| Description |
Direct electrolytic reduction (DER) of UO2 utilizes a molten LiCl-Li2O electrolyte operating at 650ºC. The productive processes at the cathode are UO2 and Li2O reduction (which is followed by metallothermic reduction of UO2 by Li metal). Non-productive reduction current has been observed that could be attributed to impurities produced from interaction of the salt with water. Cyclic voltammetry (CV) scans of molten mixtures of LiCl containing Li2O, LiOH, and/or Li2O2 indicated that LiOH is the primary cause of reduction current preceding UO2 and Li2O reduction. The LiOH reduction appears as a broad soluble-soluble transition at about -0.8 V versus Ni/NiO and forms a pre-reduction plateau characteristic of micro-electrode reactions. Introduction of water vapor into LiCl- Li2O verified that LiOH is the chief moisture-based impurity, and suggests that the DER process should not be adversely affected by water contamination levels under 100 ppm. The electrochemical response to LiOH in the salt was lowered with addition of Li0, providing a practical approach to eliminating LiOH from the LiCl-Li2O salt before commencing the DER process. Generation of H2 gas was detected while heating Li0 with LiCl-Li2O-LiOH, consistent with a reaction mechanism in which LiOH reduction causes formation of Li2O and H2. |
