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Tritium Permeation Issue, Plan and Progress

Tritium Permeation Issue, Plan and Progress. ITER. Dai-Kai Sze. University of California, San Diego Presented at the ITER TBM Project Meeting UCLA, Feb. 23-25, 2004. Statement of Problem. ITER. Fusion blankets have high tritium partial pressure.

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Tritium Permeation Issue, Plan and Progress

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  1. Tritium Permeation Issue, Plan and Progress ITER Dai-Kai Sze University of California, San Diego Presented at the ITER TBM Project Meeting UCLA, Feb. 23-25, 2004

  2. Statement of Problem ITER • Fusion blankets have high tritium partial pressure. • The temperature of the blanket is high. • The surface area of the heat exchanger is large, with thin wall. • Those are the perfect conditions for tritium permeation. • The allowable tritium loss rate is very low.

  3. Typical tritium partial pressure ITER For LiPb 0.014 Paa For flibe 380 Paa For Li 2.6X10-8 Pab For solid breeder 0.6 Pac • The tritium partial pressure increase per coolant path. • Assuming tritium concentration of 1 ppm . • With a purge gas flow rate of 104 liter/s.

  4. Tritium Permeation ITER Typical parameters of heat exchangers are: Temperature 500C Surface area 2.5X104 m2 Wall thickness 1 mm Tritium permeability in FS = 0.46 mol T2-mm/d-m2-atm0.5 If the tritium partial pressure is 1 Pa, the tritium permeation rate will be 218 g

  5. ITER Methods to reduce Tritium Permeation • Develop efficient tritium recovery system from the breeding material. • Develop high performance tritium diffusion barrier. • Convert tritium from elementary form to oxide form. • Secondary tritium clean up from the intermediate coolant. • Tritium clean up from the power conversion medium.

  6. Canada Experience ITER • CANDU loss about 10 Kg/hr coolant water, and 2-5 Kg/hr of moderator water • About 95% of the water is recovered. • About 50% of the tritium emission is from the water loss. • Only about 5-10% of the emission is caused by tritium permeation.

  7. Tritium loss from fusion ITER • Permeation is a much important path for tritium loss for fusion than for CANDU, because tritium is in elementary form. • Tritium loss caused by coolant loss, either water or He, has to be included. • CANDU losses about 200 Ci/d, and it has a much smaller tritium throughput than fusion. • Is it reasonable to expect fusion can achieve a loss rate close to 1 Ci/D?

  8. Where are we? ITER • Tritium recovery processes from breeder materials are in good shape. • Tritium diffusion barrier development did not obtain the required performance. • Tritium oxidation kinetics has been studied, but results vary. • Some efforts, mainly for safety concerns, have been spent to develop an intermediate heat exchanger.

  9. Where are we? (Cont.) ITER • The leakage of the coolant, especially water and He, needs to be carefully assessed. • The economy of the tritium clean up system depends strongly on the coolant leakage rate. • Loss coolant recovery rate, was 95% of the CANDU system, will have major impact on the tritium loss rate. • SR tritium loss rate is about 4 g/y (100Ci/d), while the CANDU reactor loss about 200 Ci/d, is it reasonable to limit the tritium loss rate to a fusion power plant to between 1 to 30 Ci/D? • It will be useful for us to get back the last VG for further discussion.

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