Behavior of diffusing elements from an integrated cathode of an electrochemical reduction process

The electrochemical reduction process for spent oxide fuel is operated in a molten salt bath and adopts an integrated cathode in which the oxides to be reduced act as a reactive cathode in the molten salt electrolyte cell. Heat-generating radioisotopes in the spent oxide fuel such as cesium and strontium are dissolved in the molten salt and diffuse from the integrated cathode. However, the behavior of the dissolved cations has not been clarified under an electrochemical reduction condition. In this work, the reduction potentials of cesium, strontium, and barium were measured in a molten LiCl-3 wt% Li2O salt and their mass transfer behavior was compared with two current conditions on the cell. The concentration changes of the cations in the molten salt phase were measured and no significant differences on the dissolution behavior were found with respect to the current. However, under a continued current condition, the removal of the high heat-generating elements requires more time than the complete reduction of metal oxide due to the slow rate of diffusion.