Electrochemical reduction of UO2 in molten CaCl2 or LiCl

To develop an electrochemical reduction technique for the reprocessing of nuclear fuels, the reduction behavior of UO(2) at the cathode and the anode reactions were investigated in both CaCl(2) and LiCl salt baths. In the CaCl(2) at about 800 degrees C, UO(2) was reduced into metal over the potential range < 0.6 V vs the Ca(2+)/Ca. The reduced uranium metal cohered due to the high temperature and a dense metal skin covered the surface of the UO(2) disk sample. It prevented the transportation of oxygen from the inside to the bulk salt and the reduction often stopped with UO(2) remaining inside. A significant underpotential deposition of calcium metal was observed. In the LiCl at 650 degrees C, UO(2) was reduced into metal over the potential range < 0.15 V vs the Li(+)/Li. The UO(2) disk sample was satisfactorily reduced because the LiCl melt could permeate into the sample. The current efficiency of UO(2) reduction in the LiCl was much better than in the CaCl(2). The anodic currents for oxygen and carbon oxide gas evolutions were verified in cyclic voltammograms of the platinum and glassy carbon electrodes. At the platinum surface, Pt(3)O(4) and Li(2)PtO(3) yielded in the CaCl(2) and LiCl, respectively. (c) 2006 The Electrochemical Society.