URANIUM BEHAVIOR DURING THE FORMATION AND SUBSEQUENT STORAGE OF SOLID RADIOACTIVE WASTES FROM CONVERSION PRODUCTION

Abstract

A complex of physicochemical studies of solid radioactive wastes (RW) of the near-surface storage facility from conversion uranium production was carried out. It has been established that the composition of the wastes is represented mainly by calcium compounds: gypsum, calcite, and calcium fluoride. Uranium is distributed throughout the entire volume of wastes. At the same time, uranium is unevenly concentrated along the depth of the sludge. The content of uranium in the wastes is 0.005-0.65 wt. %. Uranium was predominantly adsorbed on the surface of sludge by main components during the formation of the wastes solid phase. Uranium was partially precipitated in the form of calcium-containing weeksite Ca2(UO2)2(Si2O5)3·10H2O, uranophane-alpha Ca(UO2)2(SiO3OH)2·5H2O, and urankalcarite Ca(UO2)3CO3(OH)6·3H2O. The isotopic composition of uranium contained in the storage wastes corresponds, within the error, to the normal isotopic composition of natural uranium. Near-surface storage is constantly exposed to natural factors. Infiltration of atmospheric condensation leads to leaching of some components from solid RW. At the same time, uranium goes into solution in the form of [(UO2)2CO3(OH)3]-, [UO2(CO3)2]2-, [UO2(CO3)3]4- and Ca2UO2(CO3)3. The subsequent migration of uranium with infiltrating water contributes to its distribution within the entire sludge field, including the reclamation soil layer and the near-surface pond. In some areas of the storage facility, the uranium content in the reclamation soil layer reaches 0.043 wt.%. The concentration of uranium in the pond was 17.97 mg L-1. The chemical composition of the pond water was characterized by a high content of chloride-ions (1.29 g L-1), calcium (630 mg L-1), sulfate-ions (224 mg L-1), hydrocarbonates (122 mg L-1). The pond is connected to groundwater, which increases the risk of pollutants escaping beyond the storage facility. For citation: Skripchenko S.Yu., Titova S.М., Nalivaiko K.A., Semenishchev V.S. Uranium behavior during the formation and subsequent storage of solid radioactive wastes from conversion production. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 77-86. DOI: 10.6060/ivkkt.20246705.6925.