Hydrogen-tritium transfer in SFR Concepts
description
Transcript of Hydrogen-tritium transfer in SFR Concepts
Hydrogen-tritium Hydrogen-tritium transfertransfer
in SFR Conceptsin SFR Concepts
K. LIGER, T. GILARDITél : 33 (0)4 42 25 49 08
e-mail : [email protected]
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OUTLINESOUTLINES
• Theory of diffusion and mass transfer phenomena– Fick’s law, parameters, steady state...– Data’s for liquid Na and stainless steel: Sievert constants, permeation, diffusion – Permeation Na/Metal/Na and Na/Metal/gas– Equilibrium between Na and cover gas– Cold trap and cristalisation– Links between H and T transfers
• Mass transfer in a reactor System definition Pollution sources Modeling Estimation of the fluxes of Hydrogen and tritium
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General goal for tritium transfer estimationGeneral goal for tritium transfer estimation
• Estimate :– The distribution of H and T in the circuits and then the gaseous and liquid release of T as well as the
accumulation of T in the cold traps
• SO THAT:• During operation
– The release does not exceed release authorisation• During conception
– A suitable release limit authorisation could be asked
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Theory: Mass transfer through a wallTheory: Mass transfer through a wall
• Hydrogen permeation includes severall phenomena – Molecule dissociation at the interphase between metal and medium– Adsorption, Absorption– Diffusion in the metal– De-absorption, De-adsorption– Atoms combination
In general, mass transfer is controlled by diffusion (combination is the second predominant phenomena)
Hence, permeation can be represented by Fick’s law
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Theory of Diffusion : Fick ’s law Theory of Diffusion : Fick ’s law
• Équations de Fick - Fick’s law- Mass conservation’s law
• For a simple geometry
• E.g.: Evolution of concentration in a plan wall after a step of concentration from C = C2 to C1
t=infinite t t=0
C2 C2 C2
C1 C1 C1
o
x
j D C
div jC
t
0
j : fluxD : diffusivityC : concentratione : thickness
j DC
x
DC
x
C
t
2
2 0
e
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Steady state vs transient state ?Steady state vs transient state ?
• When steady state and transient meet each other…– Assumption : plan wall– Time to reach 99,99% of the steady state flow depends on:
• D, diffusivity of material (function of temperature and nature of the material) • e, thickness
tp does not depends on the concentration gradient
Time to reach 98,5% of the steady state flow: tp /2
p
e
D
2
Over the lifespan of a reactor, steady state can be assumed!
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Theory: Diffusion depends on…Theory: Diffusion depends on…
• Nature of material: Austenic steel versurs ferritic steel, ....– factor 100 for D at 250°C, and only 10 at 500°C
• Temperature:– D = A exp( -E / T(K) ) , m² /s– SS316 : factor 105 between room temperature and 500°C
• Surface state : Oxidised layer is a permeation barrier
• Hydrogen trapped in the metallic structure
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Diffusion : Hydrogen/tritium trapped in metallic structureDiffusion : Hydrogen/tritium trapped in metallic structure
• Gaseous adsorption on metallic surface– external on surface– internal on small fissuration and defect structure
• In the matrix– Impurities– Grain boundaries– dislocations...
• Some of these mechanisms are irreversibles– E.g.: during heating of metal in a vacuum oven, hydrogen release is observed up to melting temperature
• Behaviour of T similar to 1H, but isotopic exchange may modify macroscopic behaviour of T
– In presence of hydrogen trapped in the structure:• Shorter transient state for T diffusion • Lower diffusion flux under steady state
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Theory: H/T equilibrium between cover gaz and NaTheory: H/T equilibrium between cover gaz and Na Sievert constantSievert constant
• Hydrogen equilibrium between Na (liquid or solid) and the cover gas
P. = H2H
NaSHK
)(gas2
H 2
1 Na
H
NasT
NasH KK 73,1
)(gas2
T 2
1 TNa
P. = T2T
NaSTK
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Theory: equilibrium between gas and metal Theory: equilibrium between gas and metal Sievert constantSievert constant
steel
ST
steel
SHKK
P. = H2H
AcSHK )(gazeux
2H 2
1 Hmetal in
)(gazeux2
T 21 T
metal in
P. = T2T
AcSTK
• Hydrogen equilibrium between metal and the cover gas
• Similar solubility of H and T in steel
• Diffusion depends on atomic mass
• Hence, diffusion is « easier » for H
1
3steel
T
steelH
D
D
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Solubility in metal : Sievert constant Solubility in metal : Sievert constant
E.g.: SS316, mol(H)/m3(acier)/pa1/2
– KTISON (1983) = 0,9123 exp( -1352,1 / T(K) )– KFORCEY (1988) = 0,9424 exp( -2229 / T(K) )– KGRANT (1988) = 2,2191 exp( -1890 / T(K) )
0
0,05
0,1
0,15
0,2
0,25
200 250 300 350 400 450 500 550 600T, °C
mol
(H)/m
3/P
a1/2
Forcey [7]Tison [6]Grant [8]
DFORCEY (1988) = 3,82 10-7 exp( -5472,4 / T(K) ) , m² /s
1,E-15
1,E-14
1,E-13
1,E-12
1,E-11
1,E-10
1,E-09
1,E-08
25
150
250
350
450
550
T, °C
D, m
²/s
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Theory: Diffusion through a wall immersed in NaTheory: Diffusion through a wall immersed in Na
Plan wall
C Na1 = SH
Na1K P and C Na
2 = SHNa
2K P
Cac1 = SH
ac1K P and Cac
2 = SHac
2K P
then 1ac SH
ac
SHNa 1
NaCK
KC and 2
ac SHac
SHNa 2
NaCK
KC
Fick’s law :
= DA
eC Cac ac
1 2 ( C in at/m3)
CCK
K NaNaNa
SH
ac
SH
e
A = D 21 (C in at/m3)
then CCNaNa
e
A= PE 21
PE = D. = pe
. SHac
SHNa
SHNa
K
K K
C1Na
C2Na
C1ac
C2ac
e
Na
Na
where : at/s PE : kg/m/s
CiNa : at/kg
: kg/m3 KSH
Na, KSHac : at/m3/Pa1/2
Similar equations for T
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Theory: Diffusion through a wall immersed in Na and gasTheory: Diffusion through a wall immersed in Na and gas
1ac SH
ac
SHNa 1
NaCK
KC
2ac
2C P KSHac
= DA
eK
KC K P
SHac
SHNa 1
NaSHNa
2 (C in at/m3 ; P2 in Pa)
P.C
K
K2
NaSHNa
1Na
SH
ac
SH Ke
AD. =
... (C in at/kg)
with PE = D. = pe
.SHac
SHNa
SHNa
K
K K
and KU. C Pgas22 SH
NaK
thus = PEA
eC KU. C1
Na2gas
with C1Na: at/kg
C2gas : at/kg
M : kg/molP : Pa
C1
C2
C1ac
C2ac
e
gas
Na
Similar equations for T
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Theory: Diffusion through pipesTheory: Diffusion through pipes
• In that case, diffusion flux through the surface is:
2
2
1
1 2 1 2
Lrr
D C C DA
eC Cml
ln
rr1 r2o
A
L r rrr
ml 2 2 1
2
1
ln
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• Flux of hydrogen to the cold trap:
• Flux of Tritium to the cold trap:– Co-cristallisation of tritium with H
– Isotopic exchange and T decay neglected
)(3 trapcoldT
CCqf
5.0*
)(
trap cold T
s
CC
CC
Cold traps :Cold traps :
Cold trap efficiency:
Na
H
Na
T
trapcoldT
Na
H
Na
H C
CCCqf
)(3
0,01
0,1
1
10
100
1000
10000
100130
160190
220250
280310
340370
400430
460490
520550
580
Te m pe rature , °C
[O], ppm
[H], ppm
C*: Solubility of H in Na
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Theory: Isotopic exchange in gas phaseTheory: Isotopic exchange in gas phasehydrogen - tritiumhydrogen - tritium
• Isotopic exchange reaction:
• Equilibrium constant is:
H T HTgaz gaz gaz2 2 2( ) ( ) ( )
kP
P PHT
H T
2
2 2
Ln kT K
1 4966133
,( )
0
1
2
3
4
5
100 300 500 700T, °C
k
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Tritium transfer in a ReactorTritium transfer in a Reactor
1. Steady state calculation
2. Homogeneity of concentrations in the circuits
3. Isotopic exchange in cold traps neglected as well as T decay
4. Source of T: – In primary circuit:
• Ternary fission reactions• Control rod reactions• Activation of impurities: B, Li Estimation of the source on the base of Superphenix and Phenix past experience
5. Source of H:– In primary circuit: fission reactions. – In secondary circuit:
• Gaz in the ternary circuit: source = 0• Water in the ternary circuit
– Aqueous corrosion of GV– Thermal decomposition of N2H4 used in water to limit presence of O :
3 N2H4 = 2 NH3 + 2 N2 + 3 H2 for T>250°C Estimation of the source on the base of Superphenix and Phenix past experience
Assumptions:
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RURNa/Na
Ar
GV Turbine
I IIIII
RURNa/Air
PF I
BPR
~
Schematic view of the reactorsSchematic view of the reactors
Y - H2O
- He-N2
- SCO2
SPX:reference case
Improvement of the models for Tritium transfer in other SFR concepts
And for other fission reactors (EPR, HTR, VHTR…)
PF II
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SFR: Mass balanceSFR: Mass balance
• Diffusion through heat exchangers
• Diffusion through GV
• Diffusion through pipes and volumes
• Trapping in cold traps (for H in Na) / Sources in the circuits
• H exchange with covering gas
for Hydrogen:for Hydrogen:
• Diffusion through heat exchangers
• Diffusion through GV
• Diffusion through pipes and volumes
• Trapping in cold traps (for T in Na) / Sources in the circuits
• H/T exchange with covering gas
for Tritium:for Tritium:
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Localisation of exchange in the different conceptsLocalisation of exchange in the different concepts
Localisation T flux% H flux % Primary cold traps 41 46 Secondary cold traps 19 23 GV 3 7 Intermediate heat exchanger 26 9 Pipes and volumes 7 10
Localisation T flux% H flux % Primary cold traps 28 6 Secondary cold traps 35 89 GV Intermediate heat exchanger 36 5 Pipes and volumes
SFR Na/Na/H2O
SFR Na/Na/SCO2
Localisation T flux% H flux % Primary cold traps 31 35 Secondary cold traps 14 16 GV 30 30 Intermediate heat exchanger 19 8 Pipes and volumes 3 7
SFR Na/Na/He-N2
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Concepts comparisonConcepts comparison
SFR Na/Na/H2O, Na/Na/SCO2, Na/Na/He-N2
• Presence of H2O in the ternary circuit leads to a source of H, which is benefit to reduce gaseous leakage:
• Release of T for Na/Na/H2O: 65 kBq/s• Release of T for other concepts: nearly 1200 kBq/s
• Presence of:• secondary cold traps of great importance for Na/Na/H2O concept• primary cold traps of great importance for other concepts
• Permeation through GV:• is of great importance for Na/Na/H20 concept. Great PE lowers gaseous release• has no effect for other concepts
• Addition of secondary hydrogen source minimises T release
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Conclusion ...Conclusion ...
– Diffusion
– T release depends on the concept– Importance of cold traps– Importance of Hydrogen source– Ways of limitation of diffusion: nature of metal, oxydised layer, thickness, temperatures, aeras– Modeling partially validated on Phenix and Superphenix former results
– Modeling Improvement needed: • Colds traps modeling should be improved• Transient state should be implemented• Measurement of H/T diffusivity through metals
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ReferencesReferences
[1] Paul TISONInfluence de l’hydrogène sur le comportement des métaux.Rapport CEA-R-5240 ; Thèse présentée à l’université Paris 6 le 9 Juin 1983
[2] K.S. FORCEY ; D.K. ROSS ; J.C.B. SIMPSON ;D.S. EVANSHydrogen transport and solubility in 316L and 1.4914 steels for fusion reactor applications.Journal of Nuclear Materials 160 (1988), North Holland, Amsterdam.
[3] D.M.GRANT ;D.L. CUMMINGS and D.A. BLACKBURNHydrogen in 316 steel ; diffusion, permeation and surface reaction.Journal of Nuclear Materials 152 (1988), North Holland, Amsterdam.