INFLUENCE OF ZIRCONIUM AND NIOBIUM ON CATHODIC DEPOSITION OF URANIUM-DIOXIDE FROM ALKALI CHLORIDE MELTS

Electrocrystallization of uranium dioxide from molten chloride electrolytes in the presence of zirconium(IV) and niobium(V) was studied by voltammetry. Zirconium(IV) was found to react with uranium dioxide according to exchange mechanism to form (1 - x) UO2 . xZrO(2) solid solutions. Niobium(IV), a product of cathodic reduction of niobium(V), enters into the exchange reaction with uranium dioxide to yield (1-y) UO2 . yNbO(2) solid solutions. In the case of simultaneous presence of Nb(V) and Zr(IV) in electrolyte, ternary (1-x-y) UO2 . xZrO(2) . yNbO(2) solid solutions are obtained at the cathode surface. Nucleation of the solid solutions phase was shown to occurs at the most active sites of the crystalline precipitate of uranium dioxide.