Selective actinides recovery over lanthanides using liquid gallium cathode

液体ガリウム陰極を用いたランタノイドからのアクチノイドの選択的回収

多田 康平  ; 小藤 博英  ; 村上 毅*

Tada, Kohei; Kofuji, Hirohide; Murakami, Tsuyoshi*

Pyroprocessing is a promising technology for a fast reactor cycle with a highly concentrated minor actinides (MA: Np, Am and Cm)-bearing metallic fuel. Separation of actinides (An) from fission products such as lanthanide elements (Ln) is one of the difficult challenges to establish practical pyroprocessing. Liquid Cd cathode (LCC) with LiCl-KCl bath has been generally used for An recovery in our process, however, An/Ln separation performance using LCC was not high enough to fabricate highly concentrated MA-bearing fuel from materials having a high ratio of Ln/An. Our recent studies showed that a combination of liquid Ga cathode with LiCl-KCl bath had potential to give higher An/Ln separation performance, and currently we are developing an innovative pyroprocessing using the liquid Ga electrode. Solubility of U and Pu in liquid Ga is smaller than in liquid Cd. Therefore, the solid precipitates (An-Ga alloy) formation could have a significant influence on designing the process compared to the case of using LCC. However, the influence of the solid precipitates formation on An/Ln separation performance is unclear. In this study, galvanostatic electrolysis test on the recovery of U, Pu and Am in liquid Ga was carried out to investigate the influence. Precipitation of Pu-Ga alloy was observed by SEM/EDX on the cross section of Ga electrode after the electrolysis, and separation factors (SFs) for each metallic elements (M) based on Ce, which is defined as (M/Ce concentration ratio in liquid Ga)/(M/Ce concentration ratio in the salt phase), were calculated to evaluate An/Ln separation performance.