tritium permeation in hcll/dcll
DESCRIPTION
Tritium Permeation in HCLL/DCLL. Brad Merrill 1 , Phil Sharpe 1 , Dai-Kai Sze 2 1 INL Fusion Safety Program 2 UCSD. FNST Meeting UCLA, August 12 th -14 th , 2008. Presentation Overview. - PowerPoint PPT PresentationTRANSCRIPT
FNST Meeting UCLA, August 12th-14th, 2008
Brad Merrill1, Phil Sharpe1, Dai-Kai Sze2
1INL Fusion Safety Program2UCSD
Tritium Permeation in HCLL/DCLL
Presentation Overview
• This presentation examines Dual Cooled Lead Lithium (DCLL) and Helium Cooled Lead Lithium (HCLL) blanket tritium inventory and permeation rates as impacted by tritium:
Solubility in PbLi
First wall (FW) implantation
Reduced turbulent mass transport in PbLi
• The results are based on a TMAP model developed for the ARIES-CS DCLL design, with the model modified to give an intermediate helium cooling system to Rankine cycle in place of ARIES-CS Brayton cycle
• This TMAP model was also modified to simulate a HCLL blanket in ARIES-CS based on Melodie experimental results
• Conclude with a summary
ARIES-CS Design Parameters
Fusion Thermal Power in Blanket 2480 MW
Typical Module Dimensions ~4 m2 x 0.62 m
Tritium Breeding Rate ~400 g/d
PbLi Inlet/Outlet Temperatures 464/737°C
PbLi Inlet Pressure 1 MPa
Typical Inner Channel Dimensions 0.26 m x 0.24 m
Average PbLi Velocity in Inner Channel ~0.04 m/s
Fusion Thermal Power removed by PbLi 1323 MW
PbLi Total Mass Flow Rate 25,910 kg/s
Maximum PbLi/FS Temperature 472°C
He Inlet/Outlet Temperatures 385/460°C
He Inlet Pressure 10 MPa
Typical FW Channel Dimensions (poloidal x radial) 2 cm x 3 cm
He Velocity in First Wall Channel 46 m/s
He Inlet/Outlet Temperatures 385/460°C
Total Mass Flow Rate of Blanket He 3559 kg/s
Maximum Local ODS/RAFS Temperature at FW 654/550°C
Layout of ARIES-CS Power Core
ARIES-CS Power Parameters
ARIES-CS Tritium Extraction
• All PbLi component models (blanket gaps, pipes, permeator, and HTX) account for turbulent enhanced transport of tritium in the PbLi
• Correlationa proposed by Scott Willms used to model turbulent mass transport enhancement:
• Tritium solubility and diffusivity correlations developed by Reiterb and Teriac
Vacuum
QPb-17Li
CT,I
Niobium Membrane
T2
T2
Qvacuum
QPb-17Li
CT,O
Vacuum Permeator Concept
CT,Bulk
QPb-17Li
CT,S1
Or CT,S3 basedon molecularrecombination
CT,S2
Membrane diffusion
Pb-17Limass transport
( )S1T,BulkT,mT CC K −=Γ
x
CD- T
TT ∂∂
=Γ
2rT2 S3T,C α=Γ
0.3460.913
17LiPbT,
tubem ScRe 0.0096 D
DK=
−
17Li-PbS,
NbS,
S1T,
S2T,
K
K
C
C=
P KC sS3T,=
aHarriot and Hamilton, Chem Engr Sci, 20 (1965) 1073bReiter, FED 14 (1991) 207-211 cTeria, J. Nucl. Mater. 187 (1992) 247-253
s
m 27000/RT)exp(2.5x10D
Pam
T 1350/RT)exp(n2.32x10K
27
1/23PbLi8
s
−=
−−=
−
−
Schematic of ARIES-CS DCLL TMAP Model
Concentric pipesPbLi
Permeator
PbLi core
He/He FS HX
Non-Hartmann Gaps
Hartmann Gaps
First wall
Second wall
Rib walls
Back plate
Tritium cleanupsystem
Helium pipes
Shield Manifolds
IntermediateHelium Cycle
He/PbLi Nb HX
He/H2O Al HX
Tritium Inventory and Permeation Results For DCLL
• Based on TMAP results, increasing the solubility of tritium in PbLi by 100 increases the PbLi tritium inventory by ~12, but surprisingly reduces the reactor structural inventory and permeation rate
• This is due to the fact that the concentration jump at all PbLi/metal interfaces drops by 100 while the PbLi concentration increase of ~12 produces a balance between tritium production and extraction
• Tritium release is at or near allowable
Ks-Reiter 100 x Ks-Reiter FW Implantation
Km/5
Tritium source ~400 g/d ~400 g/d ~940 g/d ~400 g/d
Inventory
Structure1 335 g 86 g 2500 g 1850 g
PbLi 1.0 g 11.5 g 2.6 g 3.0 g
Release2 0.9 g/a 0.03 g/a 3.4 g/a3 3.0 g/a3
Permeator overall efficiency 70% 7.7% 73% 26.5%
Tritium pressure
PbLi 0.17 Pa 1.3x10-3 Pa 0.86 Pa 1.1 Pa
Helium 1.4x10-2 Pa 9.0x10-4 Pa 0.9 Pa 0.5 Pa
Tritium global balance
Permeator 99.8% 99.9% 98.2% 96.7%
Helium cleanup system 0.15% 2.0x10-2% 1.7% 2.4%
Leaked 1.0x10-2% 2.0x10-3% 0.1% 0.2%
Permeates to VV 4.0x102% 8.0x10-3% 0% 0.7%
Permeation into Rankine cycle
Intermediate helium cycle 360 Ci/a5 93 Ci/a 2160 Ci/a5 1690 Ci/a5
Direct (required reduction)4/5 47/4.7x103
0/2
1.7x103
/1.7x105
1.1x103
/1.1x105
198% of this inventory is in the Nb alloy HTX and because reactor has 6 sectors only 1/6th is at risk during most accident
299% ventilation flow cleanup is assumed3Limit is < 1 g/a4Based on CANDU water concentration of ~1
Ci/kg (34,000 Ci/a allowed into Rankine cycle)5Based on US PWR water concentration of ~ 1
mCi/kg (340 Ci/a allowed into Rankine cycle)
Melodie* Results used to Investigate Extraction Column Tritium Removal for an ARIES-CS HCLL Blanket
*N. Alpy, et al., FED, 49-50 (2000) 775-780.Sulzer Column
(not a 750 Y series)
20 cm
Structured packing
80 cm
• The extractor column used in Melodie experiments was a Sulzer Mellapak 750 Y series
• The extraction column was 60 mm in diameter, 800 mm in height, and had an area packing of 750 m2/m3
Schematic of ARIES-CS HCLL TMAP Model
PbLi Pipes
PackedColumns
PbLi core PbLi/He HXPoloidalGaps
Radial Gaps
First wall
Second wall
Rib walls
Back plate
Helium pipes
Shield Manifolds
823 K
673 K
He/He FS HX
Tritium cleanupsystem
IntermediateHelium Cycle
He/H2O Al HX
Purgegas
Melodie Experimental Loop Results for Sulzer Extraction Column and Application to ARIES-CS
• Melodie measured extractor efficiencies were ~25%
based on concentration, i.e. • For this TMAP model, the reactor PbLi processing flow
rate is assumed to be 300 kg/s, giving a change out rate
of eight times per day• All external volumes (PbLi - manifolds, pipes, HTX) were
scaled to the 300 kg/s (from the DCLL 26,000 kg/s) and all
turbulent mass transport terms set to diffusion only• Extractor PbLi flow rate per column was set at 50 l/h• ARIES-CS will require ~2430 parallel extractor column
paths, and at an efficiency of ~25% will also need five
stages per path (i.e., 12150 Melodie type extractors) – an
occupational radiation exposure problem based in DCLL
TBM analyses• The counter flow gas rate per column set at 100 Ncm3/min• A film thickness of 0.2 mm was used to give an efficiency
of ~25% per stage in this TMAP
PbLi flow
PackingPlate
Gas flow
CT2 = PT2/kT
CT = Ks (PT2)1/2
Melodie Results
Schematic of TMAP Extractor Model
€
∝ pH2
Tritium Inventory and Permeation Results For HCLL
195% in of this inventory is in austenitic steel of extraction columns, and because there are 12,150 columns very little tritium is at risk in most accidents
299% ventilation flow cleanup is assumed399% of this permeation is from extraction
columns4Limit is < 1 g/a5Based on CANDU water concentration of ~1
Ci/kg (34,000 Ci/a allowed into Rankine cycle)6Based on US PWR water concentration of ~ 1
mCi/kg (340 Ci/a allowed into Rankine cycle)
• An increase in solubility by 100 increases the PbLi inventory by ~16 and increases HTX permeation, with the helium cleanup system now removing a large fraction of the tritium
• A tritium inventory of 0.9 kg for high Ks case could represent a radioactive release hazard for ex-vessel PbLi spills
• Tritium airborne releases are above allowable
• When implantation is considered, most of the implanted tritium remains in the helium cycles
Ks-Reiter 100 x Ks-Reiter FW Implantation
Tritium source ~400 g/d ~400 g/d ~910 g/d1
Inventory
Structure1 295 g 274 g 455 g
PbLi 60 g 864 g 60 g
Release2 130 g/a3,4 95 g/a3,4 145 g/a3,4
Extractor overall efficiency 80% 3.6% 80%
Tritium pressure
PbLi 2900 Pa 60 Pa 2925 Pa
Helium 2 Pa 14 Pa 130 Pa
Tritium global balance
Extraction columns 81.5% 55.5% 33%
Helium cleanup system 7.3% 30.0% 60%
Leaked 9.2% 6.5% 7.0%
Permeates to VV 2.3% 8.0% 0%
Permeation into Rankine cycle
Intermediate helium cycle 2890 Ci/a6 5930 Ci/a6 12,060 Ci/a6
Direct (required reduction)5/6 3.1x103
/3.1x105
1.3x104
/1.3x106
5.3x104
/5.3x106
Summary
• Based on the present models, an increase in tritium solubility above that measured by Reiter would increase the tritium inventory in the PbLi, decrease extraction efficiencies, but could reduce the structural tritium inventory and permeation rates in DEMO reactors
• Most of the tritium in a DCLL concept will be in the PbLi/helium HTX tube walls, and because Nb is a getter accidents that result in HTX cooling will not release significant quantities of tritium
• For the HCLL concept, the majority of the tritium inventory and permeation is associated with the extractor columns, which could be reduced by a better design or selection of column materials. In addition, the HCLL has a much higher PbLi tritium inventory, making ex-vessel PbLi spills a tritium release concern
• Tritium permeation into a simulated Rankine power cycle was compared against equilibrium tritium concentrations in CANDU and US PWRs, it appears to be difficult to maintain an equilibrium concentration of 1 mCi/kg (PWR concentrations) by permeation barriers and/or material heat exchanger choice
• Regardless of the blanket concept employed, FW tritium implantation represents a significant problem for a Rankine cycle; a FW coating is need on the plasma side
• However, these result are based on the assumption that a sufficient understanding of tritium behavior in the PbLi, at PbLi/metal or PbLi/gaseous interfaces is presently known. Based on present experimental information this is clearly not the case
• What can be inferred from these results is that fusion reactors tritium inventories and permeation rates are highly dependent on this information, and thereby the ability to predict accidental and routine release of tritium from fusion reactors
Postscript On Melodie Results
• If the simple TMAP extractor model is correct, then data from Melodie can be used directly to determine if Reiter’s solubility coefficient is reasonable for Melodie conditions, at least based on simple conservation equations
PbLi flow
PackingPlate
Gas flow
CH2 = PH2/kT
CH = Ks (PH2)1/2
Schematic of TMAP Extractor Model• Conservation of mass between phases:
( )
2
2
11
2
Hgs
s
lHl
Hl
Hl
Hl
Hll
Hl
Hl
Hls
ois
s
ois
oi
kTCKDA
QCC
Cfor solving
CCQCCCDA
=⎥⎥⎦
⎤
⎢⎢⎣
⎡⎟⎟⎠
⎞⎜⎜⎝
⎛ δ+η−=
−=⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−
+
δ
• Conservation of mass in liquid and diffusion:
2
2
121
1
Hsats
Hl
gHl
ls
l
s
pKC where
QC
kTQK
Q
DA
i
i
=
⎥⎥
⎦
⎤
⎢⎢
⎣
⎡−
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛ η−
η=δ
• Substituting the above and solving for film thickness:
Postscript On Melodie Results (cont.)
• Given the volume of the Melodie column (V=2.26x10-3 m3), a packing fraction of 80%, and a packing area density of 750 m2/m3, the packing (film) surface area is ~ 1.4 m2
PbLi flow
PackingPlate
Gas flow
CH2 = PH2/kT
CH = Ks (PH2)1/2
Schematic of TMAP Extractor Model
K 673T @ s
m3.76x10
min
Ncm 100Q
s
m1.39x10
hr
l50Q
s
m 2.0x10 D
K 673T
36
3
g
35
l
29-
===
==
=
=
−
−
• Given the other parameters of
where, Ks-max is the largest solubility that still results in
a film for the TMAP extractor model, which is found by setting the term in brackets in the film thickness equation to zero => Reiter Ks fits Melodie results
and using Melodie saturation pressures and efficiencies gives:
PH2sat
(Pa) η δ (mm)
Ks-max
/Ks-Reiter
Ks-δ=0.15 mm
/Ks-Reiter
1100 0.31 0.149 1.37 0.998
475 0.25 0.156 1.28 1.010
230 0.25 0.046 1.07 0.843
Schematic of ARIES-CS HCLL TMAP Model
PbLi Pipes
PackedColumns
PbLi corePbLi/He HX
PoloidalGaps
Radial Gaps
First wall
Second wall
Rib walls
Back plate
Tritium cleanupsystem
Helium pipes
Shield
Inter-cooler
Pressure boundary
Manifolds
BraytonCycle
823 K
673 K
Purgegas
Concentric pipesPbLi
Permeator
PbLi core
PbLi/He Nb HX
Non-Hartmann Gaps
Hartmann Gaps
First wall
Second wall
Rib walls
Back plate
Tritium cleanupsystem
Helium pipes
Shield
Inter-cooler
Pressure boundary
Manifolds
BraytonCycle
Schematic of ARIES-CS DCLL TMAP Model