The preparation of UO2 by fused salt electrolysis using UO2 or UF4 as starting material

Coarse crystalline uranium dioxide can be prepared by the electroreduction of UO₂Cl₂ or UO₂F₂ dissolved in fused chloride melts. The uranyl compounds are prepared in the melt by the treatment of UO₂ or UF₄ with a gas mixture of hydrogen chloride and oxygen. It is found that moisture accelerates the oxidation of the fluoride. Using the LiCl-KCl system, oxides with a composition ranging from UO_2.000 to UO_2.007 are obtained. The crystal form is affected by the degree of dryness of the melt and in the case of the LiCl-KCl-fluoride system also by the presence of chlorine in the melt. The presence of fluorides in the melt favourably influences the formation of cube shaped UO2 crystals. The oxides have densities varying between 10.85 and 10.98 (25° C).