Determination of uranium and rare-earth metals separation coefficients in LiCl-KCl melt by electrochemical transient techniques

塩化カリウム-塩化リチウム共晶溶融塩中のウランと希土類金属の分離係数の電気化学的測定

Kuznetsov, S. A.*; 林 博和 ; 湊 和生 ; Gaune-Escard, M.*

Kuznetsov, S. A.*; Hayashi, Hirokazu; Minato, Kazuo; Gaune-Escard, M.*

使用済み燃料の乾式再処理プロセスの検討では溶融塩中のアクチニドとランタニドの分離係数が重要である。723から823KにおいてUClとLaClを含んだLiCl-KCl共晶溶融塩試料のボルタンメトリを行い、ウランとランタンの還元ピークからそれぞれの式量電位を求め、ウランとランタンの分離係数を導出した。また、Uイオンの拡散係数,U(III)/U(0)電極反応の電子授受速度など速度論的定数を測定した。

The knowledge of separation coefficients of actinides and rare-earth metals is important for developing pyrometallurgical process of spent nuclear fuel. Electrochemical experiments were carried out at 723-823 K to estimate separation coefficients in LiCl-KCl eutectic melt containing uranium and lanthanum trichlorides. Uranium and lanthanum separation coefficients is calcurated with the voltammetric peak potentials of U (III) and La (III), their concentration in the melt and kinetic parameters for U(III) discharge such as diffusion coefficients, and standard rate constants of charge transfer. The diffusion coefficients of U (III) were determined by some electrochemical measurements. The standard rate constants of charge transfer for electroreduction of uranium U(III) +3e =U were calculated by impedance spectroscopy method.