Influence of the electrolysis conditions and composition of electrolytes in the M2WO4-M2W2O7-UO2WO4 system (M = Li, Na, K, Cs) on the oxygen coefficient of uranium oxide

The oxygen coefficient (O/U atomic ratio) of the cathodic product prepared by potentiostatic electrolysis of tungstate melts was studied in relation to the electrolyte composition, deposition potential, temperature of electrolysis, and cation of the solvent salt. With increasing temperature, the oxygen coefficient of the cathodic product increases. With shifting the deposition potential toward more negative potentials, with increasing concentration of W₂O ₇ ^2? anions, and with decreasing concentration of UO₂WO₄ in the tungstate electrolytes, uranium oxides with smaller oxygen coefficients are formed. The oxygen coefficient decreases with increasing radius of the salt cation, other conditions being equal. The abnormal behavior of melts based on Li₂WO₄ is probably due to lower activity of O^2? anions capable to form strong Li₃O⁺ complexes with lithium cations in the melt. The experimental results can be accounted for using the model of the ionic composition of uranyl-containing tungstate melts based on the concepts of complexation and stepwise solvolysis of uranyl ions.