Development of ceramic electrolysis method for processing high-level tritiated water

高濃度トリチウム水処理のためのセラミック固体電解質法の開発

磯部 兼嗣; 鵜澤 将行*; 山西 敏彦; 栗田 晃一*

Isobe, Kanetsugu; Uzawa, Masayuki*; Yamanishi, Toshihiko; Kurita, Koichi*

核融合炉で発生する高濃度トリチウム水からのトリチウムの回収は、インベントリー管理や燃料循環の観点から重要な課題である。ITERでは高分子電解膜を用いた水処理法が採用されるものの、この処理法では放射線劣化のため高濃度トリチウム水の処理には対応できない。このような高濃度トリチウム水処理に適用可能な方法として、放射線劣化のないセラミック固体電解質を用いた水処理法がある。そこで、セラミック固体電解質を用いた水処理法に必要とされる水分解効率の高い電極の開発を行っている。今回、新たには酸化セリウム(セリア)を用いた2種類の電極を作製し、その水分解効率を評価したところ、最大で従来電極の3倍の効率を達成した。

The high-level tritium water is expected to be produced in the vacuum chamber and in a breeding blanket system. It is one of the key issues to recover tritium from the high-level tritium water from the viewpoint of tritium inventory control in the vacuum vessel as well as tritium recover as a fuel. A solid polymer electrolysis used in WDS (Water Detiritiation System) of ITER can not be applied for the high-level tritium water to avoid the radiation damage. A ceramic electrolysis would be only a method to recover tritium from the high-level tritium water. The water is decomposed by the reduction on the electrode in the electrolysis. Aiming to increase the efficiency of this process, we have developed effective electrode, such as platinum and yttria stabilized zirconia (Pt-YSZ) compound. In this study, we developed new two types of electrode containing cerium oxide (Ceria). One electrode has a double-layer structure used ceria as an inner layer and Pt-YSZ as an outer layer. The other electrode used the ceria as an additive element of Pt-YSZ electrode. Both electrodes show a higher performance than that of Pt-YSZ. Especially, the double layer electrode shows three times higher efficiency than that of Pt-YSZ electrode. In the comparison between Pt-YSZ electrode and the new electrodes, the characteristics of both the electrodes, such as impedance and a structure, were also studied.