Electrolysis of burnup-simulated uranium nitride fuels in LiCl-KCl eutectic melts

模擬照射済みウラン窒化物燃料の溶融塩電解

佐藤 匠  ; 岩井 孝; 荒井 康夫

Sato, Takumi; Iwai, Takashi; Arai, Yasuo

本研究は、窒化物燃料の乾式再処理技術開発に資するため、代表的な固体核分裂生成物であるMo, Pd, Ndを添加した模擬照射済みUNペレットのUClを約0.54wt%含む溶融LiCl-KCl共晶塩中、773Kにおける電解挙動を調べた。サイクリックボルタンメトリーの結果より、いずれの試料も単体と同じくAg/AgCl参照電極に対して約-0.75Vよりも貴の電位で陽極溶解した。この結果をもとに-0.65-0.6Vの陽極電位で定電位電解を行った結果、いずれの試料もUは大部分が溶解し液体Cd陰極中に回収されたが、Mo, Pdは溶解せずに陽極に残留し、Ndは溶解後溶融塩中に残留した。

The electrochemical behavior of burnup-simulated uranium nitride fuels containing representative solid fission product elements, UN+Mo (Mo = 2.84wt%), UN+Pd (Pd = 4.6wt%) and (U,Nd)N (NdN = 8.0wt%), was investigated in the molten LiCl-KCl eutectic salt with 0.54wt% UCl in order to clarify the effect of fission products on the dissolution of actinide nitrides and behavior of FPs in the electrorefining process of spent nitride fuel. The electrochemical dissolution of UN began at about -0.75 V vs. Ag/AgCl reference electrode in all samples as well as that of pure UN. After the electrolyses at the constant anodic potential of -0.65 -0.60 V vs. Ag/AgCl, most of UN was dissolved into LiCl-KCl as UCl at the anode, and U was recovered in the liquid Cd cathode in all samples. Further, Nd was dissolved at the anode and accumulated into LiCl-KCl as NdCl, while Mo and Pd were not dissolved but remained at the anode.