Diffusion behavior of oxygen in the electro-deoxidation of uranium oxide in LiCl-rich melt

Abstract

The role of oxygen in the electrolytic reduction of uranium oxide in molten salt has received increased attention in recent years. In contrast to solubility, few studies were reported on the kinetic property of oxygen in LiCl. In this work, diffusion behaviors of oxygen anion in the bulk salt and oxide cathode were both studied. A gold working electrode was used to conduct corresponding voltammetry studies in LiCl-rich melt at 923 K. The obtained diffusion coefficient increased when another salt (KCl or LiF) was introduced to LiCl. A model based on ohmic, concentration and electrochemical polarizations was derived and used to describe the electro-deoxidation of uranium oxide in molten salt. By analyzing experimental current-time curves obtained from potentiostatic electrolysis, parameters such as exchange current density, conductivity of porous uranium filled with electrolyte and diffusion coefficient of oxygen anion in porous uranium were calculated. Taken together, the behavior of oxygen in the electro-deoxidation of uranium oxide in LiCl-rich melt can be better understood.