A Small Closed-Cycle Combined Electrolysis and Catalytic Exchange Test System for Water Detritiation

AECL has been actively involved in exploring advanced electrolysis technologies for its Combined Electrolysis and Catalytic Exchange (CECE) technology for water detritiation. A small-scale CECE system (mini-CECE) has been built and operated at AECL to explore its operation as a closed-cycle system with a proton-exchange membrane (PEM) type electrolysis cell. A similar mini-CECE system suitable for service with tritium concentrations up to 1000 Ci/kg(water) has been assembled, in collaboration with Tyne Engineering, for installation in a glovebox in AECL's Tritium Facility. These systems were developed as test-beds for membranes that had been selected for their expected tritium resistance. The systems allowed the measurement of membrane performance over long periods at very high tritium concentrations, as well as the ability to monitor any effects of membrane degradation products on the performance of exchange and recombiner catalysts.

Preliminary work has been done with Nafion-112 membrane samples by exposing them to gamma and beta radiation to determine their suitability for use in tritiated CECE system. Doses of up to 1250 kGy of gamma or 200 kGy of beta were applied. Visual observations showed that gamma irradiation at doses below 400 kGy produced severe damage to the membrane. No significant physical damage was observed for samples exposed to 200 kGy from tritiated water. However this level of exposure to either gamma or beta radiation was sufficient to significantly decrease membrane performance in fuel cell tests.