Research and development on radiation durability of core components of water detritiation system for fusion reactors

Iwai, Yasunori; Kubo, Hitoshi*; Oshima, Yusuke*

Water detritiation technology for the Combined Electrolysis Catalytic Exchange (CECE) process has been developed over the years in Japan Atomic Energy Agency (JAEA) for the Japanese DEMO fusion reactor. The research interest is in (1) durability of a commercial polymeric ion exchange membrane for tritiated water electrolyzer and improvement of a membrane for the enhance in durability, in (2) sorption behavior of tritiated water in elastomers for promising seal materials of the electrolyzer, and in (3) development of hydrophobic catalyst for the reaction of hydrogen isotope exchange between hydrogen and water vapor in the Liquid Phase Chemical Exchange (LPCE) column. For the durability of ion exchange membrane, durability of Nafion ion exchange membrane immersed into 1.3810 TBq/kg of highly concentrated tritiated water has been demonstrated at room temperature for up to 3 years as a Broader Approach activity. The changes in mechanical strength and ion exchange capacity after immersing in tritiated water are well consistent with those irradiated to an equivalent dose with rays or electron beams. As for the sorption behavior of tritiated water in elastomers, change in sorption behavior of water in elastomers irradiated up to 1500 kGy has been evaluated for more than 8 years. For the hydrophobic catalyst, the Japan Atomic Energy Agency and Tanaka Kikinzoku Kogyo K.K developed a new method of manufacturing catalysts involving hydrophobic processing with an inorganic substance base. The catalyst created with this method has achieved the highest exchange efficiency, equivalent to 1.3 times the previously most powerful efficiency.