Chemical state of tritium in Sr-Ce oxide ceramics and its removal characteristics (Cooperative research)

Nakamura, Hirofumi; Nishi, Masataka; Morita, Kenji*

As a part of the detritiation study from the fusion reactor materials, chemical state of tritium injected into Sr-Ce base oxide ceramic proton conductor, which is a candidate for a tritium recovery system, was investigated with thermal desorption method. The results indicated that the oxide has to be heated up over 1300K to remove tritium due to the OT bond formation in the oxide. On the other hand, tritium removal behavior from the oxide were also investigated by exposing to humid air, and the mechanism of tritium removal from the oxide was identified by the dependency of tritium removal amount and chemical state on the humidity. The results revealed that tritium removal rate by the air exposure was low, and that almost tritium was removed as the vapor form, which was attributed to the isotope exchange reaction between the OT bond on the surface and the protium in vapor. It was also found that small amount of tritium was removed as elemental form under the humid air exposure, which could be attributed to the solute tritium in the oxide and oxygen absorption to the oxygen deficit in the oxide. As a result, the difference of the detritiation mechanism exposed to the humid air on the chemical state of tritium in the oxide was clarified, and it could be a useful basic data for the optimization of detritiation method.