Dissolution of Actinide Oxides in Carbonate Solutions

The dissolution step of uranium and mixed oxide uranium-plutonium spent nuclear fuel is a key initial step of a new alternative hydrometallurgical method—the CARBEX process. The study considers carbonate oxidizing systems NaHCO₃/Na₂CO₃–H₂O₂/2Na₂CO₃·3H₂O₂/M₂S₂O₈, where M = Na⁺, K⁺, or NH₄⁺, for dissolving actinide oxide powders. The chemical and physical factors that determine the rate of oxidative dissolution of powdered individual oxides UO₂, U₃O₈, PuO₂ and NpO₂ in carbonate media were found. The results obtained are important for the development of the oxidative and sonochemical options of dissolution of highly calcined crystalline samples of uranium, plutonium and neptunium oxides, as well of spent nuclear fuel in carbonate media.