Electrochemical Nucleation and Growth of Uranium and Plutonium from Molten Salts

Abstract

This work examines the nucleation and growth behavior of uranium and plutonium from molten LiCl-KCl eutectic on inert electrodes using electrochemical techniques. Current-time transients obtained from chronoamperometric experiments were compared with theoretical models to characterize the type of nucleation (progressive or instantaneous) for deposition of U and Pu, and co-deposition of U-Pu, from molten LiCl-KCl at inert electrodes. It was established that the nucleation mode of actinides present as chlorides in molten chloride salts changes from progressive to instantaneous with an increasing concentration of the trivalent actinide ions in the salt. The effect of the material of the working electrode was investigated, and it was found that changing the material from tungsten to silver improves resolvability of the nucleation peaks and allows more accurate analysis of the experimental measurements. Using the nucleation data, diffusion coefficients were obtained for U3+ and Pu3+, and were found to be in very good agreement with the values obtained from other studies. The density of nuclei produced during instantaneous nucleation, the rate of nucleation for progressive nucleation, and the radius of the deposited nuclei were evaluated and examined at different overpotentials.