A NEW PRESSURE SWING ADSORPTION (PSA) PROCESS FOR RECOVERY OF TRITIUM FROM THE ITER SOLID CERAMIC BREEDER HELIUM PURGE GAS

Pressure Swing Adsorption (PSA), which is a well established industrial process for separating and purifying industrial gases, is proposed for recovery of hydrogen isotopes from the ITER (International Thermonuclear Experimental Reactor) solid breeder He purge stream. The PSA process has an inherent advantage over a recently proposed Temperature Swing Adsorption (TSA) design because it allows much faster cycling (10 vs. 480 min.) and therefore has significantly (48 times) lower tritium inventory. The maximum tritium inventory for a 10 minute PSA cycle is less than 0.5 g of tritium, thus meeting an important safety goal of ITER. The PSA process is based on using molecular sieve 5A at 77 K, with pressure cycling from 1 - 2 MPa during the adsorption cycle, to a rough vacuum during regeneration. Experiments have been carried out to confirm the H-2/He adsorption isotherms on molecular sieve 5A, and to develop new data points at low H-2 partial pressures and a temperature of 77 K. A dynamic simulation model has been developed to facilitate system design and optimization. Simulation results indicate that a single-pass hydrogen isotope recovery of 50-80% is achievable, and that hydrogen purity of more than 99% is possible to obtain from the blanket purge stream containing only 0.1% total hydrogen in helium. Further experiments are underway to verify the dynamic simulation results and to investigate alternative adsorbent materials.