Clean-up Capability of an Emergency Detritiation System (II)

An emergency tritium removing system, using a precious metal/alumina catalyst, was designed and constructed in order to decontaminate tritium leaked accidentally into laboratory rooms. The performance of thee system was examined using a balloon for helium recovery or an aluminum vessel as a substitute of a laboratory room. Tritium gas containing about 10% tritiated methane (CH3T) as an impurity was introduced into the experimental room and then removed with an air flow rate of 72 m3/h. Tritium gas (T2) was removed satisfactorily, i.e. the reaction probability was unity, due to a Pd/Al2O3 catalyst (Nippon Jun Suiso Co. Ltd) at 200℃, while the tritiated methane could not be removed with a sufficient amount of efficiency: its reaction probability was below unity. It was found that the reaction probability of the tritiated methane became unity above 300℃ for this catalyst. On the basis of these results, it is estimated that the accidental leakage of tritium of 5Ci (which is the maximum permissible amount used in a day in this laboratory) into a laboratory room can be removed within an 18h period