High-temperature interaction of components of spent uranium nuclear fuel with alkali metal carbonates in the course of voloxidation in the Carbex process

Interaction of UO2, U3O8, ZrO2, Nb2O5, CeO2, Ce2O3, Pr6O11, Eu2O3, Yb2O3, Tb7O12, and Re metal with lithium, sodium, and potassium carbonates in the temperature interval 300–900°С was studied using methods of thermal analysis and X-ray diffraction. The major products of the high-temperature reactions are alkali metal uranates and diuranates, and in the case of ZrO2, Nb2O5, and lanthanide oxides, oxides of metals in higher oxidation states and salts of the corresponding metal-containing acids, formed by reactions of the oxides with sodium carbonate.