Recent activities on water detritiation technology in JAEA

原子力機構におけるトリチウム水処理システムに関する最近の研究活動

岩井 保則; 久保 仁志*; 大嶋 優輔*; 野口 宏史*; 谷内 淳一*

Iwai, Yasunori; Kubo, Hitoshi*; Oshima, Yusuke*; Noguchi, Hiroshi*; Taniuchi, Junichi*

原子力機構は核融合DEMO炉の実現に向けてCECEプロセスによるトリチウム水処理技術の高度化に取り組んできた。高度化に向けた研究として、(1)高濃度トリチウム水を電解処理する電解槽に使用するイオン電解質膜の耐久性評価とさらなる耐久性を付与させる電解質膜の改良研究、(2)高濃度トリチウム水に接液するゴムシールへのトリチウム水の収着挙動、(3)新たな製造法による疎水性触媒の創製と水蒸気-水素間水素同位体交換反応を促進の実証、に取り組んできた成果を報告する。電解質膜の3年もの長期にわたる1.4TBq/kgの高濃度トリチウム水への連続接液による機械的強度およびイオン交換容量の低下は同線量の電子線または線照射時の変化と同等であった。ゴムシールへのトリチウム水の収着量変化のついては、1500kGyまで電子線照射した試料を8年以上にわたり接液させた結果として放射線により構造損傷により収着量が照射線量の増加に伴い増加する傾向を見出した。原子力機構と田中貴金属工業が共同開発した新規製造法による疎水性触媒は耐熱性や耐放射線性に優れ、いままで最も性能が良かった高分子系疎水性触媒の1.3倍の効率を示すことを明らかとした。

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.