The object of this study is the tailings storage facility (TSF) for low-level radioactive waste at the Novosibirsk Chemical Concentrates Plant (NCCP) and the adjacent territory. Liquid low-level waste is discharged via a pipeline into the TSF impoundment. The impoundment is confined by a filtration-type embankment dam constructed from local soils containing uranium ore sludge. Water infiltrates through the walls and base of the impoundment, becoming enriched with radionuclides, and subsequently enters groundwater and surface watercourses.
Investigation of the speciation of radioactive elements is essential for improving the radioecological situation through the development of measures to reduce their migration intensity.
Water samples were collected during the summer season from 6 surface water points and 3 groundwater points from wells at a depth of 7-9 m. The concentrations of cations were determined using ICP AES and ICP MS. Hydrogeochemical modeling was performed using the «HCh» software package. All studies were carried out at the Analytical Center for multi-elemental and isotope research of the Siberian Branch of the Russian Academy of Sciences in 2023-2024.
Physicochemical modeling revealed the speciation of uranium: under oxidizing conditions in surface waters, precipitation of calcium uranate and uranophane occurs, while in subsurface waters characterized by more reducing conditions, uranium oxide precipitates. Additionally, modeling results indicate that uranium is present in aqueous complexes as dicarbonatouranyl and tricarbonatouranyl species.
The calculation results demonstrated that the geochemical conditions of the environment (pH and Eh), along with the uranium concentration controlled by dilution processes, are the primary factors governing the redistribution of uranium in the system with increasing distance from the tailings storage facility. The obtained results contribute to understanding the current radioecological situation in the vicinity of the NCCP low-level radioactive waste tailings storage facility.
