Isotopic Exchange in Air Detritiation Dryers

Air detritiation dryers at fusion facilities require high detritiation factors to minimize environmental releases. To increase the detritiation factor in air dryers, we have investigated a technique of eluting the residual adsorbed tritiated water on a molecular sieve bed that uses H₂O steam washing during regeneration. The method relies on additional detritiation of the air stream occurring through isotopic exchange between the tritiated water vapor passing through a dryer bed with previously adsorbed non-tritiated water. Isotopic exchange is studied in both an operating industrial-scale air dryer, where the bed has been pretreated to remove tritium, and in a small laboratory bed. A mathematical model is presented to quantify the isotopic exchange process.