Practical-scale tests of cryogenic molecular sieve for separating low-concentration hydrogen isotopes from helium

There are a number of cases in fusion fuel processing where low-concentration hydrogen isotopes need to be separated from helium. Usually the helium is a purge gas used to move hydrogen isotopes from one location to another. One of the most notable applications is associated with removing tritium from a solid ceramic breeder. For some designs which have been considered, helium with about 1 % protium is purged through the ceramic. The protium exchanges with tritium which has been bred in the solid. The resulting gas composed of helium (∼99%), protium (∼1%) and tritium (∼0.01%) flows out of the blanket and, for further processing, requires separation of the hydrogen isotopes and the helium. Earlier bench-scale (about 50 cc of sieve) work at the Tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory examined a number of adsorbents for their suitability for separating low-concentration hydrogen (no tritium) from helium. One of the effective adsorbents was Linde 5A molecular sieve. The purpose of this paper is to report practical-scale experiments including tritium. These tests used existing cryogenic molecular sieve beds (MSB'S) which each contain about 1.6 kg of Linde 5A molecular sieve