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The behavior of the [16O-U-16O]2+, [16O-U-18O]2+, and [18O-U-18O]2+ isotopic species in uranyl fluoride complexes was studied in isopropanol under pulsed UV irradiation of solutions at λ = 300–400 nm. Illumination of the solutions affects the isotope composition of oxygen in uranyl owing to photoreduction and isotope exchange with the water molecules occurring in the solution. The absorption spectra of the UO2F2 solutions with different isotope compositions of oxygen were measured. The enrichment of UO2F2 in 18O only slightly affects the absorption in solution. The IR spectra show that the content of the [16O-U-18O]2+ species in solution decreases more rapidly than that of [18O-U-18O]2+. Comparison of the photoreduction rates for UO2F2 species with different isotope compositions of oxygen suggests that this effect cannot be attributed to the difference in the quantum efficiencies of photoreduction for different isotopic species. Accelerated decrease in the content of the [16O-U-18O]2+ species in solution under irradiation was attributed to the excitation exchange processes in uranyl fluoride polymers. [ABSTRACT FROM AUTHOR]

Activated structural materials of fusion reactors after the reactor decommissioning may be sent either for burial or for radiochemical reprocessing and consequent material refabrication. This paper considers an opportunity of radiochemical extraction reprocessing of activated vanadium alloy, which is a potential structural material for Russian demonstration fusion reactors (DEMO). The nitrate solutions of the alloy components were used as the aqueous phase. The solution of di-2-ethyl-hexyl-phosphoric acid (D2EHPA) in a hydrocarbon solvent was chosen as an extractant in the experiments. The extraction of alloy impurities (till the dose rate level of 12.5 µSv/h) may be attained in an extractor cascade with 50 stages. End products of the extraction reprocessing are nitrate solutions of vanadium and chromium and titanium hydroxide. The expediency of the radiochemical reprocessing of the alloy or its burial may be determined after the technical and economic comparison of these processes. [ABSTRACT FROM AUTHOR]