Behavior of plutonium and americium at liquid cadmium cathode in molten LiCl–KCl electrolyte

Abstract

The effects of the electrochemical conditions on the behavior of plutonium and proper conditions for plutonium recovery at the liquid cadmium cathode (LCC) used in the pyrometallurgical reprocessing were studied by the electrotransport experiments with small, not stirred electrodes. Plutonium was successfully collected up to 7.75 wt% without disturbance by solid phase formation at the surface. Plutonium collected beyond saturation formed intermetallic compound PuCd6 and accumulated at the bottom of the LCC. The cathodic current density adequate for plutonium collection was proportional to the concentration of plutonium in the molten salt. The behavior of americium was reasonably explained by a local equilibrium model between plutonium and americium at the surface of the LCC, although thermodynamic study and quantitative analysis are needed for further understanding. The plutonium collection rate in practical electrorefiner was estimated to be 324 g/h for one LCC by extrapolation of the experimental results.