Mineralogical-Geochemical Properties of Bentonite Clays of the Cherkasy Deposit to Increase the Environmental Safety of Radwaste Disposal at the Vektor Storage Complex

Abstract

AbstractThe lack of comprehensively developed and approved in accordance with the established procedure evidence-based requirements for application of clays as a barrier material poses risks for the safe disposal of radioactive waste in storage facilities at Industrial Complex “Vector” for the period of their operation and closure. The bentonite clay from the Ukrainian largest Cherkasy bentonite and palygorskite clay deposit is considered to be the most acceptable as the main component of the insulating screens in radioactive waste storages. The main properties and features of the composition of the Cherkasy natural bentonite clay (Dashukivka site, II layer) and its variety—alkaline earth bentonite (soda-modified bentonite) that provide the radioactive waste isolation in the storage facilities have been considered. The bentonite clays from the Cherkasy deposit were shown to have good waterproofing and barrier properties, including high sorption capacity of 90Sr and 137Cs—one of the main characteristics ensuring safe disposal of radioactive waste. Alkaline earth bentonite adsorbs 90Sr and 137Cs more efficiently than the natural one. However, 90Sr is adsorbed in greater amounts than 137Cs on both types of bentonite. When the time of interaction with an aqueous solution increases, both types demonstrate redistribution of mobile (exchangeable) and immobile (non-exchangeable) forms of radionuclides. The portion of the immobile form, which does not participate in the migration processes, increases.KeywordsBentoniteCherkaske depositIsolation propertiesCaesiumStrontiumSorption