Electrochemical Drawdown of U3+ and Ce3+ in Molten LiCl-KCl Using a Liquid Cadmium Cathode

Abstract The electrorefining of spent nuclear fuels is a key step to recover uranium and transuranium on separated cathodes. However, the electrolyte salts become contaminated with fission products after batches of electrorefining, and therefore the two unit processes for the drawdown of actinide and lanthanide are suggested before treatment of the contaminated salts. We investigated the electrochemical drawdown of U3+, Ce3+, and U3+ from Ce3+ in molten LiCl-KCl electrolyte using a liquid cadmium cathode (LCC) at 773 K. The drawdown mechanism of U3+ and Ce3+ was determined by cyclic voltammograms and calculating the equilibrium potential. After galvanostatic electrolysis, high recovery yields were obtained for the drawdown of U3+ and Ce3+, but the current efficiency of Ce3+ was at least twice as high as that of U3+ due to the cyclic electrolysis of U3+/U4+. Despite significant underpotential deposition of Ce3+ in the LCC, an exceptional separation factor for Ce relative to U reached 84.67 ± 17.13, which was attributed to the formed pure uranium products hindering the subsequent deposition of Ce3+. Moreover, pure uranium products and Ce-Cd intermetallic compounds were characterized by X-ray diffraction and scanning electron microscope coupled with energy dispersive X-ray spectroscopy.