Impact of Ag on Electrochemical Recovery of UO2 in Molten LiCl-KCl Salt

Abstract

To investigate the effect of fission element Ag on the electrochemical recovery of UO2, the electroreduction mechanisms of Ag+ and kinetic property of Ag+/Ag couple were first studied on W electrode by different electrochemical techniques. The electrode reactions of Ag+ and were found to be one-step and two-step reduction processes, respectively. The exchange current density of Ag+/Ag couple was estimated to be 0.0431∼0.0727 A cm−2 in the temperature range of 723∼798 K by LP technique, and its activation energy was evaluated to be 33.91 kJ mol−1. The deposition products obtained by constant potential electrolysis (CPE) were characterized by XRD and SEM-EDS, which showed the formed Ag and UO2 having pine-branch and micron-scale polyhedral structure, respectively. The influence of Ag+ on the electrochemical behavior of and morphology of UO2 were studied. The deposition potential of Ag+ was close to that of to UO2. The changes of Ag+ concentration and scan rate had no effect on the electroreduction mechanism of CPE was conducted, and the result indicated that UO2 and Ag could be co-deposited. The deposited Ag could change the morphology of recovered UO2.