Long-Term Performance of Atmospheric-Detritiation Dryers

Abstract

ABSTRACTTritiated heavy water (DTO) accumulates in the process systems of a CANDU®a reactor due to neutron capture by the heavy-water moderator and coolant. After twelve years of service, the moderator in the Point Lepreau Generating Station has reached approximately 1.6 TBq/kg, and the total inventory exceeds 300 PBq. Point Lepreau uses nine desiccant dryers to control airborne heavy water and tritium. Ranging in size from 1 000 m3/h to 6 800 m3/h, the majority are single-bed, cocurrent-regenerated units filled with 13X or 4A molecular sieve. These dryers have operated almost continuously for twelve years without a significant breakdown. During the last thirteen years, their availability has exceeded 99% and they have routinely dried air to a dew-point temperature of −60°C or below. Tritium emissions from the dried areas in the reactor building remain a small fraction of the tritium released into the reactor building. The keys to the success of this detritiation system are the mechanical simplicity of th...