Experimental study on the behavior of americium in pyrochemical process of spent nitride fuels

Hayashi, Hirokazu ; Shibata, Hiroki ; Akabori, Mitsuo; Arai, Yasuo; Minato, Kazuo 

R&D on the transmutation of long-lived minor actinides (MA) by the accelerator-driven system (ADS) using nitride fuels is underway at JAEA. In regard to reprocessing technology, pyrochemical process has several advantages in case of treating spent fuel with large decay heat and fast neutron emission, and recovering highly enriched N. In the pyrochemical reprocessing, plutonium and MA are dissolved in LiCl-KCl eutectic melts and selectively recovered into liquid cadmium (Cd) cathode by molten salt electrorefining. The electrochemical behavior in LiCl-KCl eutectic melts and the subsequent nitride formation behavior of plutonium and MA recovered in liquid Cd cathode are investigated. Electrochemical study of americium (Am) on electrolyses of AmN in LiCl-KCl eutectic melts and nitride formation of Am recovered in the liquid Cd cathode are presented. Electrochemical behavior of Am on anodic dissolution of AmN and recovery of Am into a liquid Cd cathode by electrolyses in LiCl-KCl eutectic melts was investigated by transient electrochemical techniques. Am was recovered as Am-Cd alloy in the liquid Cd cathode, in which AmCd type phase was identified besides Cd phase. The recovered Am was converted to AmN by the nitridation-distillation combined method. These results suggest that the pyrochemical process developed for the nitride fuel cycle is applicable for the nitride fuels containing Am, which is to be used for the transmutation of MA.