23 feb. 04 Direction de l’Energie Nucléaire 1 Wilfrid Farabolini Tritium Control A Major Issue for a Liquid Metal Blanket
Dec 21, 2015
23 feb. 04Direction de l’Energie Nucléaire 1Wilfrid Farabolini
Tritium Control
A Major Issue for a Liquid Metal Blanket
23 feb. 04Direction de l’Energie Nucléaire 2Wilfrid Farabolini
Schematic Fluids Circulation in the Reactor
JFWJ3
J5
Tritium extractionfrom LiPb
He purification
QHe
LiPb
He
MHe
QPbLi
J1
J2
J4
Blower
Steam generator
Secondary circuit
Blanket modules
LiPb purification
Pump
air purification
QPbLi
QHe
MLiPb
23 feb. 04Direction de l’Energie Nucléaire 3Wilfrid Farabolini
Analytical Model – Tritium Mass Balance Equations 1/2
LiPb HeJ1
J2 J4
J3 J5 J1 / J5 =140525
day/g385J1 • J1 : Production rate
LiPboutLiPb2 GCJ • J2 : Extraction from LiPb
LiPb : extractor efficiency for LiPbCout : Tritium output concentration in LiPb (mol m-3), GLiPb : LiPb flow rate (m3 s-1)
blanketave3 KCJ • J3 : Permeation towards He coolantCave : Tritium average concentration in LiPb (mol m-3)
Kblanket: Blanket permeation factor (m3 s-1)
HeHeHe4 GCJ • J4 : Extraction from He coolantGHe : He flow rate to detritiation unit (m3 s-1)
)LK(CJ SGSGHe5 ( J5 max = 1 g/year=27 Ci/day , ITER standard )
• J5 : Release to environmentLSG: Steam Generator leak flow (m3 s-1)
23 feb. 04Direction de l’Energie Nucléaire 4Wilfrid Farabolini
Analytical Model – Tritium Mass Balance Equations 2/2
321LiPb JJJt
M
543He JJJt
M
out
inLiPb C
C1
2
CCC outin
ave
LiPb
steelsteel
bblanket Ks
DKs
s
A
PRF
1K
• A, s : respectively wall surface (m2) and wall thickness (m). Need to be evaluated for complex structures (see below)
• Kssteel KsLiPb : Sievert constants (mol m-3 Pa-1/2), respectively in Eurofer and in LiPb• Dsteel Tritium diffusivity in Eurofer (m2 s-1)• PRFb is the Permeation Reduction Factor provided by permeation barrier (if any)
Stationary results (*) :
blanket
LiPb
13
KG
22
1
JJ
LiPb
LiPb
)LK(
G1
JJ
SGSG
HeHe
35
525140J
J
LK
G1
K
G
2
21
MAX,5
1
SGSG
He
blanket
LiPb He
LiPb
LiPb
* Thanks to Italo Ricapito (ENEA consultant) who initiated these computations
23 feb. 04Direction de l’Energie Nucléaire 5Wilfrid Farabolini
Computation of the Blanket Permeation Factor
LiPb
steelsteel
bblanket Ks
DKs
s
A
PRF
1K
Coating
Geometry
Materials and Temperature
Material factor : )TR
Eexp(X)T(X a
0
Geometrical factor :A
sCoating :
T concentration layering in LiPb :(not taken into account in this analytical model: convection)
23 feb. 04Direction de l’Energie Nucléaire 6Wilfrid Farabolini
Materials factor computation
• Significant permeation increase with temperature
• Uncertainties when averaging temperatures
Ks0(mol m-3 Pa-1/2)
Ea(J mol-1)
D0(m2 s-1)
Ea(J mol-1)
LiPb 1.25 10-3 1350 4.03 10-8 19500
Eurofer 1.02 10-1 23810 1.22 10-7 14470
23 feb. 04Direction de l’Energie Nucléaire 7Wilfrid Farabolini
Geometrical factor computation
• HCLL module is composed of many walls (FW, Stiffening grid, Cooling plates) where He circulates inside rectangular channels.
2b
2a2p
e
LN channels
• Permeation formula is relative to plain wall
• How to adapt it to the actual wall structure ?
• Lets A=2a.L.N (surface of He facing LiPb)
and s=e (minimum distance between He and LiPb).
s
NLa2Kgeom
(a, b, p, e) is the correction factor to be used to take into account the actual structure of the HCLL walls ?
23 feb. 04Direction de l’Energie Nucléaire 8Wilfrid Farabolini
Problem identical to heat transfer by conduction
• Temperature (K) tritium concentration (mol m-3)
• Thermal diffusivity (m2 s-1) D.Ks,w / Ks,PbLi material factor (m2 s-1)
• Heat flux (J s-1) tritium flow (mol s-1)
e
b
a p
LiPb
He
23 feb. 04Direction de l’Energie Nucléaire 9Wilfrid Farabolini
Correction Factor for Square Channels
• The thicker the ratio e/a the larger the correction factor
1,0
1,2
1,4
1,6
1,8
2,0
2,2
2,4
0 0,5 1 1,5 2p/a
e/a=0.5
e/a=1.0
e/a=1.5
e/a=2.0
23 feb. 04Direction de l’Energie Nucléaire 10Wilfrid Farabolini
Application to HCLL Walls• The three types of HCLL cooled walls have been modelled to
derive their correction factor
a (mm) b (mm) e (mm) p (mm)
First Wall(LiPb side)
7.0 6.5 4.0 2.0 1.24
Stiffening plates
5.0 1.5 2.5 0.5 1.09
Cooling plates
2.25 2.25 1.0 0.95 1.31
Back plate NA NA 30.0 NA 1
23 feb. 04Direction de l’Energie Nucléaire 11Wilfrid Farabolini
Geometrical Factor Results for the HCLL Module
LiPb facing He surface
(m2)
.A / s (m)
Percentage of total
permeation
First Wall (including side)
4.31 1336 1.06
Stiffening plates (including top and bottom)
37.06 16158 12.8
Cooling plates 82.94 108651 86.0
Back plate (plain) 4.0 133 0.1
• Module Kgeom= 126 278 m• 86 % of the permeation occurs through the cooling plates (and
even more if we consider their higher temperature)
23 feb. 04Direction de l’Energie Nucléaire 12Wilfrid Farabolini
Tritium flow towards He coolant (J3)• Kblanket = 0.89 / PRFb m3 s-1 (Tave = 480 °C, 260 modules)
• LiPb = 0.8 (reasonable efficiency for packed column extractor)
• GLiPb limitation due to LiPb velocity (MHD pressure drops and corrosion)
• Module hydraulic section for LiPb : 0.33 m2
– for whole blanket VLiPb=1 mm/s GLiPb =0.085 m3 s-1 = 790 kg s-1
blanket
LiPb
13
KG
22
1
JJ
LiPb
LiPb
23 feb. 04Direction de l’Energie Nucléaire 13Wilfrid Farabolini
=0.08%
Working Point
• In existing He cooled fission reactor He leakage can be as high as 100% of the total inventory per year
– assumption: He inventory=400 m3 = 2250 kg LSG=1.63 Nm3/h • Tritium permeation through the SG is still to be evaluated.
– present assumption : KSG=0 (optimistic ? Maybe not so much if HTO)
MAX,5
1
SGSG
He
blanket
LiPb
J
J
LK
G1
K
G
2
21 He
LiPb
LiPb
4.3 Ci/kg
43 Ci/kg
23 feb. 04Direction de l’Energie Nucléaire 14Wilfrid Farabolini
Working point with He coolant contamination limit
• The acceptable limit for the He contamination is sometimes reported to be 1Ci/kg = 10-7 kg of T per kg of He.
23 feb. 04Direction de l’Energie Nucléaire 15Wilfrid Farabolini
Tritium extraction strategy
• Oxidize the T in HTO (H2O injection in He coolant, oxidation bed for purge gas)
• Extract tritiated water by zeolithe or cold trap• Advantages : develop natural oxide barriers both in blanket and in SG, much
less permeation for HTO than for T2
• Drawbacks : release limit for HTO is 10 times more stringent than for T2
WaterTrap
Chemical adjust
Heat exchanger
Water Trap
Chemical adjust
HCLL modulegas /
liquid column
= 0.08 %
H2O + HTOH2O + HTO
He coolantHe extraction LiPb
H2O 1000 ppmH2 100 ppmH2 0.1%
He + H2 + HTOxidation
bed
23 feb. 04Direction de l’Energie Nucléaire 16Wilfrid Farabolini
On going studies
• Refinement of the blanket permeation flow computation (J3)– Finite elements modelling (conduction and convection of heat
and of tritium concentration)
– Local temperature,
– LiPb flow (MHD, temperature convection, section variations, pressure drop),
– Soret effect (permeation driven by temperature gradient)
• Evaluate tritium permeation via the Steam Generator• Evaluate reasonable He leak rate for the whole coolant circuit• Evaluate the maximum He purification flow rate capability
– If 4 x 50000 Nm3/h no permeation barrier needed
• Ensure the feasibility of the tritium extraction strategy
Power Plant Conceptual Study (model AB)
23 feb. 04Direction de l’Energie Nucléaire 17Wilfrid Farabolini
Possible 2D modelling of the HCLL module
Tritium production rate (at / cm3.neutron)
0,0E+00
1,0E-03
2,0E-03
3,0E-03
4,0E-03
5,0E-03
6,0E-03
7,0E-03
0 100 200 300 400 500 600 700 800 900
module radial dimension (mm)
Neutron code (Tripoli)Thermal-mechanical code (cast3m)
LiPb flow and Tconvection viacast3m_fluid
T diffusion andpermeation via
cas3m_fluid(heat-like)
Cin
Cout
P