities from different
elements versus distance along the microprobe t r a v e r s e for var ious
elements a re shown. Microhardness measurements have been taken
along the microprobe t r a v e r s e and the resu l t s a r e shown in the
same figure. It can be seen that a correla t ion exists between the
microhardness and the cobalt content of the deposit .
12.19. Studies on Sensitization of 316 SS (R.K. Dayal, S. Venkadesan and J. B . Gnanamoorthy)
The extent of sensitization on VIRGO 14 SB (316 SS) is
being investigated with a view to develop Time-Tempera ture -Sen-
sitization (TTS) diagram and to determine optimum dimensional s ta
bilization t reatment for FBTR grid plate. The extent of sensi t iza
tion is evaluated by determining the susceptibility to intergranular
cor ros ion as per ASTM standard A262 pract ice A and ASTM stan
dard A.393. This consists o f a screening tes t by electrolytic etching
and corrosion tes t in a boiling (10% CuS04 + 10% H SO ) solution
for 72 hours . In the present studies the specimens from the a s -
received VIRGO 14 SB plates were heat - t rea ted at various tempera tures
217
O NO'ATTACK BY Cu SO/,/ H2 SO^ TEST
9 LIGHT ATTACK BY do
• SEVERE ATTACK BY do
<§> NO ATTACK BY Cu/Cu SO^ / H2 SO^ TEST
@ LIGHT ATTACK BY do
© SEVERE ATTACK BY do
'. ; 1000
• 950
900
L 850
800 \ ° z 750C
£ 700
< 650 cc •• • LLl
2 600
*" .550
.500'
, .450
: 400 • . •'* • ' • • .• o
, „ • , • ' ' . . .
- 0 O O
- ° o © o ©. o o o o
® &/*& ® ^^^^s^o o o
) o © *© • • • • * ^ ^
© ® \ \ ® ® ° o o ^ N ©
, O w ^ ^ ^ ^ « o • • • '•
o o ® ©*•>..
- ' • • • • . '
1 t - 1 ' 1
•1 • 1-0- •• 10 . .100 ' 1000
' ' TIME IN HOURS *~ .
..FIG..12.19.1.TIME TEMPERATURE CORROSION . DIAGRAM .•' \:S^i; '•;••' FOR VIRGO USB STAINLESS STEEL
- 218 -
ranging from 500 C to 950°C in steps of 50°C and for various lengths of
t ime ranging from a few minutes to 1000 hours . The heat- t reated speci
mens were tested for intergranular corros ion according to the above
s tandards . F r o m the data obtained a TTS diagram has been plotted and
is shown in F ig . 12 .19 .1 (dark line).
Since ASTM standard A 393 has been withdrawn, the t e s t s
were repeated (for the border line data in F ig . 12.19.1) according
to ASTM standard A.262 pract ice A and pract ice E. This standard
is s imi lar to the ea r l i e r mentioned standard except that the speci
men is embedded in copper chips and exposed to a s imi la r solution
for 24 hours . Use of copper in contact with the specimen makes the
test much more severe due to the galvanic cell action. The TTS
curve has been slightly modified by obtaining data from the above
tes ts and is also plotted in F ig . 12 .19 .1 (dotted line). F r o m this
curve it can be seen that use of Cu chips has resulted in slight
shift of the curve towards the left. To complete the full loop, t e s t s
for longer durations (greater than 1000 hours) a r e in p rog re s s .
12.20 Investigations on a Failed I-Beam (R.K. Dayal, J. B. Gnanamoorthy and P . Rodriguez)
The work on the investigation of the catastrophically
failed I -Beam reported ear l ie r was continued. A few more in
vestigations were car r ied out and the resu l t s obtained a r e summa
r i sed below :-;
(1) Chemical Analysis :
Chemical analysis of the steel in the flange a rea has also
shown a high carbon content (0.5%) but lower than that in the.- web
a rea (0. 62%). The chemical analysis at core and edge a reas of the
web have shown segregation of C, S and P elements into the core region.
- 219 -
The resu l t s of chemical analysis and sulphur pr ints have
indicated that the beam was rolled from r imming s tee l whereas the
IS 226 specification demands the use of killed or semikilled quality
s teel .
(2) Metallographic Examination
Besides the micros t ruc tura l examination of web c ross
section ca r r i ed out ea r l i e r , micros t ruc ture of flange c ros s section
was also studied. This has indicated a uniform micros t ruc ture
(0. 5% C) in contras t to the micros t ruc ture at web where it had shown
a high fer r i te content at the edge decreasing to a low value at the
cent re .
(3) Impact Tes t s
Charpy Impact tes ts at higher tempera ture upto 200 C were
ca r r i ed out. The re su l t s indicated that the nil ductility t ransi t ion
(NDT) tempera ture was well above the room tempera ture ( -"v/ 80 C).
<4) Tensi le Tes t s
Tensi le t e s t s on specimens taken from web and flange
a r e a s were car r ied out. The tes t r esu l t s have shown much higher
strength and lower ductility than one would expect from a ma
te r i a l with IS 226 specification. Tes t s were also car r ied out on a
good I -beam. The resu l t s a re shown in Table 1 2 . 2 0 . 1 .
220
TABLE 12 .20 .1
Results of Tensi le Tests
Sample Position
Yield Strength
2 k g / m m
26
67
42
31
30
Tensi le Strength
2
kg/mm
42 - 54
94
81
48
46
Elongation
%
23
15
19
37
34
IS 226 specification
Web (failed beam)
Flange (failed beam)
Web (good beam)
Flange (good beam)
(5) Residual s t r e s s estimation
This type of catastrophic I-beam failure has been at t r ibu-
(2)
ted to the presence of res idual s t r e s s e s by Campus . In the p r e
sent case of failure we have observed a curvature in the beam pieces
after f rac ture . One piece (3400 m m long) had a deflection of 22 m m
at the cen t re . Tensi le t e s t s have also shown difference in proper t ies
of web and flange. This difference may be due to a possibility that
during roll ing the web was cold worked while the flange was hot
worked. This differential working might have introduced res idual
s t r e s s e s within the beam.
The conclusions of the above investigation were that a
number of factors have operated simultaneously to cause the f rac
t u r e . They a r e as follows :
(1) The beam mate r ia l did not conform to IS 226 specification
for chemical composition and mechanical p roper t i e s .
- 221 -
2. The beam was rolled from r imming steel ingot instead
of killed or semikilled ones.
3. The carbon content of the beam was too high.
4. The N . D . T , t empera ture for the beam mater ia l was
well above the room tempera ture ,
5. Significant amount of res idual s t r e s s e s were present
within the beam. The s t r e s s e s were in an integral
equilibrium before flame cutting. After the cutting,
operation, this equilibrium was disturbed and the
res idual s t r e s s e s were rel ieved by splitting the beam
in two halves,
REFERENCES
1. R.K. Dayal, <LB. Gnanamoorthy, Activity Report 1975, RRC-19,
(1977), p . 140.
2. F . Campus, Residual S t resses in Metal and Metal Construction,
ed. W.R. Osgood, (Reinhold Publishing Corp. New York, 1954),
p p . 1 - 2 1 .
12.21 Interaction of Stainless Steel with Tel lur ium and Cesium. (A.S. Khanna and J. B . Gnanamoorthy)
To simulate the interaction of fission products with the
fuel clad tube in fast b reeder r eac to r fuel e lements , out of pile
experiments were ca r r i ed out using tubular capsules of s tainless
s teel type 304. The fission products used in the different experi
ments were as follows: (1) Te alone (2) Te + C r 2 0 (3) Te +
Csl and (4) Te +CsI + C r „ 0 , Calculated amounts of ces ium
(As Csl) and te l lur ium in the powder forms were added into these
- 222 -
capsules, and encapsulated in evacuated quartz tubes. They were then
heated at 650 C for 400 hours before the S. S. capsules were sectioned
transversely. The depth of penetration due to the interaction of the
fission products was determined by optical metallography, and the ex
tent of penetration by the individual fission product elements was
assessed by electron microprobe analyses.
From the results obtained, the following tentative conclu
sions were reached: (1) Tellurium can attack the stainless steel
even in the absence of an oxidising agent. In the presence of an oxi
dising agent, the attack is more pronounced. (2) When cesium is
present together with tellurium in a ratio 1:1, the extent of attack
is not significantly different from that due to tellurium alone. (3)
Cesium by itself causes little damage whereas it penetrates to a
considerable depth when an oxidising agent is also present.
12. 22 Development of an Electrochemical Technique for Determining Delta"Ferrite Content in Stainless Steel Weldments (T .P .S . Gill, U.K. Dayal and J. B. Gnanamoorthy)
The presence of delta-ferrite at certain optimum levels
in stainless-steel weldments renders them less susceptible to mi-
crofissuring and hot cracking » while increase in tensile strength
and resistance to s t ress corrosion cracking is observed at higher
ferrite levels
The approximate delta-ferrite content of a specimen can
be determined by magnetic, optical metallographic, x-ray diffraction, (4)
Mossbauer scattering methods and from. Schaeffler or DeLong (5) diagrams based on the chemical composition of the specimen,
whereas the absolute content can be determined by the electroche
mical technique. This technique also fulfils the long-standing need
-223-
3135/1 X320 > 9 — '
25« x400
5/* X2000 Sfl X2000
Fig.12.22.1 (a) Optical Photograph, (b), (c) and (d) SEM Photographs of S - Ferrito in Austenitic Steel Walda.
- 224 -
for calibration of other techniques and facilitates the morphological
studies of delta-ferrite.
The austenite phase in austenoferrite specimen can be
dissolved selectively in an aqueous medium containing sulphuric acid
(3.6N) and ammonium thicocyanate (0.1N) by raising the specimen k
potential close to, but lower than the Flade Potential and maintaining
it potentio-statistically constant ( — 80mV vs SCE) . Under these
conditions delta-ferrite phase remains in a passive state while only (7)
austenite phase dissolves • In our studies two specimens from
the same stainless steel weldment were dissolved for two and seven
teen hours respectively and their surfaces examined under a scann
ing electron microscope with a view to study the morphology of
delta-ferrite: The SEM photographs (Fig. 12. 22.1(b), (c), (d))
show the three dimensional network of the ferrite whereas optical
metallograph (Fig. 12.22.1(a)) indicates the discrete ferrite parti
cles. The austeno-ferrite and austenite interface is shown (Fig.
12.22.1(b)). That the delta-ferrite morphology varies from ooint .
to point even in the same weldmenj is seen from Fig. 12.22.1(c) and
Fig. 12.22.1(d).
A specimen was completely dissolved by keeping the po
tential constant potentiostatistically for 72 hours. The residue which
was magnetic in nature was separated and-weighed. The delta-
ferrite content was found to be 2.655 w/o as compared to 3.95 w/o
by optical metallography method. The compacted delta-ferrite was
anodically polarized in the sulphuric acid and ammonium thiocyanate
medium. The polarization diagrams of pure austenite and pure delta-
ferrite (Fig. 12. 22. 2) demonstrate emphatically the validity of the
electro-chemical technique.
- 225 -
.
- O - AUSTENITE
-+• 6 FERRITE
1*
;•''.'• , io"1 / io° ' " i o \ • 102
. '. CURRENT. DENSITY ( mA/cm2) .
FIG-12. 22.2. ANODIC' ..POLARIZATION DIAGRAMS OF .: :
: r v ; :':. AUSTENITE AND £ - FERRITE .SAMPLES
- 226 -
Detailed morphological s tudies , distribution of elements in
both phases with variat ion of de l ta - fer r i te content and comparison of
different techniques of de l ta - fer r i te determination a r e envisaged.
An attempt is also being made simultaneously to find out
a redox system in which the aus teno- fe r r i t e specimen will have the
open circui t potential corresponding to a potential for maximum se
lective dissolution of austenite. Effect of oxygen concentration, t em
pe ra tu re , concentration of Cu(II) and Fe(III) ions and galvanic coup
ling with copper and platinum were studied but the des i red potential
could not be achieved. However, an aqueous sys tem containing a
mixture of chloro complexes of Cu(I) and Cu(II) holds some promise
of selective dissolution of austeni te . Fur the r work on this sys tem
is in p r o g r e s s .
REFERENCES
1. F . C . Hull, Welding Jou rna l , 4_6, 399-s (1967).
2. W . T . DeLong, ibid, _53 (7), 273-s (1974).
3 . H . F . Reed and W . T . DeLong, Metal P r o g r e s s , 107(6), 73
(1973).
4. L. L. Schwartzendruber, L. H. Bennett, E . A . Schoefer,
W . T . DeLong and H. C. Campbell , Welding Journa l , 53(1),
l=s (1974).
5. A. Mudde, Phil ips Welding Repor ter , 4 , 10 (1973).
6. T .G . Gooch, J. Honeycombe and P . Walker , B r . C o r r s . J . ,
j>, 148 (1971).
7. A. Bathi ly, P h . D . T h e s i s , "Contribution a L'etude Structurale
des Ac ie r s Austeno - Fe r r i t i ques - Character isa t ion Morpho-
logique et Analytique de la Phase F e r r i t i q u e " , University of
P a r i s , F r a n c e (1974).
- 227 -
12.23 Compatibility Studies on Type 347 Stainless Steel (H.S. Khatak and J. B. Gnanamoorthy)
The thermal convection loop containing tensi le specimens
of thermomechanically t reated and annealed type 347 S.S, was operated
with liquid sodium with a hot leg t empera ture of 400 C and a cold leg
tempera ture of 300 C. After 4800 hours of exposure, a leak was
detected at a weld ;in the hottest region of the loop. The loop was
shut down and the portion of the tube containing the defective weld was
cut out and after welding a new tube, the loop operation was continued.
"Visual and metallographic examinations of the failed part
revealed the following information :
1. The c ross -p ieces used for holding the specimens had
been wrongly positioned in paral lel . (See Fig. 12. 23. 1).
2. During the welding of the c ross -p ieces to the tube, there
was insufficient weld penetration.
These two conditions had resul ted in the formation of
c revices at the junction of the weld and the c ross -p ieces . These c r e v i
ces could have entrapped a smal l amount of water, during the p re l imi
nary cleaning operations, which formed sodium hydroxide by react ing
with the sodium. The attack due to the sodium hydroxide could have
resul ted in the leak. Metallographic examination of the tube very
close to the failed part showed deep intergranular attack. Ruther et
al had observed a s imi lar type of attack while examining the cause
of a leak in the 347 S.S. bellows of a valve in EBR-II.
REFERENCE
1. W . E . Ruther, T. D. Claar and R. V. Strain, Evaluation of
Mater ia ls Compatibility in the EBR-II Reactor , Corrosion by
Liquid Metals, ed. J. E. Draley and J. R. Weeks, (Plenum
P r e s s , New York, 1970).
^ T 0/
T
ELD DEPOSIT
" 1
-Vr A
CROSS PIECES FOR HOLDING SPECIMEN
/ ^
^-i/
^m \ \
7777}
A, 2 H3AP LEFT BETWEEN CROSS PIECES & TUBES
(a)WRONG' POSITION
•WELD DEPOSIT
\
^ /
^ s s s s ^ ^ w 8 7~
'A
^
•^T
7*
21
^q—a
_/4
Szz^}
\
?//?///J9M77ZZ 7,
"t (b) CORRECT POSITION
2L
FIG. 12-23-1 CROSS PIECES USED FOR HOLDING SPECIMEN IN SODIUM LOOP.
- 229 -
13. REPROCESSING
13.1 Development of a New Biamperometric Method for Uranium Analysis (G.R. Balasubramanian, A. Palamalai and T. S. Thankachan)
For control analysis of U, Pu, Th, free acidity etc. , in
high active reprocessing s t reams, the usually followed spectrophotometric
and 0 - counting methods, require high active samples to be brought
out of lead cell or suitable chemical treatments to be performed inside
the hot cell with master slave manipulators. This would lead to higher
personnel exposure and longer time for analysis.
As part of a programme for remote adaptation of ana
lytical techniques designed to overcome the above problems a compara
tive study of different electrometric and end point detections in a well (1) established oxidimetric titration of uranium was carr ied out to select
the best method for remote analysis. Biamperometric technique is one
of the few methods which has shown acceptable precision in the compa
rative study. In this method U(VI) in strong phosphoric acid medium is
reduced to U(IV) by Fe(II). Excess Fe(II) is oxidised by HNO in the
presence of Mo(VI) catalyst . After dilution U(IV) is t i trated against
K Cr O . A small constant potential of 200 mV is applied between
the two platinum electrodes and the cell current is made to flow during
the titration.
However the biamperometric method needed further inves
tigation to optimise the conditions. For instance, in the method (3) reported by Cherry the waste volume generated in titration was
rather high (Table 13.1.1) . Amperometric technique of Venkata-(4)
subramanian , though generated an acceptable waste volume, was
- 230 -
found inconvenient for hot cell operation due to the use of rotating
platinum electrodes. In our laboratory an experiment was performed
with the reagents reduced to the levels employed by Venkatasubra-
manian, which yielded a biamperometric titration curve (Fig. 13.1.1)
with no definite end point. But the addition of vanadyl sulphate after
dilution resulted in a V-shaped titration curve (Fig. 13. 1.2) with a
sharp peak at the end-point. Also this method was found to be a s -
precise as the Cherry method. Role of vanadyl sulphate in improving
the shape of the titration curve waa also investigated and it was thus
possible to predict that in the vicinity of end-point V(IV) could oxidise
U(IV) to U(VI). After all U(IV) was oxidised, V(IV) itself was oxidised
by the dichrornate. That i s , in the titration the cell current was found
to increase after U end-point due to the reversible V(V)/V(IV) redox
couple. This theoretical explanation is supported . by independent
spectrophotometry studies also. Details of the results have been (5)
published elsewhere
REFERENCES
1. W. Davies and W.Gray, Talanta, U_, 1203 (1964).
2. A. Palamalai, T. S. Thankachan and G. R. Balasubramanian,
"Remote Adaptations of Analytical Techniques in Reprocessing
of FBR Fuels, Part I: A Comparative Study of the Various
Electrometric End Point Detections in Oxidimetric Estimations
of Uranium", RRC Report under publication.
3. J . Cherry, "A Precise Amperometric Titration for the Deter
mination of Uranium Using Fer rous Sulphate as Reductant",
P. G. Report 827(W) (1968).
4. V, Venkatasubramnian and K Perumal, Proc . of the Chemistry
Symposium, Vol. II, The Chemistry and Metallurgy Committee
of the DAE (1970) 245.
- 231 -
0.7 0 0.5 1.0 1.5
VOLUME OF TITRANT IN ml.
2.0
H
FIG! 13.1.1 BIAMPEROMETRIG TITRATION CURVE
- 2 32 -
o.i-
4 0.5 IT 7T 2V 2.5
VOLUME OF TITRANT IN ml.
3'.0 — 1 — 3.5
FIG: 13-1-2 BTAMPEROMETRIC TITRATION CURVE
(WITH ADDITION OF. VANADYL SULPHATE)
- 233 -
5. A. Palamalai , T. S. Thankachan and G. R, Balasubramanian, "An
Improved Biamperometr ic Method for Remote Analysis of Uranium".
To be communicated to the Journal Talanta.
TABLE 13 .1 .1
Comparison of Various Amperometric Methods
SI. No.
1.
2.
3.
4 .
5.
13.2
Ortho-phosphor ic acid r equ i r -
M e t h o d ed for a t i t r a -tion
Davies and Gray method 40 ml
NBL method 40 ml
Venkatasubramanian method 4 ml
Cherry method 1 0 ml
Proposed procedure 5 ml
Development of Laboratory Mixer Sett lers
Approximate waste volume generated in a t i trat ion
300 ml
2 00 ml
40 ml
100 ml
40 ml
(G. R. Balasubramanian, K. Sivasankaran and M. Venkataraman)
Low hold-up micro multistage mixer se t t le rs have the follow
ing advantages: (i) A low hold-up means low inventory of process solu
tions and new processes can be investigated economically, especially
with r a r e solutions, (ii) In nuclear chemical processes low hold-up
means less radio-activity to be handled and consequent reduction in
shielding and shielded processing volume. In view of these a four
stage miniature model was designed and operated with Uranyl Ni t ra te /
Tributyl phosphate. The stages were made of perspex, with s tainless
steel impel lers and gear drive. Hydraulic stability was achieved for
wide range of flow ra t ios . Efficiency measurements a re being made
to improve mixing by changing of the impeller geometry, Design
- 234 -
details a re as follows :
(i) Stage hold-up: 10 ml;
(ii) Maximum flow ra te that can be handled: 100 m l / h r
(mixed flow)
(iii) Dimensions of each stage
Mixer: 8 mm dia x 60 mm high
Settler: 8 x 20 x 55 mm deep
(iv) Overs-all dimension of a 16 stage bank of this design
would be 100 x 150 x 500 mm.
13.3 Putee^Column. Studies (G.R. Balasubramanian, K.V. Kasipathi Rao and S.A.K. Jeelani)
Backmixing studies in pulse column were under p rogress . A
knowledge of the degree of backmixing is useful for the economic de
sign of the pulsed perforated plate columns. Backmxing studies for
single phase flow were car r ied out in a 1 m long. 5 cm dia column
having 10 sieve plates spaced 5 cm apart . The unsteady state t r a c e r
injection technique was used. 2 ml of fluorescin solution of 1 m g / m l
concentration was injected in the up-s t ream and its down-stream con
centration was measured by an on-line fluorometer. The dispersion
coefficient was found out by matching the variance of the experimental
concentration time curve with that of the theoret ical curve. The
investigation covered wide ranges of pulse amplitude, frequency and
continuous phase velocity. The attainment of maximum dispersion
coefficient (D) with respect to the aqueous superficial velocity (u)
(Fig. 12. 3.1) suggested the possibility of the existence of a l imiting
eddy size after which the eddy size decreases with increase in mean
velocity.
The increase of pulse frequency shifts this limiting value
of eddy t o occur at high velocity. The minimum dispersion coefficient
- 235 -
10
4 8
7
v in 6
u
/ 3-
2-
t>4-
A = 5.625 cm "
SYMBOL FREQ (cycles/min) © 30 • CO X 55
A • 78
0.1 • 0.2 . 0 . 3 0.4 0.5 0.6 0.7 0.8 0.9
2^, cm /sec . •-
FIG.13. 3.1 VARIATION OF DISPERSION .. .
COEFFICIENT D WITH AQUEOUS
SUPERFICIAL VELOCITY u .
- 236 -
15
H
13
12
u - 0.863A cm./ sec.
FREQ. = 30 cycles/min.
6 . 7 8 9
A. cm — — 10 11 12 13 V, 15
FIQ: 13.3:2. VARIATION OF DISPERSION COEFFICIENT
. ;.D WITH AMPLITUDE A .
- 237 -
(Fig. 12.3.2) at an amplitude of 5 cm shows that the scale of turbulence
might reach a limiting value of the same order as the plate - to plate
spacing (5 cm) and eddies formed at one plate would be broken up by
an adjacent plate.
13.4 Development of Airlift Metering System (G.R. Balasubramanian, M.S. Illangovan and K. Sivasankaran)
Work on the airlift system was continued. The develop
ment of meter ing system is an additional feature incorporated in the
airlift system. This system is to be used for the metering of radio
active liquids. Figure 1 3 . 4 . 1 gives the schematic set-up used for
the meter ing system. Liquid level in the meter ing pot (4) is sensed
by a pneumatic t ransmi t te r (6) by purge method. The t ransmi t te r
output is fed to the pneumatic controller (7) and depending on the se t -
point, the controller output acts on the diaphragm control valve (8),
thus regulating the inflow of air-l if t required. With this se t -up by
controlling the level in the meter ing pot from zero to 30 cm (12"),
a controlled out flow of 0 to 1 1pm is obtained through 3. 2 mm
orifice. By perfectly tuning the control ler , the liquid level in the
meter ing pot is maintained wi th in+ 1% of the set value. The
metered output flow thus can be obtained within an e r r o r of 1%. A
theoret ical model is being developed to describe the behaviour of
this system.
REFERENCE
1. K. Sivasankaran and N.G. Hussain, Activity Report 1975,
RRC-19 (1977), pp. 168-169.
238 -
©
©
©
5)
••-AIR
©
VENT
®
r\
1. MAIN LIQUID STORAGE TANK.
2. DE-ENTRAINMENT-CUM VENT POT.
3. INTERMEDIATE POT.
L METERING POT WITH ORIFICE PLATE.
5. LIQUID OUTFLOW LINE.
6. TRANSMITTER PNEUMATIC.
7. CONTROLLER.
8. DIAPHRAGM CONTROL VALVE.
9. MANOMETER.
10. ROTAMETER.
11. GLOBE VALVE.
AIR
FIG, 13. 4.1 AIR-LIFT LIQUID METERING SYSTEM
- 239 -
13.5 Centrifuge Development (G.R. Balasubramanian, K. V. Kasipathi Rao and S. A. K, Jeelani)
Clarification of feed solution before solvent extraction step
is a must in reprocess ing fast r eac to r fuels. A remotely operable
centrifuge to be used for this purpose is under development. The
centrifuge using a cri t ical ly safe geometry (100 mm dia. ) was run
using a mixture of copper and manganese oxides solution (2% by
weight, simulating dissolver solutions). The solid mixture used
was passing through 250 mesh. More than 90% separation was found
to be achieved at a flow ra te of 60 l /h . The same run was repeated
using activated charcoal . The separation efficiency was more than
94% in this case . Typical filtrate samples analysed for size distribu
tion gave an average size of 9 iim. Slight decrease in separat ion
efficiency was observed when flow ra te was increased from 7. 5 l /h
to 50.4 l /h . The centrifuge is being modified for continuous solid
discharge.
13. 6 Studies on.Iron Oxide Gels . (G. R. Balasubramanian,K. Sivasankaran, R. Natarajan and R. Sivasubramanian)
Adsorption of uranium from dilute solutions by a large num-(1 2)
ber of inorganic absorbents have been established ' . Iron oxide
gels exhibit good adsorption character is t ics for uranium from dilute
solutions. Several samples of iron oxide gels have been prepared
and adsorption of uranium, from nitrate medium at var ious pH values
were measured. Adsorption of thorium under s imi la r conditions were
also measured. It was found that thorium uptake is less than uranium
for the same pH. Results of the experiments a r e shown in Fig . 13,6,1.
Based on the above r e su l t s , a mixture of thorium and uranium was
contacted with a view of achieving separation between uranium and
thorium. Pre l iminary resu l t s has shown that the single stage
240 -
.SYSTEM STUpiEfi: 20 ml. OF NITRATE SOLUTIONS OF THE CATIONS CONTACTED WITH a^O.5 gmt. OF THE g«l.
50
UJ QQ
or. o in . Q <
u. o ^n cfr E 2 O i— Q. a: o Q
40-
•>
•m
20
10
: 0 0 •, •
1
1.
d
2
^—Q^
3
o
THORIUM
URANIUM
i
5 pH OF THE SOLUTION . •••
FIG .13.6 .1 .ADSORPTION ON IRON OXIDE (GELS)
- 241 -
separation factor* var ies between 1.1 to 3. 0 for pH varying from 1.5
to 3 . Suitable eluting agents were also found out. F r o m the experi
ments it was concluded that though in this method,separation has been
achieved, it has got ser ious limitations owing to the fact that the iron
oxide gels get attacked by common acids. This study was undertaken
as a part of sol-gel studies for preparation of mic ro - spheres and iron
oxide gels prepared by this process were also studied for adsorption.
REFERENCES
1. J . A. Marinsky and Y. Marens (eds. ), Ion Exchange and Solvent
Extraction, Vol. 5, (Marcel Dekker Inc. New York 1973).
2. Min-Hai Dai and W.V. Shaw Chii, Separation Sci. J. 10 (5)
633 (1975).
ratio, .of. .concentrations... Gf uranium. . . and thorium in solution after contact
*Separation factor = rat io of concentration of uranium and thorium in solution before contact
- 242 -
14. INSTRUMENTATION
14.1 Photon Counting System (K. Sunder, N. S. MurFhy, T. V. Karhikeyan and V. Subramanian)
Photon counting is a digital technique to detect light signals
of very low levels. This method uses the digital nature of discrete
pulses obtainable from t ransducers like photo mult ipl iers or" electron
mul t ip l iers . Therefore the need for analog to digital converters is
eliminated. Also better signal to noise ratio is achieved as compared
to dc amplification with RC smoothing, modulation and lock in
techniques.
Photon counting systems a re widely used in Raman spectro
scopy, fluorometry and nuclear part icle analysis. A photon counting
sys tem essentially consists of a detector, an amplifier, a d iscr imina
tor and a counter as shown in F ig . 1 4 . 1 . 1 . The detector gives out an
e lectr ical pulse corresponding to a photon striking it. The pulse is
amplified, s tretched and fed to a discriminator which gives a standard
output pulse, if the input level is l a rger than the reference level. The
output pulses are counted by a t i m e r / s c a l e r . A r a t eme te r may also
be connected to the discr iminator to monitor the count r a t e . Provision
for print-out of the digital output or x-y record of the analog output
i s available.
The system can handle negative pulses l a rger than 1 mV and
wider than 10 ns and a repetition ra te upto 10 MHz. It was tested
with the photomultiplier RCA 6810 and is presently used with a mano-
chromator for r e s e a r c h in Raman spectroscopy.
^ ^ PMT PREAMPLIFIER
MAIN
AMPLIFIER PULSE
STRETCHER
"V" ___- r_.
DIGITAL
PRINTER
nt I T P I i T n.,, U U I I U I v>"'' •
A MA 1 ri(i n i l T D U T rt
INTERFACE
D/A CONVERTEF
«9
COUNTER
'RATEMETER
INTERFACE
I • "IT
DISCRIMINATOR
X-Y RECORDER
00
FIG. U . 1.1. BLOCK DIAGRAM OF PHOTON COUNTING SYSTEM.
- 244 -
14.2 Sca ler /Timer for Fas t Counting Applications (N.s7 Murthy)
A fast sca le r -cum-programmable t imer developed for fast
counting applications is described. The sca l e r / t imer is built in a
three width module, conforming to NIM specifications. It may be
used as a frequency counter by counting for one second.
The maximum speed of counting and the pulse pair resolu-7
tion a r e estimated to be about 5 x 10 cps and 10 ns respectively. The
s e a l e r / t i m e r can accept pulses of either polarity with pulse height in
the range of 0. 1 V to 4 V and pulse width greater than 10 ns . The
present time can be selected from 10 to 5000 seconds in 1-2-5
sequence. The block diagram of the s e a l e r / t i m e r is shown in Fig.
1 4 . 2 . 1 .
The sca le r section is made up of a dual comparator, gate,
dividers, decoder /dr ivers and an LED display. The dual comparator
eliminates the need for an external switch for selection of pulse
polarity. A switch is provided \o display the intermediate number
of counts between long counting intervals . A six digit e lectromecha-12
nical reg is te r extends the counting range to 10 counts. The gating
pulse for the scaler is generated by the t imer section comprising of
a crys ta l controlled oscillator, dividers and a programmable t imer .
Fas t IC s a re used in place of discrete components, wher
ever possible, to reduce circuit complexity. A rese t switch is pro
vided for manually reset t ing the sca ler . Start and stop 'switches
a re provided to enable or disable counting. BCD outputs are made
available for use with printer interfaces. For remote operation
of s ta r t , stop, rese t and latch inhibit control points a re brought out
I/P
CRYSTAL CLOCK
DIVIDERS PROGRAMMABLE
TIMER
CONTROL CIRCUITRY
DECADE COUNTERS
LATCHES
f
DRIVER
t t t T DECODER/ DRIVERS
• • • •
J_ E.M.REGISTER
LED DISPLAY
FIG.U.2.1 BLOCK DIAGRAM OF FAST SCALER/TIMER
- 246 -
on the front panel. The time during which the gate is open is indicated
by an LED lamp. A ca r ry pulse i s available for cascading the sca ler to
another sca ler , if necessary .
14. 3 Digital Rate meter (K. Neelakantan and V. Subramanian)
Ratemeters a re very useful in many counting applications (1-3)
where the pulse ra te is to be measured or monitored . Some
such applications are. in photon counting, x - r a y spectrometry and
nuclear spectroscopy.
A digital ra temete r has severa l advantages over its analogue
counterpart . It is more accurate, the accuracy being limited only by
the clock used and the propagation delays in the control c i rcui t ry . It
is inherently l inear, whereas the analogue instruments a re very non
linear at high count r a t e s . Also the use of digital techniques allows
for greater flexibility in design leading to features like auto-ranging
and different modes of operation and display.
The input pulses to a ra temete r in most applications a re
random and usually follow a Poisson distribution. In such a case,
the s tat is t ical e r ro r in the mean ra te is 100% where n is the number
of samples . Therefore, for a given stat ist ical accuracy, it is nece
ssa ry to sample a certain minimum number of pulses, i r respect ive
of the count r a t e .
The block diagram of the digital r a temete r is given in
Fig. 1 4 . 3 . 1 . The instrument can accept TTL pulses with countra tes 7
from 10 cps to 10 cps. It is autoranging and the pulse pair resolution is about 50 ns. It can be operated as a r a t emete r or as a t imer / s ca l e r . In the ra temete r mode'it computes with a preset
- 247
l/p COUNTERS
r1' V V~i u i o r L A I
DECADE TIMER
i i
i '
CONTROL
LOGIC
COUNTER
EXPONENT DISPLAY
i '
DECODER
FIG.U.3.1. BLOCK DIAGRAM OF DIGITAL RATEMETER
TIMING COUNTER
CLOCK (lOOKHz
JLSTART o— ,
1TS70P 3
15 j CLO Q
FLIP FLOP K CL 7476
16
14
15 14 13 12 DO D1 D2 D3 DA D5 D6 07
DATA SELECTOR Y 74151
CLEAR
A1
74121 Q MONOSHOT
5 8
DECADE TALLY B
7493
l/P
Jl O/P
+ 5 '
+ 5V
FIG. 16.3:2. SCHEMATIC DIAGRAM OF DECADE TIMER
- 248 -
accuracy of 10%, 3% or 1%. As a t imer / sca le r it gives prese t gate -4 3
t imings, ranging from 10 seconds to 10 seconds, in decade s teps .
The ra te mete r is built as per NIM specifications.The counts
are indicated on an LED display. BCD outputs are also available for
connecting to a te lepr in ter . The "overflow abort ' facility incorporated
in the module helps to reject erroneous data ar is ing from sudden
increase in ra te . The crys ta l clock used in the circuit gives an.accuracy
of 0.02%.
A novel decade t imer that is made use of in the r a t emete r
circuit uses a monoshot together with a 8 line to 1 line data selector
and a counter. The schematic diagram of the circuit is shown in
Fig. 14. 3 .2.
REFERENCES
1. R.W. Tolmie and Q. Bristow, IEEE Trans , on Nuclear Science,
NS-14, 158 (1967).
2. C.H. Vincent and J . B . Bowles, Nuclear Inst. Meth. , 2-h. 201(1963).
3. M. Werner , Nuc. Inst. Meth. , 34^ 103 (1965).
14.4 Lock-in Amplifier (S. Illango Sambasivan and V. Subramanian)
In many pract ical ' applications the e lectr ical signal of in teres t
may be buried in noise. Such obscure signals cannot be extracted or
measured by normal amplifiers and volunteers . Special ins t ruments
which can enhance the S/N ra t io may be used to recover these signals
One such instrument is the lock-in-amplifier which finds wide applica
tion in optics, ul t rasonics , solid state physics and microwave e lec t ronics .
A C CURRENT
SOURCE
EXPERIMENTAL
SET UP
AC AMPLIFIER &
FILTER
PHASE SENSITIVE DETECTOR
r
AC AMPLIFIER PHASE SHIFTING
NET WORK
LEVEL
SHIFTER METER
CO
CD
FIG. 14.4.1. BLOCK DIAGRAM OF LOCK-IN AMPLIFIER
- 250 -
A lock-in amplifier i s essentially a phase sensitive voltmeter
which can measure low level ac signals buried in noise. The block
diagram of the lock-in amplifier with a built-in current source, deve
loped for res is t iv i ty measurements at high tempera tures and high
p res su res is shown in F ig . 1 4 . 4 . 1 . The current source provides a
current up to 40 mA at 1 kHz. The nominal res i s tance of the sample
is between 0. 1 and 0. 0/Ohm. The voltage developed ac ros s the sample
is amplified and fed to the phase sensit ive detector along with the
square wave reference signal derived from the current source . The
phase sensitive detector produces a dc output that is proportional to
that par t of the input which has the same frequency and phase as the
reference.
The lock-in amplifier has a full scale sensitivity of 10 uV
and an input impedance of 100 M_n- . The signal to noise improve
ment ra t io is about 45 dB. The averaging t ime constant provided
ranges from 10 ms to 100 m s .
REFERENCES
1. T. Coor, "Signal to Noise Optimization in Precis ion Measurement
System", Princeton Applied Res . Corp. , Technical Note T-198A.
14. 5 Irradiat ion Profile Controller for Radiation Damage Experiments (R. Narayanan and V. Subramanian)
Radiation damage in mater ia ls is charac ter i sed by the
change in proper t ies - be they physical, chemical, mechanical or
e lectr ical - due to radiation exposure. Study of this phenomenon '.
helps to understand and predict the behaviour of mater ia ls in rad ia
tion environments. Usually such a study is performed in an acce le
ra ted manner in facilities like Van de Graaf generator or Variable
Energy Cyclotron (VEC).
V
CLOCK
"CURRENT INTEGRATOR
-gS»
GATED PROGRAMMABLE
COUNTER
AUTO STOP
CIRCUITRY
CONTROL
LOGIC
RESET SIGNAL
GENERATOR
GATED PULSE
GENERATOR
STEPPER MOTOR DRIVE
CIRCUITRY
to Ol
STEPPER
MOTOR
FIG.U.5.1 IRRADIATION PROFILE CONTROLLER
- 252 -
The instrumentation required for radiation damage experi
ments should be capable of rocking the sample under test to different
orientations and exposing it to different radiation doses in a p rogram
med manner . The instrumentation essentially consists of a stepper
motor and its control and drive circui t ry. The block diagram of the
sys tem is depicted in Fig. 1 4 . 5 . 1 .
The radiation dose received by the sample is indirectly
measured by a current integrator . The number of output pulses from
the integrator are counted by a programmable counter which stops
counting after a preset number of counts and gives the s t a r t signal
for the stepper motor. The number of steps to be moved is p re
selected by means of a clock and counter.
The exposure can be controlled in t e r m s of charge from
100 nano coulombs to 10 coulombs. The duration of exposure is also o
programmable from 1 second to 10 seconds. Between exposures
the sample can be rotated forward or backward in s teps , variable •'
from 1 to 10, corresponding to angles of 1.8 to 18 . An autostop
circuit incorporated in the system provides the stop signal to end
the experiment after a predetermined cycle of operations.
REFERENCE
1. J . H. Worth, "The Problem of Obtaining a Uniform "Volume Con
centration of Implantations", AERE-R-5204, (1968).
14.6 Liquid Level Monitoring System (A. K. Rawat, H. S. Nagaraja and V. Subramanian)
•A digital level measuring sys tem for remotely monitoring
levels of toxic liquids in tanks is described. The measur ing range
is up to 100 cm.
- 253 -
E fc
2
> < _ j
a. LO Q
1000
900
800
700
600
500
400
300
200
100
-
-
-
f 1
(&)r
1 1 1 1 1
($r
1 1 I 1 1 100 200 300 400 500 600 700 800 900 1000
CAPACITANCE IN pF
FIG. K 6.1.
CAPACITANCE TRANSDUCER
VOLTAGE CONVERTER
l
10Kc/s
OSCILLATOR DIVIDERS
- \< 330Kc/s
i
< '
COMPARATOR
ALARM CONTROL
LOW FREQUENCY CLOCK
i i
SWEEP GENERATOR
- ^ GATE
i '
DIGITAL DISPLAY
FIG.U.6.2. BLOCK DIAGRAM OF LIQUID LEVEL MONITOR
- 254 -
A capacitance t ransducer whose capacitance var ies l inearly
with the height of the liquid is used to sense the liquid level. This
capacitance forms a part of a diode pump circuit that gives an analog
output proportional-to the capacitance. The analog voltage is digitised
by means of an analog to digital converter and displayed as a 3 digit
number using 7 segment LEDs. The block diagram of the system is
depicted in Fig. 14. 6 . 1 .
A s ta inless s teel tank of 50 cm' height and 4 cm* inner
diameter and a stainless s teel rod of 5 mm diameter were employed
as electrodes to test the circuit . The liquid used was a dilute acid
solution. The dielectric of the capacitance t ransducer was pvc of
0. 5 mm thickness . The t ransducer showed a capacitance of approxi
mately 10 pF per cm. of liquid level. The plot of capacitance vs
level is given in Fig. 14 .6 .2 . To simulate remote measurements ,
a cable 15 m long was interposed between the t ransducer and the
circuit . The accuracy of the instrument was found to be better than
+ 3%. The stability of the display was observed to be + 2 mm, per
hour after a warm-up of about 30 minutes.
14.7 Tr ip Circuit for Superconducting Magnet Power Supply (H. S. Nagaraja)
The power supply for superconducting magnets , apart from
being highly regulated and stabilised, should meet the following r equ i r e
ments :
1. The current through the magnet coil should not r i s e abruptly.
2. The power supply should be cut off when the magnet i s not
in the superconducting state to avoid heating of the coil.
3. The energy stored in the magnet coil should be dissipated
outside the magnet when the power supply t r ips .
Vr\
REFERENCE
GENERATOR
RESET SIGNAL
: CURRENT
REGULATOR
MICRO VOLT. AMPLIFIER &
CONTROL CIRCUIT < -
MAGNET
FIG.U- ?.l BLOCK DIAGRAM OF TRIP CIRCUIT FOR SUPERCONDUCTING MAGNET POWER SUPPLY.
/
- 256 -
The block diagram of the t r ip circuit is shown iu Fig. 14.7.1.
The reference generator produces a stable reference voltaga with con
trollable slope during the initial r i s e . This reference voltage controls
the current through the magnet in conjunction with a current regulator
that can supply a maximum current of 100A. The negligibly small
voltage across the superconducting coil is monitored by a microvolt
amplifier and compared in the control circuit which r e s e t s the refe
rence. Thus the current in the magnet coil is reduced to zero when
the voltage ac ross the coil exceeds the set value. The t r ip can be
set to any value between 20 and 100 u V,
A free wheeling diode connected across the magnet coil
ensures that the inductive energy stored in the coil is dissipated in
itself when the power supply is cut off.
REFERENCE
1. H. S. Nagaraja and V. Subramanian, "100A Current Regulator",
Activity Report, RRC-19 (1975).
14. 8 Power Supplies for Ion Source (B. Krishnakumar and V. Subramanian)
The power supplies required for the ducoplasmatron ion
source which wili be used as an injector to the 2 MeV Tandem
Van-de-Graaf accelera tor being built at the Centre, a r e a s follows.
1. 2 0 kV. 2mA dc power supply for the extraction electrode.
2. 3 00V, 8A dc supplies for the anode and intermediate
electrode.
3. 2 0V, 2 0A ac power supply for the filament.
o AC MAINS
o VARIAC
-
SENSE
TRANSFORMER
s }
H.V.
TRANSFORMER
TRIP CIRCUIT
COMPARATORS
-
RECTIFIER
&
FILTER
OVER LOAD
SENSOR
RELAY
CIRCUIT
- J
FIG. U . 8 . 1 . BLOCK DIAGRAM OF EXTRACTION ELECTRODE H.V. SUPPLY
- 258 -
In all these supplies, the voltage is variable from zero to
the maximum rated value. The dc supplies use var iac control whereas
the filament supply is provided with SCR control. Protection against
voltage surges during star t ing is incoproated in all the power supplies.
The extraction electrode HV supply is provided with over-voltage pro
tection as well and the block diagram of the same is shown in Fig. 14. 8
1 4 . 8 . 1 . The input voltage to the HV t ransformer is sensed by a
t ransformer , rectified, filtered and compared with a reference in a
comparator . When the input exceeds the 'tipper' set limit, the com
parator gives a control voltage that is made use of in operating an
electr ical ly latched re lay to cut off the mains supply to the HV t r a n s
former . The supply will be res tored when the input voltage is
brought down to the ' lower' set limit which is again sensed and com
pared in a s imi lar fashion in another comparator to rese t the re lay
This principle is used with slight modification for overload protection
as well. 10% overload is, indicated by a pilot lamp. In the event of
2 0% overload, a mechanically latched re lay is operated to t r ip the
mains supply and reset t ing can be done only manually.
If a floating system of power supplies is employed for the
ion source, all the power supplies have to be isolated from ground
and the isolation may be achieved through a common isolation t r a n s
former. But this necessi ta tes control of the different power supplies
at high potential and the operation becomes difficult and cumbersome.
Hence separate isolat ion. transformers a r e used and the control is
effected from the pr imary side which is at low potential.
- 259 -
15. SAFETY RESEARCH
15.1 Solution of the ANS Benchmark Problem for Gamma Ray Transpor t (D.V. Gopinath and V. Sundararaman)
Introduction
Due to the great interest in the detailed description of
radiation fields in nuclear industry, several methods to solve the radia
tion t ransport problems have been and are being developed. These
methods differ in their basic approach as well as the computational
details. Besides there is also a large variance in the basic cross
section data and methods for processing them. Fo r evaluating
the validity and . range of application of these computational
methods and data, American Nuclear Society has constituted a bench
mark group to compile in a convenient form, a limited number of
well-defined problems. The solution of a benchmark problem for
one dimensional radiation t ransport obtained with the t ranspor t code
ASFIT developed at BARC-RRC is presented here . The
problem that has been chosen '.is the radiation charac ter is t ics at
91.44 cm (5 ft) above the air-ground interface contaminated with fin fin
Co activity. Co is assumed to have an average photon energy of 1.25 MeV and the source strength is normalised to 1
2 - 3 ^ photon per cm per sec. Air density is 1.2 9 x 10 . g / c m and
3 soil density is 2.32 g/cm .
Ear l i e r studies
This benchmark problem has been studied in detail using
Moments method by Spencer , Berger and Morr is . Moments
method is a semi-analyt ical method which is s tr ict ly applicable only
for infinite homogeneous sys tems. Though the present problem does
- 260 -
involve two different regions i. e. a i r and soil, since their absorption
and scat ter ing c ross sections a re nearly the same, the system is
considered to be homogeneous in these calculations. The other method
which has been extensively used in analysing this problem is the Monte
Carlo technique. A good collection of these resul ts is given by ( 5 ) i
Garre t . "In the Monte Carlo calculations, thd' infinite" p lane ' source
has been approximated by 23 point sources each represent ing an
annular a rea . The scat tered radiation has been calculated for 10
energy groups and 18 polar angles. In these calculations, c ross
section data used is that of Hubbell and Berger
Present calculations
The present calculations are done with the Anisotropic
Source Flux Iteration Technique (ASFIT). It is an integral equation
method using discrete ordinate representat ion in energy, space and
angle. The details of the method are given in references 7 and 8.
In the present calculations 80 energy nodal points a r e used between
1.25 MeV and 30 keV. Flux and source t e rms a re represented by
12 Legendre polynominal t e rms . Fluxes a re calculated at 16 angu
la r nodes. As in the ear l ier calculations, c ross section data of
Hubbell and Berger are' used. The quantities calculated are :
(i) angle-integrated energy distribution.
(ii) energy integrated angular distribution of number and
flux densities of scat tered radiation.
(iii) energy-angular distribution of scat tered radiation.
(iv) energy, dose and number build-up factor.
. !
« 101
g
6
4 > <u
2 • 2
. u <u w
^10° ^ 8 c «— 6 > .
m 4 c a> "D
X ' 2. 2
li_
10"1 1 V
1
—
•
• • • •
o"2
FIG.'15.1.'
Present method (ASFIT)
Monte Carlo smoothed distribution y<=5>v i function
/ ° x v \ e Monte Carlo raw data /© \ X n "
/ ^ \ • * *
i \ * \ . 3 \ \
© ' * \ if * v\
7 • • • % ' / x \ . w ^V
11 ' ^ ^ ^ I N v*"»>w» , ©^--r^,
1 0 1 9
i i
1, I©
1 f i l l 1 i 1 1 1 1 1 1 1 1 2 A 6 8 10"1 2 U 6 8 10° 2 A 6 8 101
Energy (MeV)
1. SCATTERED FLUX DENSITY ENERGY SPECTRUM.
- 262 -
c CJ
"8 1 _
a> •+->
in u QJ in •
CM E u
V .
z v ^
>> ••-'
in c O)
-a X 3
A
2
Iff1
fi
6
Monte carlo smoothed average distrrbution
Present method (ASFIT)
© Monte carlo raw -data
Ax10"2 I -10 tf- L
50 75 100
9 (degrees) 150 175
FIG; 15.1. 2. SCATTERED FLUX DENSITY ANGULAR
DISTRIBUTION .
- 263 -
Present method (AS F I T )
Moments method
© Monte carlo
-1.0 -0.8 -0.6 -0-4 -0.2 0
cose 0.2 0.4 0.6 0.8 1.0
FIG. 15.1.3 KERMA ANGULAR DISTRIBUTION
- 264 -
Results and discussion
In Pig. 15 .1 .1 is given the spectra l distribution of scat tered
radiation obtained by different methods. A major digression of the
present calculations from the ear l ier values is in the region of 2 00
keV. It is well known that at 212 keV, corresponding to the first
collision edge, the scat tered radiation has a discontinuity. The mag
nitude of the discontinuity, which can be calculated exactly, is 3.40
photons/MeV/source photon. In the ear l ie r Monte Car lo calculations,
the spec t ra l distribution in the 200 keV region is obtained by making
Use of this discontinuity and intuitively interpolating between the flux
values obtained for the groups 100 to 180 keV and 180 to 300 keV.
This gross group s t ructure would smear out any non-smooth distr ibu
tion in the spectrum. The present calculation uses a modal point
r a the r than group s t ructure in the energy domain. Modal points with
the interval of about 10 keV are used in the region of 2 00 keV. Hence
it is believed that the present calculations provide a t rue r picture
of the spect ra l distribution.
F igures 15.1.2 and 15 .1 .3 present the angular distribution
of the energy-integrated number flux and kerma values of the scat te
r ed radiation. In general , the agreement between the present calcula
tions and the ea r l i e r resu l t s is good. Crit ical comparison of these
values is not possible due to the large scat ter in the Monte Carlo r e su l t s .
One point that may be mentioned here is that since ekerma values do
not vary rapidly with energy, one would expect total kerma values will
have about the same angular distribution of energy-integrated angular
flux, which is nearly symmetr ic about u =. 0. While this s imilar i ty
between kerma and number flux is observed in the present calculation,
they differ significantly in the ear l ie r calculations. '
i
- 265 -
REFERENCES
1. Shielding Benchmark Problems, ORNL-RSIC-25 (ANS-SD-9)
(1969).
2. L. V. Spencer, Structure Shielding Against Fuel Fallout
Radiation from Nuclear Weapons, NBS Monograph 42 (1962).
3. M. J . Berger , J. App. Phys. 28 , 1502 (1957).
4. E . E . Morr i s , UILU-ENG 73 5301, University of Illinois
(1973).
60 5. C.W. Garret , Gamma-ray dose above a plane source of Co
on Air/Ground Interface. Shielding Benchmark Problem 4. 0
in Ref. 1.
6. J . H. Hubbell, Photon Cross Sections, Attenuation Coefficients
and Energy Absorption Coefficients from 10 keV to 100 GeV,
NSRDS-NBS 2 9 (1969).
7. D.V. Gopinath and K. Santhanam, Nucl. Sci. & Engg. 43,
186-196 (1971).
8. D.V. Gopinath, K. Santhanam and D. P . Burte, Nucl. Sci. &
Eng. 52 (4), 494-498 (1973).
15.2 Coagulation Studies (A. R. Sundararajan and S. D. Fulpagare)
In order to study the coagulation behaviour of sodium oxide
aerosols , a se r ies of experiments were conducted in an experimental
chamber of about 1 cubic metre in volume. Sodium aerosols were
generated by heating gram amounts of sodium in a s tainless s teel
container and sweeping air over the molten sodium. Aerosols r e l ea
sed were sampled by Andersen eight-stage impactor to obtain the
part icle size distribution. A typical plot of the part icle size distribu
tion is shown in Fig. 1 5 . 2 . 1 . Mass median diameter obtained was. •
99-99 99-9 99-5 99 98 95 90 80 70 SO SO 40 30 20 10 o 5 2 1 0 - 5
9-0 80 7-0
M
4-0
o
£ 2.0
UJ • -
s »
g 06 UJ
< 0-4
«.0-3
1 1 1 1 1 1 1 I T I 1 1 1 I I . 1 1
• y.
^r%
/ <
OS -
- J 1 t 1 - 1 1 1 1 1 1 1 1 1 1 1 t 1 I I I
0*1 0-1 0 6 1 2 5 O 20 30 40 50 60 70 80 90 95 98 99 99-5
° PERCENT LESS THAN STATED0 SIZE
FI6.15;2.1.PARTICL£ SIZE DISTRIBUTION OF SODIUM OXIDE AEROSOLS
o
HO
1 , 0° a.
3 » I -§ 60 z o u
. * • • 20
,
1 \ : . : • •
•A. >>•
. 1 1 1 1 I ! "t IS W « K -7* 90 105 " 1 2 0 ""
AEROSOL 0ELAY TIME ( Mm )
FIG.I5.7ZAEROSOL CONCENTRATION VARIATION WITH TIME
0-1 i
" 99-99
o
•
0-01
-
o"
'•
99-99
-
- 267 -
0.63 mil and geometric standard deviation was 1. 9. Variation of the
aerosol concentration with time was found by taking filter paper samples
at regular intervals of t ime. A flame photometer was used for es t i
mates of sodium in these samples . A typical plot obtained is shown in
Fig. 15 .2 .2 . Initial half-time of the mass concentration was about 15
minutes. F o r an initial mass concentration of about 150 g / l'' and for
the experimental conditions, the theoret ical est imate was about 60
minutes. Low initial half t ime has resulted from leaks in the aerosol
chamber. In the new chamber designed for studying the thermophore-
tic effects on coagulation of aerosols , leaks have been eliminated.
15.3 Light Scattering Aerosol Spectrometer (S. D." Fulpagare, K. M. Somayaji and A.R. Sundararajan)
In our studies on sodium oxide aerosols , we felt the need for
an in situ aerosol part icle counting system which will determine not
only the concentration but also the part icle size distribution of aerosols .
An aerosol spectrometer designed for this purpose is based on the
scat ter ing of light from single aerosol part icle . A schematic diagram
of the light scat ter ing aerosol spect rometer is shown in Fig. 1 5 . 3 . 1 .
Optical system of the instrument is s imilar to the design given by
Sinclair. The instrument collects light scat tered in the forward
direction (around 2 0 ) . Aerosol flow system contains a sheath a i r
collimator to provide good resolution. Light scat tered by each particle
passing through the sensing volume is seen by the photomultiplier
which provides a voltage pulse whose amplitude is a function of the
part icle s ize . Par t ic le size distribution is obtained using a pulse
height analyser comprising of 2 0 channels.
An important feature of the unit is the pulse converter
which provides the interphase between the detector and the mult i
channel analyser (MCA). Pulse width of the photomultiplier output
LIGHT SOURCE
CHANNEL NO. DISPLAY
AEROSOL INLET
^-SHEATH AIR
P.M.
.LIGHT TRAP
AEROSOL OUTLET
DISPLAY "«5J-
AUTOMATIC CHANNEL SCANNER
-s* PRE-AMP
E.H.T.
DECODER ^8~
SCANNING RATE
—^0 LINEAR AMP
PULSE SHAPER
I CHANNEL
SELECTOR
COUNTER
—T~ TIMER
FIG.15.3.1.AEROSOL LIGHT SCATTERING SPECTROMETER
- 269 -
i s controlled by particle velocity and is in the order of 1000 sec with a
slow r i s e time while the MCA accept pulses with a r i se time of not more
than 8 sec . Pulse converter consists of a circuit that converts the
amplifier pulses into sharp pulses with pulse heights equal to the peak
of the signal. The peak of the input signal is stored in a low leakage
capacitor and when the peak is reached, the voltage held is sampled
for 50 sec and t ransfer red to the 20 channel analyser . After, this t ime
interval , the reset t ing of the capacitor is initiated and the system is
ready for the next pulse. Pre l iminary tes ts with DOP aerosols of 0.8
urn size gave a mean pulse height of 1 volt. Calibration of the unit
for par t ic les of bigger sizes will be car r ied out by aerosols produced
from a spinning disc aerosol generator.
15.4 Ultrasonic Level Indicator (T.S. Neelakantan and K. M. Somayaji)
The instrument detects liquid levels continuously by ul t ra
sonic remote sensing and is part icularly useful.in those applications
where it is desirable that no external element be inser ted into the
liquid column or the container. The ultrasonic probe used is a PZT
crys ta l of 1 MHz frequency, mounted at the bottom of the vesse l .
A block diagram of the instrument is presented in Fig. 1 5 . 4 . 1 .
An ul t rasonic pulse is t ransmit ted through the medium and is received
after reflection from the free surface of the liquid. The same probe
is used both as t ransmi t te r and receiver . This excitation is repeated
at a pre-determined r a t e . The time interval between the t ransmit ted
and received pulse is a function of the liquid level and the velocity of
the ul trasonic wave in the medium. If the la t ter is assumed constant,
then the t ime interval can be calibrated directly in t e r m s of the liquid
level.
' " ' . • • ' • - " • - • ' " • • ' .
OSCILLATOR TRIGGER CIRCUIT
ii
" ' '
PROBE
,
.
AMPLIFIER
DELAY
CLOCK
MONOSTABLE
GATE
FLIP FLOP
FLIP FLOP
GATE
PULSE SHAPER
'
ANALOG OUTPUT
C O U N T E R
'' ' D 1
•' ' S P L A Y
FIG.15.4.1. ULTRASONIC LEVEL DETECTOR
- 271 -
The weak reflected signal received by the probe is amplified
by means of a high frequency amplifier and gated through an analog
gate so that only the first reflected pulse passes through the gate. The
transmit ted pulse and the first reflected] pulse after wave shaping,
respectively set and rese t a flipflop thus generating a pulse width. A
standard clock is gated for this period and counted by a four digit
counter and displayed. This clock is of variable frequency, thus enabl
ing the system to be calibrated for any liquid at a par t icular tempera
ture .
Both analog and digital readouts can be incorporated in the
above instrument. The' instrument has been tested in a s ta inless
steel container. The instrument, as designed now, has a range of
upto 2 mete r s with a resolution of 1 mm and does not have tempera ture
compensation. The range can be further improved by improving upon
the amplifier gain and increasing the t ransmit ted power. Temperature
compensation can be incorporated by continuously monitoring the rat io
of the above said pulse width with another standard pulse width derived
from the sys tem and calibrating this ra t io in t e rms of the level. This
standard pulse width can be obtained by monitoring the diameter of
the vesse l .
- 2 72 -
16. ENGINEERING SERVICES
16.1 Central Workshop
During the year -machining and fabrication of components
required for FBTR and various other units of RRC were carr ied out.
Some of the major components fabricated and machined at Central
Workshop were :
(1) Fabricat ion of s teel vessel for FBTR-,
(2) Fabricat ion of plug and sleeve for dismantling cell
for FBTR,
(3) Fabricat ion of base plate for active building ra i l for
FBTR.
(4) Fabricat ion of dismantling cell penetration for vacuum
pump and cable for FBTR.
(5) Dismantling cell embedded sleeve for Master Sleeve
Manipulator for FBTR.
(6) Fabricat ion of pit for storage of empty pots for FBTR.
(7) Dismantling cell embedded sleeve for Per iscope for
FBTR.
(8) Fabricat ion of top shield sub assembly outer body
(control post) for FBTR.
(9) Dismantling cell toboggan for FBTR.
(10) Development of deep hold boring process for core
cover plate and drive mechanism.
- 273 -
(11) Fabricat ion of camera t r ack , machining of par t s for
autoclave and ion source , fabrication of table and
compensating arrangement for angular correlat ion
machine, liquid nitrogen t r a p , revolving chalk board,
microfilm r e a d e r , m i r r o r mount, sample chamber
for Laser Raman Sr<3ctror;;.3tor, high p r e s su re optical
> cell for Materials Science Laboratory , RRC.
(12) Stainless s teel chamber for electr ic discharge study,
fabrication of stainless steel, feed vesse l for Safety
Research Laboratory.
(13) Fabricat ion of serv ice s leeve , service plug and blank
plug for hot cel l , shielding block for exhaust ducts ,
exhaust duct and door l iner for hot cell for Radio
Chemistry Laboratory.
(14) Fabricat ion of s tainless s teel collecting tank", dump
tank for flow mete r calibration loop, s ta inless
s teel Vessel for testing of CRDM in sodium, plugg
ing indicator for mobile purification loop for .Reactor
Engineering Laboratory.
(15) Fabricat ion of 400 mm thick M.S . shielding block,
and centrifugal extractor for Reprocessing Develop
ment Laboratory.
(16) Fabricat ion of broaching machine for Central Work
shop.
(17) Machining of die block for Nuclear Fuel Complex,
Hyderabad.
- 274 -
(18) Machining of r a i l for fuel machine works , machining
of reciprocating chiller and cover, machining of ra i l
support, machining of sealing bellows for Madras
Atomic Power Project .
In addition to the above works Central Workshop ca r
ried out the welding qualification t e s t s for procedure and electrode
qualification tes ts for FBTR. Different types of mater ia l testing
have been car r ied out like tensile tes t ing, hardness measurement ,
impact test ing at room tempera ture as well as at sub zero tem
pera tures for different units in RRC and MAPP.
16. 2 Electrification of Site
33 KV Central Switching Station equipments such as
33 k V oil circuit b r e a k e r s , 33 kV iso la tors , 20 MVA 33/11 kV
t r ans fo rmer s , 33 kV control panels etc. were installed and com
missioned. Power supply to RRC is being received from Tamil
Nadu Electr ici ty Board through 33 kV over head line running from
Tamil Nadu Electr ici ty Board sub station at MAPP to 33 W switch
yard at RRC. The over head line was installed and commissioned
during this yea r . 11 kV panels were installed and commissioned
to feed 11 kV" supply to various laborator ies through 11 !kV under
ground cables .
11 kV underground cables were laid from Central
Switching Station to Central Workship, Reprocessing Development
Laboratory, Centralised Waste Management Faci l i ty , Engineering
Hal ls , Fas t Breeder Test Reactor temporary sub-station and also
to MAPP site for feeding MAPP and Township loads if required.
AH the above cables were tested for High Voltage with stand test
- 275 -
and then energised. The cables were jointed at every 200 me t res by
using 11 kV straight through joint boxes, since each drum length of
the cable will be about 200 m e t r e s .
33 kV end- joints for the 2 Nos . 10 MVA 33 kV/6 .6 kV
Fas t Breeder Test Reactor t r ans fo rmers were done and tes ted. Cons
truction power supply to Radio Chemistry Laboratory was provided.
16.3 Central Water Chilling Plant
Four 500 TR refr igerat ion machine consisting of chiller
compresso r , condenser , 3.3 .kV motor e tc . were received at site
and installed. Other equipments such as four chilled water pumps,
four cooling water pumps,, two air compressors etc . have been installed.
Ventilation equipment consiting of two supply blowers , two exhaust .
blowers and ducting etc. have been installed. Fabricat ion and installa
tion of chilled water piping, condenser water piping etc. have been
completed. Four induced draft cooling towers each consisting of two
cel ls with all associated equipment like fans, piping, valves etc. have
been installed. All these pipes have been hydraulically tested to with
stand a p r e s s u r e of 100 l b s / squa re inch,
One 12.5 tonne E . O . T . crane was erected in Central
Water Chilling Plant high bay and commissioned after duly testing
for 25% overload capacity.
Four control panels for remote control of re f r igera
tion machines were installed in the control room of Central Water
Chilling Plant. Two 1500 kVA 11 kV/433 V t rans fo rmers along
with M.V. switch gear have been installed and commissioned.
- 276 -
16.4 External Chilled Water Piping
Specifications were prepared and tenders floated for
laying external chilled water piping from Central Water Chilling Plant
to various laborator ies in RRC. The pipes have to be fabricated in
various s izes at site .by using 6 mm steel p la tes . The length of the
pipe to be fabricated and installed under this contract shall be about
4000 rae t r e s . All joints a re of welded type and shall pass radiography.
During the year under report contract has been awarded for the above
work and site fabrication works s tar ted. Evacuation to a depth of
1.5 me t r e s was car r ied out to a length of 250 me t r e s for laying
450 mm dia. pipes.
16.5. Laboratory Buildings
All internal electrification works for Reprocessing D
Development Laboratory and Materials Science Laboratory have been
completed. Works were in p rogress for a i r conditioning, ventilation
and communication sys tems for the var ious laborator ies .
- 277 -
ERRATA
LOCATION
Page
18
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25
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19
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250
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276
13
2
19
8
3
3
24
7
17
18
12
FOR
Pr i l iminary
std. cm /Sec.
110 to 120 MPa
500 MPa
2 0 / Um
2 - 4 ^
„ CNaH K = - - i
U Na(PH 2 ) 2
Tempera tures of
s tandarized
micro
Ven ugopal
spherol dizaticn
Karhikeyan
manochromator
0. 0/Ohm
18°
100 lbs / square inch
Reprocessing D
READ
Pre l iminary 3 / cm / s
11 to 12 MPa
50 MPa
20 urn
2 - 4 pm
" C NaH ,
Sa^H^
Tempera tures
standardized
micron
Venugopal
spheroidization
Karthikeyan
monochromator
0. 01 ohm
18 6
7 MPa
Reprocessing
