Marinich O. The impact of geological-geochemical conditions of uranium mill tailings dams on migration ability of radionuclides 226Ra, 210Pb та 210Po

The dissertation is devoted to the study of impacts of geological-geochemical conditions taking place in uranium mill tailings dams of the former Production Association "Prydniprovsky chemical plant" on migration ability of natural occurring radionuclides 226Ra, 210Pb та 210Po. The contents of labile 226Ra, 210Pb і 210Po in PCP tailings were determined using sequential extraction procedure. It was determined that the presence of gypsum in tailings leads to significant decrease of labile 226Ra, 210Pb і 210Po contents. The new data of mineralogical and chemical composition of uranium milling tailings was obtained. The composition of PCP tailings is complicated with foreign materials (wastes of other origin) as well as occurrence of tailings of different uranium ore types that resulted in different geochemical and physiochemical conditions in tailings dams. The main geochemical factors of PCP tailings that affect the migration ability of 226Ra, 210Pb і 210Po were determined. The predominant migration of separate radionuclides from tailings to groundwater depending on acid-base conditions was detected using nonequilibrium isotope method. The parameters of actual and forecasting removal of 226Ra from tailings to geologic environment were calculated. The recommendations for ecological safety improvement of PCP tailings were suggested.