(418a) Electrochemical Deposition of Sr and Ba into Liquid Bi from Molten Salt Electrolytes

Electrochemical deposition of Sr and Ba into liquid Bi metal was investigated in LiCl-KCl-SrCl₂-BaCl₂ electrolytes at 500 °C as a means to separate stable alkaline-earth ions from the eutectic LiCl-KCl utilized for recycling used nuclear fuel, by leveraging the strong chemical interactions between alkaline-earth metals and liquid Bi. The liquid Bi electrodes were subjected to cathodic discharge in eutectic LiCl-KCl with the addition of 5 mol% total of SrCl₂ and/or BaCl₂. The use of Bi resulted in co-deposition of Sr (2.0–6.5 mol%), Ba (4.1–12.8 mol%), and Li (5.9–16.2 mol%). The observed co-deposition was supported by thermodynamic analyses of electrode potentials by incorporating the experimentally determined activity values of each alkali/alkaline-earth metal in Bi. Furthermore, the contents of SrCl₂ or BaCl₂ in the electrolyte was varied from 5 to 0.1 mol% to observe the lower limit of alkaline-earth salt composition required to deposit Sr or Ba. The results of this work suggest that alkaline-earth fission products accumulated in molten salts (Sr²⁺ and Ba²⁺) can be recovered into liquid Bi by electrochemical separation, which could be employed as a critical step for recycling the process salt (LiCl-KCl) in order to minimize the generation of additional nuclear wastes.