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Tritium Extraction from a DCLL Blanket

Tritium Extraction from a DCLL Blanket. Prepared by: Scott Willms (LANL) Collaborators: Brad Merrill (INL), Siegfried Malang (Consultant), Clement Wong (GA), Dai-Kai Sze (UCSD) Presented by: Jim Coons (LANL) Coordinating Meeting on R&D for Tritium and Safety Issues in Lead-Lithium Breeders

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Tritium Extraction from a DCLL Blanket

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  1. Tritium Extraction from a DCLL Blanket Prepared by: Scott Willms (LANL) Collaborators: Brad Merrill (INL), Siegfried Malang (Consultant), Clement Wong (GA), Dai-Kai Sze (UCSD) Presented by: Jim Coons (LANL) Coordinating Meeting on R&D for Tritium and Safety Issues in Lead-Lithium Breeders 11 June 2007 Idaho Falls, ID LA-UR-05-1711

  2. Outline DCLL process overview Conventional separator T removal via vacuum permeator Model Mass transfer coefficient Parametric study DEMO design Issues Conclusions

  3. DCLL process overview Recover tritium from He 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

  4. Pressure in T2 separator tank if all tritium is contained (no permeation, no stripping, etc.)

  5. Rough estimate for tritium removal pathways from PbLi with both tank pump off and HX permeation

  6. Evaluating the possibility of using a vacuum permeator for tritium separation from Pb-Li Recover tritium from He Use Permeator to recover 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

  7. Low Pressure Permeator Experimental Apparatus

  8. Experimental Setup

  9. With 25 sccm H2, the retentate and permeate are initially in agreement and ultimately breakthrough is observed at about 375 sccm. Constant 25 sccm H2 Increasing N2 450 C

  10. Mathematical model for PbLi/T permeator • A component balance describes the tritium mass fraction along the membrane length • Tritium transport to the membrane surface is described by a mass transfer coefficient • The effective tritium partial pressure at the membrane surface is given by the solubility • Permeation depends on the permeability

  11. Comparison of mass transfer coefficient results

  12. xi x0 liq to solid xfer liq bulk-to-surface mass xfer pr pp permeation through membrane solid to gas xfer The mass transfer coefficient for this system was estimated from general correlations • 10 general correlations were considered • The following correlation appeared to be the most appropriate: --Harriott and Hamilton, Chem Engr Sci, 20, 1073, 1965 • However, this correlation was developed with benzoic acid and glycerin-water mixtures at room temperature—considerably different from 700 C PbLi and tritium

  13. Values used to solve the model

  14. Using these base conditions the tritium concentration down the length of the permeator was determined

  15. Performance depends strongly on the mass transfer coefficient

  16. Wall thickness

  17. Surface Concentration

  18. Permeability

  19. PbLi Flowrate

  20. Feed concentration

  21. Tube diameter does significantly affect performance Tube Diameter

  22. Permeate pressure

  23. Considerations for a practical PbLi permeator • PbLi flowrate for Demo: 26270 kg/s • With 1 cm dia. tubes and 5 m/s flow velocity: 7592 tubes • Total Nb required for 5 m tubes: 2.6 tons • Total cost for Nb: ~$0.5M (?) • Diameter of vessel to contain tube cross sections + twice that area for space between tubes: 1.7 m This permeator is a substantial vessel, but one that can practically be constructed

  24. While this initial analysis indicates that a PbLi permeator may be feasible, there are many issues that must be resolved • Measured mass transfer coefficients for the PbLi-T system • Compatibility of PbLi with Nb at 700 C • Additional resistances to tritium permeation such as surface resistance? • At the PbLi-membrane interface, is the effective partial pressure exerted by tritium indeed given by the solubility equation? (this may be a very different mechanism with a very different rate) • What pressure can be practically maintained on the permeate side of the membranes? • Will Nb tubes degrade due to reactions such as oxidation? Will a surface treatment be needed?

  25. Conclusions • Tritium permeation through the heat exchanger materials will be substantial and cannot be neglected • Tritium can be recovered from helium streams with gas permeators and other technologies • A reasonable plan for ITER TBM ancillary equipment is to include a helium bubbler on the PbLi loop and permeators on both He loops • A potentially attractive option is a PbLi permeator to directly remove tritium from PbLi. Based on present information such a device might be practical. • Whether or not it is actually practical would require considerable R&D

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