Potential Tritium Processing/Control Needs for US ITER TBM

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Potential Tritium Processing/Control Needs for
US ITER TBM
Scott Willms Los Alamos National
Laboratory Presented at INL August 11, 2005
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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
• Non-ITER, non-tritium testing
• ITER year 1-10 tests
• ITER year 11-20 tests
• DEMO

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Tritium process overview
Recover tritium from He
Tritium control important throughout
Also use as test station
Use He to strip T from PbLi
PbLi loop
He loop
T permeation thru HX tubes
Recover tritium from He
Avg. T2 breeding rate 0.024 sccm
He loop
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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
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Summary of tritium processing concepts for
DCLL-Extraction of tritium from PbLi

• 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.

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Summary of tritium processing concepts for
DCLL-Extraction 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

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Issues associated with tritium extraction from
PbLi (DCLL)
Concept Issues
Vacuum permeator with Ta or Nb membrane (coated or uncoated) 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 Model ideal performance Compare to French data Consider alternate configurations Mass transfer coefficients Can this concept achieve needed low concentrations?
Vacuum disengager Can a falling PbLi drops be practically produced? Can counter-current system be practically produced? Can low concentrations be achieved? Mass transfer coefficients
Getter 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
Use heat exchanger to transfer tritium to He and subsequently separate T from He Can the HX be designed to remove heat and sufficient tritium? Requires effective He/T separation
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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 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
Cryogenic molecular sieve Is it practical to cycle gas between low and high temperatures?
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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 Dont 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
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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/adsorption of tritium in He at elevated temperatures Concept reliable Simple operation Need high temperature adsorbent Cyclic operation Tritium converted to waterneeds subsequent processing
Cryogenic molecular sieve Most tested option for tritium/He Effective Reliable Requires cooling stream to LN2 termperature Practical for DEMO?
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T, O, PbLi, wall system

• Tritium from PbLi to wall
• Dont know
• PbLi T(l) lt-gt Wall T(s)
• So currently work around with
• PbLi T(l) lt-gt T2(g)
• T2(g) lt-gt 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
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Highest priority topics

• Further systems modeling needed
• Tritium processing
• Tritium migration
• Extraction from PbLi
• 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

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Next steps

• Establish a baseline set of RD
• Prepare project information for RD
  (scope/schedule/budget)