Anodic behaviour of a metallic U-Pu-Zr alloy during electrorefining process

電解精製工程におけるU-Pu-Zr陽極挙動

村上 毅*; 坂村 義治*; 秋山 尚之*; 北脇 慎一 ; 仲吉 彬  ; 福嶋 峰夫 

Murakami, Tsuyoshi*; Sakamura, Yoshiharu*; Akiyama, Naoyuki*; Kitawaki, Shinichi; Nakayoshi, Akira; Fukushima, Mineo

電解精製工程は、金属燃料(U-Zr, U-Pu-Zr)の乾式再処理の主要な工程の一つである。電解精製工程では、アクチナイドの高い回収率を達成するために、陽極中のアクチノイドを一部のZrとともに溶解する。しかし、Zrの溶解は乾式再処理工程に問題を起こす。そのため、未照射U-Pu-Zrを陽極に用いて、Zrの溶解量を最小限にした電解精製試験を773KのLiCl-KCl-(U, Pu, Am)Cl塩中で行った。実験では、Zrの溶解電位よりも卑な電位(1.0V vs Ag/Ag)で、Zrの溶解量を制限して実施した。ICP-AESによる陽極残渣中の元素分析の結果、U及びPuの高い溶解率(U; 99.6%, Pu; 99.9%)が達成されたことを確認した。

An electrorefining is one of the main steps of pyrochemical reprocessing of spent metallic fuels (U-Zr, U-Pu-Zr). The electrorefining is carried out dissolving a portion of Zr together with actinides to accomplish a high dissolution ratio of actinides. However, the electrorefining with Zr co-dissolution should bring some practical problems in the pyrochemical reprocessing. Therefore, electrorefining tests of non-irradiated U-Pu-Zr alloy were performed with minimizing the amount of Zr dissolved in LiCl-KCl-(U, Pu, Am)Cl melts at 773 K. The tests were performed both by potentiostatic electrolysis at -1.0 V (Ag/Ag) that was more negative than the Zr dissolution potential and by galvanostatic electrolysis with a limited amount of Zr dissolution. The ICP-AES analysis of the anode residues confirmed that a high dissolution ratio of actinides (U; 99.6%, Pu; 99.9%) was successfully demonstrated at both electrolyses.