A Flux Based on the Eutectic MnO–Al2O3 System for the Selective Extraction of Fissile Materials from Diffusion-Contaminated Metal Radioactive Waste by Induction Slag Remelting

In this study, the possibility of extracting over 99% of the fissile materials contained in metal radioactive waste by cold-crucible induction slag remelting is demonstrated. The flux based on the eutectic MnO–Al2O3 composition does not contain compounds used in non-ferrous and ferrous metallurgy that impede the subsequent hydrometallurgical slag processing and contaminate the final product (agents causing corrosion and gelation, as well as neutron poisons). The relatively high manganese–oxygen affinity eliminates the transition of the macrocomponents of the processed steel (iron and chromium) to the oxide phase. It is shown that the main components of the resulting slag (manganese and aluminum oxides) are represented by the acid-resistant phases of corundum and Mn0.89Al2.11O4 manganese spinel structurally similar to the galaxite mineral, while uranium, used as a fissile material dummy, is contained in the form of relatively large inclusions 3–10 μm in size with a composition that corresponds to the UO2 formula, which is amenable to leaching with nitric acid.