Sorption-Reagent Method in Liquid Radioactive Waste Management

Abstract

ABSTRACTMethods of liquid radioactive waste (LRW) decontamination from radionuclides including their co-precipitation at specific conditions or adsorption on selective sorption materials are well known and extensively used in LRW management technologies. At the same time, it was shown in a number of papers that some forms of organic and inorganic ionexchangers react with solutions containing specific components that results in formation of virtually insoluble precipitates inside the sorbent matrix or on its surface. Here in some cases the sorbent selectivity to some radionuclides increases substantially.The sorption-reagent materials synthesized for decontamination purposes are the most highly selective in regard to such difficult to remove radionuclides as strontium-90 and cobalt-60. It was shown by comparative analysis of radionuclide removal efficiency by traditional selective sorbents and developed sorption-reagent materials that the latter have the highest distribution coefficients in systems too complex for “pure” sorption/ion-exchange decontamination. For example, the sorption-reagent materials have strontium distribution coefficients several dozens higher than those of commercially available sodium titanates and silicotitanates.The mechanism of radionuclide sorption on sorption-reagent materials of different types was studied. It was shown that this is a multi-stage process and the course of different stages of chemical reactions and sorption is determined by the parameters of medium from which radionuclides are sorbed. It was also shown that these materials application in liquid radioactive waste management enables one to develop simple technological setups combining the advantages of sorption and precipitation methods.One of the main fields of the sorption-reagent materials application can be decontamination of high-salinity radioactive waste formed whether as a result of ionexchanger filters regeneration in LRW management systems or in reverse osmosis installations. Use of sorption-reagent materials for high-salinity waste management enables one to reduce several ten-fold or even hundred-fold the volume of solid radioactive waste (SRW) to be sent for final disposal and, therefore, to decrease the cost of LRW management. The approach consisting in combined application of reverse-osmosis and sorption-reagent methods for LRW decontamination is suggested.