AE-91

0 \

The Energy Variation of the

Sensitivity of a Polyethylene

Moderated BF3 Proportional Counter

R Fräki, M. Leimdörfer and S. Malmskog

AKTIEBOLAGET ATOMENERGISTOCKHOLM SWEDEN 1962

AE-91

THE ENERGY VARIATION OF THE SENSITIVITY OF A POLY-

ETHYLENE MODERATED BF, PROPORTIONAL COUNTER.

R. Fraki, M. Leimdörfer and S. Malmskog

Summary;

The variation with neutron energy of the sensitivity of a poly-

ethylene moderated boron counter has been investigated experimen-

tally at 2. 3 MeV, 550 keV, 210 keV, U0 keV, 340 eV and 5 eV,

and theoretically by the multigroup diffusion method in the same

range. Different moderator thicknesses up to ? 0 cm were con-

sidered*

Results show good agreement between experimental and theo-

retical sensitivities for the keV and MeV energies, while a discre-

pancy of the order of a factor 2 at the most is obtained in the eV

region.

Printed and distributed in November 1962

LIST OF CONTENTS

Page

1. Introduction 3

2. Experiments 3

3. Calculations 7

4. Discussion of results 10

References 1 1

Figures 12

- 3 -

1, Introduction»

By surrounding a boron counter with a moderating medium, its

initial, very low sensitivity for fast and intermediate energy neutrons

can be considerably increased.

This report gives results of an experimental investigation of the

variation of counter sensitivity with energy in the region 5 eV - 3 MeV

at varying thicknesses of polyethylene cladding» A method for obtaining

theoretical prodictions of the sensitivity is presented.

An experimental examination of the counter sensitivity was per-

formed in the keV and MeV regions using accelerator neutrons and in

the eV region with a chopper-time-of-flight analysis,

2j_1» Accelerator measurements.

Neutrons in the energy range 100 - 600 keV were obtained by7

the Li (p, n)-reaction* The protons were accelerated in the 5O 5 MeV

van de Graaff generator at Studsvik» The vertical proton current from

the accelerator was bent in. a 90 ̂ magnet to hit the lithium target 10 m

away,, The latter consists of a wobble target with a backing of tantalum on

which a thin lithium metal layer was obtained by evaporation, A target

thickness of 20 keV for 2 MeV protons was used. As a measure of the

proton energy the current through the analysing magnet was used and

calibration was rria.de against the Li-re.sona.nce at 1, 88Z MeV. The

accelerator potential was kept constant to within 0e 1 % by corona sta-

bilization»

The geometry of this experiment is shown in fig» 1, The detector

consists of an array of six counter tubes, placed between two identical

slabs of polyethylene. This arrangement was expected to give a fair

simulation of the idealized calculation geometry, viz, a three-medium

system, of extended slabs in one-dimensional plane geometry.

~ 4 -

The counters \vc5re made of electrolytic copper, each having a

diameter of 30 mm and a sensitive length of 200 mm. The counting

gas was 600 mm Ilg boron enriched to 95 % in B . This detector

was pJaced at a distance of 260 cm from the Iå-target and at an angle

of 24 with respect to the direction of the incident protons. Ptire

polyethylene sheets with, dimensions 600 x 380 x 6 mm were used.

The measurements were performed by adding polyethylene sheets

from 0 up to a total thickness of 30 mm symmetrically in front of

and behind the boron counter, The neutron flux incident on the po-

lyethylene was monitored with a proportional counter filled with

hydrogen to a pressure of 740 mm Ilg. The (n, p)-scattering causes

a proton recoil spectrum, from which the absolute neutron flux in

the proportional counter can be determined using the method worked

out by Skyrme et al. (ref. ?).

In Ihe first run on every new neutron energy the absolute neu-

tron flux was measured with a long-counter. The other Qux deter-

minations at the same neutron energy were made relative to the

long-counter.

A neutron energy of 2. 3 MeV was achieved by the D(d, n)He -

reaction. The incident deuteron energy was 200 keV and the boron

counters were placed at an angle of 1 1 0 with the deuteron beam.. The

distance to the target, a 50 keV deuteron layer on a zirconium backing,

was 48 cm. The neutron flux was this time meas\ired with a propor-

tional counter filled with methane to a pressure of 1860 mm Hg to re-

duce the range of the recoiling protons. The experimental techniques

and interpretation were identical with those described above»

2. 2, Chopper experiments

Sensitivity measurements in the eV-region were carried out with

the fast chopper installed at the Swedish reactor Rl in Stockholm. A

thorough description of the chopper facility is given by Johansson et al0

(ref. 2), The neutrons to the chopper are taken from the central reactor

channel. The flight path is 21. 16 m. A schematical view of the set-up

- 5 -

is given in fig0 2. These measurements were performed partly with

a single counter tube placed according to fig, 3, partly with the same

counter battery as was used in the accelerator measurements (fig» 1).

This permitted a comparison to be made between results for the two

geometries (cylinder and plane).

The counter sensitivity was obtained at 5 eV and 340 eV accor-

ding to the following principle; Neutrons passing the chopper were

filtered through gold and manganese foils and a time-of-flight analy-

sis was made of the output from the boron counter givint well-recog-

nizeable resonance dips.

It is expected that the relative ordinates at corresponding flight

times will make a good measure of the variation of the counter sen-

sitivity with moderator thickness. An absolute value is then obtained

by inserting the easily calculated (from cross-section and volume data)

sensitivity of the bare counter. The relative heights of the curves were

read off at corresponding times- of -flight away from the dip to prevent

uncertainties due to the steep descent in the resonance dipo

Another way of determining the relative efficiency would be to

compare the total number of counts "lost" by the detector due to re-

sonance absorption by integrating the area represented by the dip,

a quantity which can be related to the resonance integral. This method

was also applied, but it gave a larger spread of the results along the

curve of best fit than that indicated above, because of the difficulty of

determining the area, acctzrately.

2.2. 1. Chopper measurements with a single boron tube.

The detector, being analyzed, was a boron counter with a dia-

meter of 40 mm and a sensitive length of 410 mm, It was filled with

600 mm Hg BF, enriched in B to 95 %. The counter was screened2

with boron-paraffin so that only an area of 35 x 400 mm was exposedto the neutron beam (fig. 3), The moderator material consisted of

s. 1 mm thick polyotliylene layer, which, could be rolled around the

counter. The detector pulses were fed into a time analyzer with

100 channels. The channel width could be varied 5a steps from 2 to

100 |j.s and the channels could "be distributed in two groups with a

time interval in b etwee.a.

During the experiment the rotor speed was constant and equal

to 1920 rpm, giving neutron trursts with a time distance of 3920 u,s

and a half width of 10, 0 JAS. The channel width was chosen to 5 fxs.

This makes it possible to ineasu.ee neutron energies between 1 and

1000 eV. The time analyser was adjusted .so that neutrons arriving

during the first 300 p.s were sorted in intervals of 5 jas in the first

60 channels» The next 35 channels register neutrons with flight times

between 600 and 775 j.'.s, The last 5 channels were used for background

measurements, To get an energy-calibration, a 1 0 JJ. gold foil and a

100 [A manganese foil were inserted just above the rotor» These foils

give resonance absorption at energies 4,9 eV and 340 eV« In this way

the neutron energy spectra from the boron detector with 4 different

thicknesses of polyethylene were measured, natnely 2, 4, 6 and 9 mm.

Results are shown in figs, 4 and 58 The dip below the 5 eV re-

sonance in gold (fig, 4) moves slowly toward longer flight times with

increasing moderator thickness, indicating the slight time delay in

the moderator due to slowing-down before detection.

2, 2. 2. Chopper measurements with a battery of boron tubes

The detector battery used in this experiment is the one described

under 2. 1. (fig, 1) and the same principle of applying the moderator

plates was used. Measurements were performed with polyethylene

thicknesses from 0, 5 cm up to 3» 5 cm on each side, and results are

shown in fig, 6 a:ad 7»

- 7 -

3. Calculations,

To permit extrapolation; of the experimental results a multigroup

diffusion calculation was performed applying the Mercury programme

RASP developed by S. Linde (ref. 3). The group equations (with, it is

hoped, self-explanatory notation) can be written in the form

= 0 i = 1 (highest-energy group)

D. co. + 2 . . = 0

where the group-absorption cross-section

G

2. = 2 , . + \ 2.i abs, i i_j i—»k,

k=i+l

G = total number of groups

The calculation geometry was 1-dimensional plane as shown in

fig, 1. The arrangement of energy groups for the run with incident

neutrons at 3 MeV is displayed in Table 1 (constants for other runs

are obtained by deletion of the necessary number of groups). The group

structure is taken from ref, 4, as the preliminary test calculations

were based upon group constants taken from that reference» Parame-

ters 2 , . for all groups and D. for groups 2-14 were obtained for

polyethylene, (CH~) 0, 92 g/cm , from the programme MENDIP,c» n

making use of its data library (ref. 5), giving

D.i

E.i

dE3 2 E

tr

E .

dE

t r C el, C Wel, H

I"./% j o

• J \/ "TT ~E"

E.labs, i abs _,

Hi.

•where the superscript indicates the 2200 m/s values.

The D. for groups 15-18 for polyethylene were calculated byhand using a cr ., given in the paper by Krieger and Nelkin (ref« 6)

e«s.$ xx **taking Into account chemical binding effects.

The energy group containing the source was considered to havezero energy width and the spatial attenuation of the flux was made to

follow a strictly exponential law with a relaxation length equal to•™ i 1 1Sf f for the source energy» By setting D- = «—» » ( in the group"°" { 1 tot

equation for the virgin flux the wanted solution was obtained automati-cally from the multigroiip diffusion programme.

The transfer cross-sections S. . for polyethylene were calcu-lated on the assumption that slowing-down between groups was en-tirely due to hydrogen elastic collisions, a hypothesis which shouldbe very well justified fox such a hydrogen-rich material.

E.

J'E j+!

H el« I

E.J

E i ~ ]

/

MA4A 1

dEE

I

A « atonaic weight of I'noderator nuclei»

- 9

An exception was made for the transfer from the source group

(with energy width equal to 0} in which case carbon collisions were

assumed to degrade the virgin neutrons to the group below. The effect

of chemical binding in the lowest energy groups was considered by

using an equivalent proton mass (ref. 6) in the formula for 2. . and

by increasing the magnitude of cr (ref. 6).

Multigroup parameters for the counter gas were obtained from

different literature sources, <r for F was taken from ANL-5800

(ref. 7, p0 385), cr for B t 0 from LAMS 2255 (ref. 4) and cr , for

B from WAPD-TM-224 (ref. 8).

Group constants for the 3 MeV case are shown in Table II

(groups 2-18) whereas constants for virgin groxrps are given in

Table III for all cases treated.

External boundary conditions were given by assigning values

to the coefficients a,., a?» a., in the equation

t

a. Dcp + a? cp -f a, = 0

For the source group the values a. = 0, a, ~ 1, a~ = - 1 were

given for the source boundary, thus fixing the incident current as well

as flux to 1 for correct normalization. The external boundary opposite

to the source side was characterized by the conditions a. = 1, a? = T,

a., = 0, resulting in a strictly exponential attenuation of the virgin neu-

trons of the source group.

For energy groups other than the source group the conventional

transport theory black-boundary condition

= - 2. 13 D.

- 10 -

was applied at both sides. The boundary constants were thus

a.. - 2» 1 3, i\y •- - 1 , a, •- 0 for the surface adjacent to the source and

a. - 2. 13, <i_ - 1, u.> •= 0 for the other surface.

4. Discussion of results.

Mulligroup calculations were performed with source energies

at 8,315 cV, 454 c V, 17 keV, 0.1 MeV, 0.4 MeV, 1.4MeV, and

3 MoV and moderator thicknesses 0.5, 1,0, 1.5, 2,0, 2.5, 3.0, 3.5,

5» 0, and 1 0, 0 {on each side of the sensitive volume). The sensitivity-

was then obtained by adding the products of fkix, sensitive volume, and

effective (n, a) cross-section over all energy groups. The calculation

results arc* displaced m fig, 8 and together with experimental values

in figs. 9-14.

Hie agreement-between theory and experiment in magnitude as

well as in shape seems to be fairly well established in the "accelerator"

region (no mutual normalization has been performed).

The results of the chopper experiments show good relative agree-

ment with the theoretical predictions at 4.9 cV source energy while the

magnitudes are a factor 1,7 higher than predicted (fig. 9), at 340 eV

source energy the eoi* responding error factor is not constant, but

varies between 1 and 2. 1 (fig. 10). We observe that the difference in

geometry when using a single counter tube or a battery does not affect

the sensitivity in the cases investigated.

- It -

References.

1) SKYR ME T H R , TUNNICJLIFFE P R and WARD A GA Proportional Counter for Neutron Fiux Measurements inthe Energy Range 0» 1 to 1 MeV.

'" Rev. Scio Instr» 23 (1952) p, 204.

2) JOHANSSON E, LAMPA E and SJÖSTRAND N GA Fast Chopper and its Use in the Measurement of NeutronSpectraArkiv för fysik _1_8 (I960) p. 513

3) LINDE SThe Multigroup Neutron Diffusion Equations/1 Space Dimension»1960 (AE-35)

"4) MILLS C BNeutron Cross Sections for Fast and Intermediate Nuclear Reactors1960 (LAMS-2255)

5) SYNGE M J"MENDIP": a Digital Programme for Calculating Neutron DiffusionParameters»1960. (SWP/P. 67) + 1961 (Supplement 1).

6) KRIEGER T J and NEJLKIN M SSlow-Neutron-Scattering by MoleculesPhys. Rev. J_06 (1957) p. 290.

7) Reactor Physics Constants, 1958. (ANL-5800)

8) HENRY A F54 Group Library for P~ 1 Programs. 1 960. (WAPD--TM-224).

RF, ML and SM/EL

Table IArrangement of Groups

Group

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Energy Range

3-1.4 MeV

1.4-0.9

0.9-0.4

0.4-0.1 »"

100-17 keV

1 7 - 3

3 - 0.454 "

454 - 61.44 eV

61.44 - 22.60 "

22.60- 8.315 »

8.315- 3.059 "

3.059 - 1.1256"

1.1256 - 0.4141 ••

0.4141 - 0.1523"

0.1523 - 0.0561"

0.0561 - 0.0252"

£ 0.0252

Lethargy Range

1.204-1.966

1.966-2.408

2.408- 3.219

3.219- 4.605

4.605- 6.377

6.377- 8

8 -10

10-12

12-13

13-14

14-15

15-16

16-17

17-18

18-19

19-19.8

£19.8

T a b l e I i

M u l t i g r o u p P a r a m e t e r s ( o r G r o u p s ä - 1 8 l o v 3 M e V r u n .

G r o u p

2

3

4

5

6

7

8

9

10

I I

12

13

14

15

16

17

18

D j [ c m )

2 . 4 2

1 . 6 9

1 . 2 5

0 . 8 2 4

0 . 5 7 0

0 . 4 8 5

0 . 4 6 9

0 . 4 6 8

0 . 4 6 8

0 . 4 6 7

0 . 4 6 4

0 . 4 6 1

0 . 4 4 7

0 . 3 7 7

0 . 1 6 8

0 . 1 3 0

0 . 1 2 0

S ( c m " )

2 . 9 5 - 1 0 " 6

3 . 9 7 - 1 0 " 6

5 . 4 5 - 1 0 " f c

9 - 5 7 - 1 0 " 6

2 . 1 3 - 1 0 " 5

5 . 1 2 - 1 0 " 3

1 . 2 7 - 1 0 " *

3 . 3 8 - 1 0 " 4

6 . 9 3 - 1 0 " 4

1 . 1 4 - 1 0 " 3

1 . 8 7 ' i O " 3

3 . 1 1 • 1 0 " 3

5 . 1 3 - 1 0 " 3

8 . 4 5 - 1 0 " 3

1 . 3 9 - 1 0 " 3

2 . 1 8 - 1 0 " 2

2 . 3 3 - 1 0 " 2

Si —K

6 . 6 0 -

1 . 7 6 -

2 . 3 9 -

3 . 3 9 -

5 . 0 2 -

6 . 6 8 -

5 . 9 6 "

4 . 3 8 -

6 . 6 0 -

6 . 6 0 -

6 . 6 ! '

6 . 6 1 •

6 . 9 2 -

1 . 0 2 -

1 . 5 8 7

3 . 0 0 5

P c

+ 1

1 0 " 2

1 0 " '

lo"1

IO- 1

I D " '

I D " 1

lo"1

( 0 " '

1 0 " '

l O " 1

1 0 " '

to"1

I D " 1

io"1

-

1

55

5.

8.

5 .

5 .

9 .

1 .

5 .

1.

2 .

2

2 .

2 .

2,

2.

1.

y c t h y

3 3 - I O " 2

5 3 - t O " 2

9 3 - I 0 " 2

4 5 - 1 0 " 2

0 9 - 1 0 ~ 2

0 0 • 1 0 " 1

7 3 - 1 0 " 2

5 9 - I O " 1

3 2 - 1 0 " '

3 2 - 1 0 " 1

3 2 - I 0 " 1

3 2 - 1 0 " '

4 4 - 1 0 ~ l

3 0 - 1 0 " 2

4 1 • 1 0 " '

-

o

S.

3 .

2 .

9.9.t.9

2 .

5 .

3.

8 .

8 .

8.

7 .

n c

—*

20

35

95

95

40

95

11

85

53

53

53

53

82

i+3

• l o " 2

• l O " 2

• 1 0 " 3

• i o - 3

• l O " 2

• 1 0 " 3

• l o " 2

• I T 2

• 1 0 " 2

. io- 2

M O " 2

• t o " 2

• l o " 2

0

-

-

2i

8.

3.

1.

1.

1.

3.

7 .

2 .

3 .

3 .

3 .

2 .

6.

—»

85

99

82

52

38

66

82

15

14

14

14

75

40

i+4

M O " 3

• to"3

• l o " 3

• i o - 3

• 1 0 " 3

• 1 0 " 3

- l o " 3

• i o - 2

• I D " 2

• 1 0 " 2

• 1 0 " 2

• i o - 2

• l o " 2

-

-

1

1.

7.

2 .

1.

5 .

t

2 .

7.

1.

I .

1.

2 .

- »

49

23

80

51

06

34

85

90

16

15

01

24

1+5

• i o - 3

. 1 0 " *

. i o - *

• 1 0 " 4

- l o ' 4

• i o - 3

i o - 3

- . O " 3

• i o - 2

• l O " 2

• lo"2

• 10'2

-

-

-

-

z.1 —•

0

0

• 0

0

0

0

0

0

4 . 2 7 •

3 . 7 i -

8 . 2 2 -

-

-

-

-

-

+6

l o " 3

to"3

J O " 3

D l

1 . 5 9 - 1 0 3

1 . 3 2 - I O 3

8 . 2 6 - I O 2

7 . 8 7 - S O 2

5 . 0 3 . 1 0 2

i . 0 1 • I O 3

7 . 8 1 • I O 2

1 . 7 8 - I O 2

2 . 2 9 - 1 0 2

1 . 6 8 - I O 2

1 . 1 7 • 1 0 2

6 . 9 0 - 1 0 l

4 . 6 5 - I O 1

2 . 8 7 - I O 1

1 . 8 1 • I O 1

1 . 2 5 • 1 0 1

1 . 3 6 ' I 0 1

C o u n t e r G a s

4 .

4 .

8.

2 .

6.t.3 .

8.

1.

3 .

5 .

8.

1.

2 .

3 .

5 .

i

Ei

6 •

0 •

5 •

2 6 -

0 2 -

3 5 -

3 8 -

8 4 -

8 8 -

6 0 -

0 8 -

2 8 -

4 3 -

26 -

7 6 '

9 2 -

34 -

1 0 " b

1 0 " f c

1 0 " 6

<o-5

J O " 5

io-4

l O " 4

l o " 4

•a

1 0 "

1 0 " 3

1 0 " 3

1 0 " 3

io"2

i o - 2

1 0 " 2

to"2

i o " 2

Bi

2 .

3

4

4

6

2

2

2

3

3

3

3

3

3

3

3

- • i

5 8 -

8 6 -

2 4 -

CO-

7 2 -

9 6 -

B2-

8 2 •

. 4 2 -

. 4 2 -

. 4 2 -

. 4 2 -

. 4 2 -

. 4 2 -

4 2 -

4 2 '

+ 1

lo"5

1 0 " S

lo"5

to"5

io-5

io-5

• O " 5

lo"5

lo"5

1 0 " 5

1 0 " 5

io-5

1 0 " S

io-5

lo"5

l O " 5

Table IEMultigroup Parameters for Virgin Groups.

EnergyPolyethylene

* • l

Counter gas

3 MeV

U "

U «

0.1 ..

17 keV

45i eV

8.315eV

2.37 10"

3.59-10"

6.95-id

1.18 10

1.65

1.77-10

1.77

4 22-10

2.79 • 10°

1.U • 10°

847-10'

6.06-10'

5.65-10'

5.65-10'

1.53 • 10"1

1.83 • 10'1

557-ID'1

1.01 -10°

1.39 10°

1.55 -10°

1.19 -10°

3.05-10'

9.90-10'

,-2 305-10"" 1.82 -10" 5.05- 1.66-10"'-2 ^

1.15-10

1.40 -10'

2.19 10'

1.35-10"'

3.67-10"

5.82-10" i 1 63 10"'

1.94-1Ö"'! 3.52-10-3

2.76 • 10"

5.44-10"

2.50-10"2| 4.0 3-10" 4.00 • 10'

218-10"

5.38 -10"

129 -10'

4.98' 1C"2

1.36-10'1

3.37-10"' 3.33-10" , 123 -10"

1.83 -10"2 6.72 10"3

3.54 -10'

4.98 -10 1.83-10",-28.70 -10"

4.40 -1O'

6.02-103 124-10"'

4 .59-10 3 l i .54 ' ia '

186-103 i 4.64-10"4

7.75-10' 1.25 1CT

2.82-103.:258-10"'

1.15-103j 2.86-10"'

2 27-102 2.80-10"'

t-- Moocrotor Thicknesslengths \n

Real ond Idealized Geometries for the Plane Cases.

Y':

Setuc- -flight

033

(Distances in mm)

Fig.3 Set-up for Chopper Experimentsin Cylindrical Geometry.

4000 -

3000-

2000

1000 -

60 70 80 90 100Channel Number

Fig4 Results of Chopper Measurementswith Au Filter(Cylindrical Geometry).

6000

5000

4000

3000

2000

1000

\ rig.;' Results of C P̂P*

i Mn F'lvcr (CylindricalGeometry}

/v.

10 20 30 40 50Channel Number

Chcinnel Mumoer

Fig.8 Results of Chopper Measurementswith Au Filter (Plane Geometry).

Moderatorthicknessesih mm' - 35» • 3 0« • 70

0 10 20 30 40Channel Number

Fig.7 Results of Chopper Measurementswith Mn Filter (Plane Geometry).

I I ! I I I11] I r i T u n l ! I M i l l ! I I M i l l

C p S / n / cm<

60

Fig.8 Counter Sensitivity Versus Neutron Energyat Various Moderator Thicknesses (Theoretical).(Sensitive Volume Normalized to 766cm)

Moderator ..Thicknesses

in mm

Without Moderator

i i i 11 ml i

Neutron Energy (MeV)

10'

1<f

1Ö3

m Cylindncof G*omstry

Th*ar<aticat Curve.

i 2 . 3Moderator Thickness in cm

Fig.9 Sensitivity of Moderated SR-Counter'. at 4.9 eV Versus Moderator Thickness

(Sensitive Volume 766 cm3)

Chopper Wtosuwrontsm Ptane Geometry

10°

o

Chopper Me<l<!urotnerfein Cybndricat Geometry

Theoretical Curve

1 2 3Moderator Thickness in cm

Ftg.10 Sensitivity of Moderated 8F3-Counierat 340 sV Versus Moderator Thickness(Sensitive Volume 766 cm3!

10'

10'

10'

10'

icro

Accelerator Measurements

Theoretical Curve

1 2 3Moderator Thickness in cm

Fig 11 Sensitivity of Moderated BF3-Counterat 0.11 MeV Versus Moderator Thickness(Sensitive Volume 766 cm3)

10'

10'

10'

Accelerator Meosurements

Theoretical Curve

1 2 3Moderator Thickness in cm

Fig.12 Sensitivity of Moderated BFa-Counterat 021 MeV Versus Moderator Thickness(Sensitive Volume 766 cm3)

\ /em's

10

10

Accelerator Measurements

Theoretical Curve

0 1 2 3Moderator Thickness in cm

Fig.13 Sensitivity of Moderated BF3"Counterat 0.55 MeV Versus Moderator Thickness(Sensitive Volume 766 cm3)

}102

101

10'

10"

10-

Accelerotor Measurements

Theoretical Curve

1 . 2 3Moderator Thickness in cm

Fig.14 Sensitivity of Moderated BF3-Counterat 2.3 MeV Versus Moderator Thickness(Sensitive Volume 766 cm3)

LIST OF PUBLISHED AE-REPORTS

1—19. (See the back cover of earlier reports.)

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

M.

45.

46.

47.

48.

49.

50.

51.

52.

53.

54.

55.

56.

57.

58.

59.

Optimisation of gas-cooled reactors with the aid of mathematical compu-ters. By P. H. Margen. 1959. 33 p. Sw. cr. 4:—.

The fast fission effect in a cylindrical fuel element. By I. Carlvik andB. Pershagen. 1959. 25 p. Sw. cr. 4:—.

The temperature coefficient of the resonance integral for uranium metaland oxide. By P. Blomberg, E. Hellstrond and S. Hörner. 1960. 14 p.Sw. cr. 4:—.

Definition of the diffusion constant in one-group theory. By N. G. Sjö-strand. 1960. 8 p. Sw. cr. 4j—.

Transmission of thermal neutrons through boral. By F. Åkerhielm. 2nd rev.ed. 1960. 15 p. Sw. cr. A:—.

A study of some temperature effects on the phonons in aluminium byuse of cold neutrons. By K.-E. Larsson. U. Dahlborg and S. Holmrya.1960. 21 p. Sw. cr. 4:—.

The effect of a diagonal control rod in a cylindrical reactor. By T. Nils-son and N. G. Sjöstrand. 1960. 4 p. Sw. cr. 4:—.

On the calculation of the fast fission factor. By B. Almgren. 1960. 22 p.Sw. cr. 6:—.

Research administration. A selected and annotated bibliography ofrecent literature. By E. Rhenman and S. Svensson. 2nd rev. ed. 1961. 57 p.Sw. cr. 6:—.

Some general requirements for irradiation experiments. By H. P. Myersand R. Skjöldebrand. 1960. 9 p. Sw. cr. 6:—.

Metallographic study of the isothermal transformation of beta phase inzircaloy-2. By G. Östberg. 1960. 47 p. Sw. cr. 6:—.

secondCalculation of the reactivity equivalence of control rods in thecharge of HBWR. By P. Weissgfas. 1961. 21 p. Sw. cr. 6:—.

Structure investigations of some beryllium materials. By I. Fäldl and G.Lagerberg. 1960. 15 p. Sw. cr. 6:—.

An emergency dosimeter for neutrons. By J. Braun and R. Nilsson. 1960.32 p. Sw. cr. 6:—.

Theoretical calculation of the effect on lattice parameters of emptyingthe coolant channels in a D2O-moderated and cooled natural uraniumreactor. By P. Weissglas. 1960. 20 p. Sw. cr. 6:—.

The mulligroup neutron diffusion equations/1 space, dimension. By 5.Linde. 1960. 41 p. Sw. cr. 6 : - .

Geochemical prospecting of a uraniferous bog deposit at Masugnsbyn,Northern Sweden. By G. Armands. 1961. 48 p. Sw. cr. 6:—.

Spectrophotometric determination of thorium in low grade minerals andores. By A.-L. Arnfelt and I. Edmundsson. 1960. 14 p. Sw. cr. 6:—.

Kinetics of pressurized water reactors with hot or cold moderators. ByO. Norinder. 1960. 24 p. Sw. cr. 6:—.

The dependence of the resonance on the Doppler effect. By J. Rosén.1960. 19 p. Sw. cr. 6:—.Measurements of the fast fission factor IE) in UOj-elements. By O. Ny-lund. 1961. Sw. cr. 6 : - .

Hand monitor for simultaneous measurement of alpha and beta conta-mination. By I. D. Andersson, J. Braun and B. Söderlund. 2nd rev. ed.\%\. Sw. ct. 6-.—.

Measurement of radioactivity in the human body. By I. O. Anderssonand I. Nilsson. 1961. 16 p. Sw. cr. 6:—.

The magnetisation of MnB and its variation with temperature. By N.Lundquist and H. P. Myers. 1960. 19 p. Sw. cr. 6:—.

An experimental study of the scattering of slow neutrons from H2O andD2O. By K. E. Larsson, S. Holmryd and K. Otnes. 1960. 29 p. Sw. cr. 6:—.

The resonance integral of thorium metal rods. By E. Hellstrand and. J.Weitman. 1961. 32 p. Sw. cr. 6:—.

Pressure tube and pressure vessels reactors; certain comparisons. By P,H. Margen, P. E. Ahlström and B. Pershagen. 1961. 42 p. Sw. cr. 6:—.

Phase transformations in a uranium-zirconium alloy containing 2 weightper cent zirconium. By G. Lagerberg. 1961. 39 p. Sw. cr. 6:—.

Activation analysis of aluminium. By D. Brune. 1961. 8 p. Sw. cr. 6:—.

Thermo-technical data for D2O. By E. Axblom. 1961. 14 p. Sw. cr. 6:—.

Neutron damage in steels containing small amounts of boron. By H. P.Myers. W61. 23 p. Sw. cr. 6:—.

A chemical eight group separation method for routine use in gammaspectrometric analysis. I. Ion exchange experiments. By K. Samsahl.1961. 13 p. Sw. cr. 6:—.The Swedish zero power reactor R0. By Olof Landergård, Kaj Cavallinand Georg Jonsson. 1961. 31 p. Sw. cr. 6:—.

A chemical eight group separation method for routine use in gammaspectrometric analysis. I I . Detailed analytical schema. By K. Samsahl.18 p. 1961. Sw. cr. 6:—.

Heterogeneous two-group diffusion theory for a finite cylindrical reactor.By Alf Jonsson and Göran Näslund. 1961. 20 p. Sw. cr. 6:—.

Q-values for (n, p) and (n, a ) reactions. By J. Konijn. 1961. 29 p. Sw. cr.6:—.

Studies of the effective total and resonance absorption cross sections forzircaloy 2 and zirconium. By E. Hellstrand, G. Lindahl and G. Lundgren.1961. 26 p. Sw. cr. 6:—.

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Determination of elements in normal and leukemic human whole blood 1by neutron activation analysis. By D. Brune, B. Frykberg, K. Samsahl andP. O, Wettet. 1961. \6 p. Sv«. « . 6-.—.

Comparative and absolute measurements of 11 inorganic constituents of38 human tooth samples with gamma-ray spectrometry. By K. Samsahland R. Söremark. 19 p. 1961. Sw. cr. 6:—.

A Monte Carlo sampling technique for multi-phonon processes. By ThureHögberg. 10 p. 1961. Sw. cr. 6:—.

Numerical integration of the transport equation for infinite homogeneousmedia. By Rune Håkansson. 1962. 15 p. Sw. cr. 6:—.

Modified Sucksmith balances for ferromagnetic and paramagnetic mea-surements. By N. Lundquist and H. P. Myers. 1962. 9 p. Sw. cr. 6:—.

Irradiation effects in strain aged pressure vessel steel. By M. Grounesand H. P. Myers. 1962. 8 p. Sw. cr. 6:—.

Critical and exponential experiments on 19-rod clusters (R3-fuel) in heavywater. By R. Persson, C-E. Wikdahl and Z. Zadw6rski. 1962. 34 p. Sw. cr.

On the calibration and accuracy of the Guinier camera for the deter-mination of inlerplanar spacings. By M. Möller. 1962. 21 p. Sw. cr. 6:—.

Quantitative determination of pole figures with a texture goniometer bythe reflection method. By M. Möller. 1962. 16 p. Sw. cr. 6:—.

An experimental study of pressure gradients for flow of boiling water ina vertical round duct. Part I. By K. M. Becker, G. Hernborg and M. Bode.1962. 46 p. Sw. cr. 6:—.An experimental study of pressure gradients for flow of boiling water ina vertical round duct. Part I I . By K. M. Becker, G. Hernborg and M. Bode.1962. 32 p. Sw. cr. 6:—.

The space-, time- and energy-distribution of neutrons from a pulsedplane source. By A. Claesson. 1962. 16 p. Sw. cr. 6:—.

One-group perturbation theory applied to substitution measurements withvoid. By R. Persson. 1962. 21 p. Sw. cr. 6:—.

Conversion factors. By A. Amberntson and S-E. Larsson 1962. 15 p. Sw.cr. 10:—.Burnout conditions for flow of boiling water in vertical rod clusters.By Kurt M. Becker 1962. 44 p. Sw. cr. 6:—.Two-group current-equivalent parameters for control rod cells. Autocodeprogramme CRCC. By O. Norinder and K. Nyman. 1962. 18 p. Sw. cr.6:-~".On the electronic structure of MnB. By N. Lundquist. 1962. 16 p. Sw. cr.6:—.The resonance absorption of uranium metal and oxide. By E. Hellstrandand G. Lundgren. 1962. 17 p. Sw. cr. 6:—.

Half-life measurements of «He, « N , » O , *>F, »Al , "Se"Konijn and S. Malmskog. 1962. 34 p. Sw. cr. 6:—.

and "°Ag. By J.

Progress report for period ending December 1961. Department for ReactorPhysics. 1962. 53 p. Sw. cr. 6:—.Investigation of the 800 keV peak in the gamma spectrum of SwedishLaplanders. By I. D . Andersson, I. Nilsson and K. Eckerstig. 1962. 8 p.Sw. cr. 6:—.The resonance integral of niobium. By E. Hellstrand and G. Lundgren.1962. 14 p. Sw. cr. 6:—.Some chemical group separations of radioactive trace elements. By K.Samsahl. 1962. 18 p. Sw. cr. 6:—.

Void measurement by the (y, n) reactions. By S. Z. Rouhani. 1962. 17 p.Sw. cr. 6:—.

Investigation of the pulse height distribution of boron trifluoride pro-portional counters. By I. O. Andersson and S. Malmskog. 1962. 16 p.Sw. cr. 6:—.An experimental study of pressure gradients for flow of boiling waterin vertical round ducts. (Part 3). By K. M. Becker, G. Hernborg and M.Bode. 1962. 29 p. Sw. cr. 6:—.

An experimental study of pressure gradients for flow of boiling waterin vertical round ducts. (Part 4). By K. M. Becker, G. Hernborg and M.Bode. 1962. 19 p. Sw. cr. 6 : - .

Measurements of burnout conditions for flow of boiling water in verticalround ducts. By K. M. Becker. 1962. 38 p. Sw. cr. 6:—.

Cross sections for neutron inelastic scattering and (n, 2n) processes. ByM. Leimdörfer, E. Bock and L. Arkeryd. 1962. 225 p. Sw. cr. 10:—.

On the solution of the neutron transport equation. By S. Depken. 1962.43 p. Sw. cr. 6:—.Swedish studies on irradiation effects in structural materials. By M.Grounes and H. P. Myers. 1962. 11 p. Sw. cr. 6:—.

The energy variation of the sensitivity of a polyethylene moderated BF3proportional counter. By R. Fräki, M. Leimdörfer and S. Malmskog. 1962.12 p. Sw. cr. 6:—.

Förteckning över publicerade AES-rapporter

1. Analys medelst gamma-spektrometri. Av Dag Brune. 1961. 10 s. Kr 6:—.

2. Bestrålningsförändringar och neutronalmosfär i reaktortryckfankar —några synpunkter. Av M. Grounes. 1962. 33 s. Kr 6:—.

Additional copies available at the library of AB Atomenergi, Sfudsvik, Nykö-ping, Sweden. Transparent microcards of the reports are obtainable throughthe International Documentation Center, Tumba, Sweden.

EOS-tryckerierna, Stockholm 1962