Download Tritium Release Experiments - UCLA

Potential Tritium Processing/Control Needs for US ITER
TBM
Scott Willms
Los Alamos National Laboratory
Presented at
INL
August 11, 2005
Overarching drivers
• Must handle tritium in TBM properly
– For safety concerns
– To accurately characterize TBM performance
• In addition TBM will be a unique opportunity
– To develop and demonstrate tritium extraction concepts
– To characterize tritium migration
– To test tritium containment technologies
• Time phasing
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–
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Non-ITER, non-tritium testing
ITER year 1-10 tests
ITER year 11-20 tests
DEMO
Tritium process overview
Recover tritium
from He
He
Tritium control important throughout
T2
Permeator
Also use as
test station
He, T2
Breeder, T2, He
Use He to
strip T from
PbLi
T2
Breeding
Dual Coolant
Blanket
PbLi loop
He
To Tritium
Plant
Breeder, T2
Breeder
He, T2
He loop
T permeation
thru HX tubes
T2
Heat
Exchanger
Permeator
Avg. T2 breeding
rate: 0.024 sccm
To Tritium
Plant
T2/Breeder
Separator
He
Heat
Exchanger
T2, He
He
Recover tritium
from He
He loop
Comparison of ITER TBM and DEMO
Tritium
Control/Exraction
Consideration
ITER TBM
DEMO
Amount of tritium
Grams
Kilograms
Tritium control (prevent
leaks to unwanted
locations)
Priority
Priority
Data for breeder
performance
Priority (emphasis on
fundamental data)
Priority (emphasis on
practical operation)
Scalability of concept
Secondary
Priority
Usefulness of tritium
bred
Inconsequential
Priority
Summary of tritium processing concepts for DCLLExtraction of tritium from PbLi
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•
•
•
•
•
•
Vacuum permeator with Ta or Nb membrane (bare or coated)
Vacuum permeator with Pd or Pd alloy membrane
Vacuum permeator with ferritic steel membrane
Bubble column
Vacuum disengager
Getter
Use heat exchanger to transfer tritium to He and subsequently
separate T from He.
Summary of tritium processing concepts for DCLLExtraction of tritium from He
•
•
•
•
Vacuum permeator with Pd alloy membrane
Vacuum permeator with Ta or Nb membrane (bare or coated)
Oxidation/adsorption of tritium in He at elevated temperatures
Cryogenic molecular sieve
Issues associated with tritium extraction from PbLi (DCLL)
Concept
Issues
Vacuum permeator with Ta or Nb membrane (coated or
uncoated)
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Mass transfer coefficients
PbLi compatibility with membrane on retentate side
Stability of membrane on vacuum side given potential attack of
O, N and C
Liquid-solid equilibrium of T/PbLi with membrane
Can vacuum side be sufficiently controlled?
What happens in credible off-normal conditions?
Long-term “permeability” of membrane in this environment
Stability/effectiveness of coatings
Vacuum permeator with Pd or Pd alloy membrane (coated
or uncoated), FS

Issues similar to above, but stability of membrane expected to be
very different since it should not oxidize
Bubble column
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Model ideal performance
Compare to French data
Consider alternate configurations
Mass transfer coefficients
Can this concept achieve needed low concentrations?
Vacuum disengager
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Can a falling PbLi drops be practically produced?
Can counter-current system be practically produced?
Can low concentrations be achieved?
Mass transfer coefficients
Getter
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Can a high temperature tritium getter be placed in the PbLi stream
to achieve low tritium concentrations over practical times?
How will getter be dispositioned after use?
Mass transfer coefficients


Can the HX be designed to remove heat and sufficient tritium?
Requires effective He/T separation
Use heat exchanger to transfer tritium to He and
subsequently separate T from He
Issues associated with tritium extraction from He (DCLL
and Ceramic Blanket)
Concept
Issues
Vacuum permeator with Pd alloy membrane

Will this concept work at blanket conditions, reducing the
tritium concentration so that downstream systems will not be
adversely impacted?
Vacuum permeator with Ta or Nb membrane (bare or
coated)

Higher permeability materials may extend the Pd alloy
permeator performance to an acceptable level
Stability of membrane
Oxidation/adsorption of tritium in He at elevated
temperatures

Cryogenic molecular sieve
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Conversion of all tritium to water will prevent tritium
permeation outside of system
Need high temperature water collection system
Need regeneration scheme
Need to recover tritium from water
Is it practical to cycle gas between low and high
temperatures?
Comparison of PbLi systems
Concept
Advantage
Disadvantages
Vacuum permeator
with Ta or Nb
membrane (coated
or uncoated)
Good single-stage performance
Easy to operate
More complicated to construct
Fragile
Vacuum permeator
with Pd or Pd alloy
membrane (coated
or uncoated)
Good single-stage performance
Easy to operate
More complicated to construct
Somewhat fragile
Expensive
Bubble column
Easy and inexpensive to construct
Reliable
Flexible operating possibilities
Single-stage performance likely insufficient
Multi-stage operation bulky and
complicated
Vacuum disengager
Somewhat simple/inexpensive
device
Able to make mass transfer
distances short
Spray fouling
Don’t know if performance would be
sufficient
Getter
Simple
Low concentration feed leads to short time
to regen
Performance after regen may not be good
Material not identified
Cyclic operation
Use heat exchanger
to transfer tritium to
He and subsequently
separate T from He
Simple
Lots of tritium may travel this path
anyway, so it is a waste of effort to
extract tritium up-stream
Tritium migration concerns
Comparison of He systems
Concept
Advantage
Disadvantage
Vacuum
permeator
with Pd alloy
membrane
Single-stage, continuous operation
Relatively simple
Performance attractive, but not tested in
blanket concept
Vacuum
permeator
with Ta or Nb
membrane
(bare or
coated)
Single-stage, continuous operation
Relatively simple
Less expensive
Higher performance
Reliability
Oxidation/ads
orption of
tritium in He
at elevated
temperatures
Concept reliable
Simple operation
Need high temperature adsorbent
Cyclic operation
Tritium converted to water…needs
subsequent processing
Cryogenic
molecular
sieve
Most tested option for tritium/He
Effective
Reliable
Requires cooling stream to LN2 termperature
Practical for DEMO?
T, O, PbLi, wall system
• Tritium from PbLi to wall
– Don’t know
• PbLi + T(l) <-> Wall + T(s)
– So currently work around with
• PbLi + T(l) <-> T2(g)
• T2(g) <-> Wall + T(s)
• Gives answer, but there is no T2(g)
– Need real experiment
• Also, what is the fate of T and O in
PbLi?
– If T turns into water, permeation will
be very different
– Does not appear water will form, but
an experiment is needed
Species
Moles
Li
17
Pb
1
Li2O
0.002
LiT
0.002
Highest priority topics
• Further systems modeling needed
– Tritium processing
– Tritium migration
• Extraction from PbLi
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–
–
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Tritium mass transfer coefficients in PbLi
Bubbler design evaluation
Bubbler data
Vacuum permeator
• Extraction from He
– Vacuum permeator
• Fate of tritium in PbLi
– LiH, Li with H2 in solution, Li with H+?
– Mechanism/rate of H transport into wall
• Tritium migration
– Permeation barrier modeling and experiments
Next steps
• Establish a baseline set of R&D
• Prepare project information for R&D (scope/schedule/budget)