Summary of Tritium Issues

1. Summary of Tritium Issues Dai-Kai Sze, UCSD Phil Sharpe, INL FNST Meeting UCLA, August 12-14, 2008

2. Tritium issues for solid breeder blanket • Using He purge for tritium recovery from solid breeders with additional H has been demonstrated. • There has been no design of the He purge system, including manifold and purge distribution and pressure drop. • It has been assumed that a permeation barrier can be developed to limit tritium permeation to the coolant. • If permeation barrier can not be developed, large fraction of the bred tritium will be permeated into the primary coolant.

3. Tritium issues for solid breeder blanket(continue) • If the primary coolant goes directly to a steam generator, a very efficient recovery system from the He coolant needs to be developed. • If the primary coolant goes to a recuperator HX (for a He cycle), the tritium permeation problem is not near as severe. • He leakage is another concern for tritium control. • Tritium production, removal and inventory in the Be multiplier is another conern.

4. Tritium leakage for PbLi based blanket • The basic data between tritium and PbLi are not available. • There is large discrepancy of the experimental results on the tritium solubility (tritium partial pressure and tritium concentration in PbLi) in PbLi. • Permeation barrier development has not been successful. • Radiation will eliminate the diffusion barrier effect on the tested barrier. • Proposed tritium recovery process has only ~ 30% efficiency. • Proposed tritium recovery process based on permeation barrier needs to be tested.

5. Temperature, ˚C 727 560 440 350 282 225 Absorption techniques Fukada Aiello Desorption techniques No consensus on data range, nor even behavior at low partial pressure… Tritium Transport Data Variations, cont. Sievert’s Constant Variations: courtesy I. Ricapito, ENEA CR Brasimone

6. Key Limit for Tritium Issues The tritium system need to be designed based on the following limits: • Tritium inventory needs to be < 100g. • The tritium loss rate needs to be < 10 Ci/d. • The cost of the tritium processing system needs to be < 100 M$. Those are order of magnitude numbers, and can change by a factor of 2, but not by a factor of 10.

7. Case for solid breeder Tritium production rate 500g/d Purge gas flow rate 10(4) l/s Tritium partial pressure in purge 0.6 Pa Coolant flow rate 10(5) l/s Tritium carried away by purge 45 g/d Tritium permeated into coolant 455 g/d Tritium partial pressure in coolant 0.056 Pa Allowable tritium partial pressure over SG 2X10(-7) pa * Required tritium clean up efficiency 99.999% • Allowable tritium partial pressure over recuperator HX can be much higher • Assumed a permeation coating has a reduction factor of 100

8. Case for PbLi blanket For PbLi based blanket, the tritium partial pressure is 0.014 Pa. This partial pressure is highly uncertain, because of the different results of the tritium solubility. The PbLi will be fed to a steam generator, with an allowable tritium partial pressure of 2X10(-7) pa.* The required tritium clean up efficiency needs to be 99.6%. The demonstrated tritium recovery process has an efficiency of on 30%. For the tested tritium recovery system, it is not clear which step is the rate limiting step for tritium recovery. There is no sufficient data, or established tritium recovery system, for the tritium recovery system of a PbLi based blanket. * Assuming a permeation barrier can be developed with a barrier factor of 100.

9. R/D required for solid breeder blankets • Develop effective, and radiation resistant permeation barrier (X100 to 1000). • Develop cost effective and efficient tritium recovery system from the He coolant. • Develop highly effective, and reliable permeation barrier (X1000 to 10,000). • Design an IHX to provide additional tritium diffusion barrier. • Design the system with a close cycle gas system. • Investigate tritium recovery process from Be.

10. R/D required for PbLi based blankets • Establish fundamental data between T/PbLi interaction. • Develop effective tritium recovery process from PbLi. • Develop highly effective, and reliable permeation barrier (X1000 to 10,000). • Design an IHX to provide additional tritium diffusion barrier. • Design the system with close cycle gas system.

11. Summary • The data base available today is not sufficient to design a tritium recovery and control system, for either solid breeder, or PbLi based blankets. • There is great deal of certainty that the tritium can be recovered at the production rate, with tritium inventory below the deign limit of 100g. • There is a great del of uncertainties that the tritium loss rate can be less than 10 Ci/d for solid breeder based blanket. • There is not sufficient data base for tritium/PbLi interaction to design a tritium system for the PbLi based blanket.