Studies on Direct Electrochemical De-Oxidation of Solid ThO2 in Calcium Chloride Based Melts

Abstract

Molten salt based direct electrochemical de-oxidation methods were investigated for the conversion of ThO2 to Th metal in CaCl2 melts at 900 °C. A Fray-Farthing-Chen (FFC) Cambridge process was performed at a constant cell voltage of 3.1 V wherein a cathode of porous ThO2 pellet and a graphite anode were used. The study also explored the feasibility of electro-calciothermic reduction of ThO2 in CaCl2–0.5 wt.% CaO melt. Electrochemical experiments were carried out for different intervals of time to elucidate the reduction mechanism. The cathode products were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray analysis. No Ca-Th-O intermediate phases were observed during the reduction experiments in either process. This indicates that the reduction might occur in a single step viz. ThO2 to Th. The direct electrochemical reduction of ThO2 in CaCl2 based melts at 900 °C was found to be feasible.