Tritium recovery from tritiated water with a two-stage palladium membrane reactor

Abstract

A process to recover tritium from tritiated water has been successfully demonstrated at the Tritium Systems Test Assembly. A 2-stage palladium membrane reactor (PMR) is capable of recovering tritium from water without generating additional waste. A substantial amount of tritiated water will be generated in the International Thermonuclear Experimental Reactor both from torus exhaust and auxiliary operations. In addition, this process can be used to recover tritium from tritiated waste water being prepared for disposal in radioactive waste repositories. A large quantity of tritiated waste water exists world wide because the predominant method of cleaning up tritiated streams is to oxidize tritium to tritiated water. A series of cold (non-tritium) water processing experiments were run in preparation for the tritiated water processing tests. Optimum operating conditions were determined with these experiments. Tritium was recovered from a container of molecular sieve loaded with 2050 g (2550 std. l) of water and 4.5 g of tritium. The maximum water processing rate for the PMR system used was determined to be 0.5 slpm. A control method was developed to automatically liberate steam from the molecular sieve and add the desired amount of CO before injection into the PMR system. The maximum decontamination factor achieved in the 1st stage ranged from 100 to 260, depending on the inlet flow rate. Performance of the 2nd stage could not be measured because the outlet tritium concentration was below the background of the ion chamber used for analysis. Although the DF could not be measured, it is known that the DF was high because no tritium was detected, except during start-up, in the tritium waste treatment system that was downstream from the PMR system.