Experimental durability studies of electrolysis cell materials for water detritiation system

The radiation durability of the solid-polymer-electrolyte (SPE) water electrolyzer composed of the Water Detritiation System (WDS) was investigated. A series of gamma-ray and electron beam irradiation tests of Nafion N117 ion exchange membrane, a key polymer in a SPE electrolyzer, beyond ITER-WDS requirement (530 kGy) indicated Nafion N117 has enough radiation durability up to 1600 kGy from the view points of mechanical strength and ion exchange capacity. A gamma-ray irradiation test of the whole commercial SPE cell up to 530 kGy indicated entire loss of electrolysis function mainly because of the degradation of PTFE for insulator. To keep electrolysis function of a SPE cell up to 530 kGy, we suggest replacing PTFE with polyimide. A gamma-ray irradiation test of soaking Kapton polyimide observed no serious damage in strength up to 850 kGy. Concerning rubber material for Oring seal, we observed that soaking VITON rubber keeps the constant value of tensile strength up to 850 kGy. Moreover organic elution was not observed from a soak of VITON. From the viewpoint of stable strength and organic elution, VITON is a first candidate for rubber material. (orig.)