Cesium and strontium sorption separation from liquid radioactive wastes and immobilization in geocements

Abstract

One way to immobilize medium-level liquid wastes is to solidify the wastes by cementing [1, 2]. The main drawbacks of this method are the low filling of the cement with radionuclides from the liquid wastes and the large volume of the radioactive products obtained. To solve these problems it is desirable to extract radionuclides from the wastes by sorption followed by inclusion of the sorbent into a water-resistant cement.In the present paper we report the results of investigations of sorption extraction of cesium and strontium from liquid wastes by natural zeolite and immobilization of the radioactive sorbent, using alkaline slag concrete (geocement) [2]. The stability of this material is largely determined by the similarity of the sorbent and the regenerations of the binding system with respect to the elemental composition and cross-linking groups.Inorganic materials, including natural materials, are attracting attention for removal of radionuclides from contaminated water because of their radiation resistance and high sorption characteristics [3, 4], in contrast to synthetic ion-exchange resins which are suitable for extracting radionuclides only from low-salt-content, low-level solutions [5]. The possibility of immobilizing inexpensive sorbents containing low-lived cesium and strontium radionuclides in mechanically strong and waterresistant matrices makes it possible to reduce substantially the volume of radioactive wastes to be buried.The initial materials for the process being developed are the natural mineral clinoptilolite as the sorbent, and the natural and technogenic components of the binding system --granular slag from metallurgical production, clays, and solutions of alkali-metal compounds.Experimental Conditions. The sorption characteristics of clinoptilolite from the Dzegvi-Tedzami deposits were investigated. Model solutions of wastes from nuclear power plants with BBER and RBMK reactors were used together with real solutions from the Main Science Center of the Russian Federation --Physics and Power Engineering Institute with inorganic content up to 200 g/liter and organic content up to 135 g/liter, 134,137Cs, 9~ specific activity up to 7.107 Bq/liter, and nonradioactive strontium and cesium concentrations 2.10 -4 --10 g/liter. The ratio of the sorbent mass (kg) to the volume of the liquid phase (m 3) during investigation of sorption under static conditions was equal to 1:0.2. Sorption under dynamic conditions was studied using 5-10 mm in diameter adsorption columns with 50-550 mm high sorbent layers.

Strontium leaching from municipal waste subjected to incineration

“…The main source of radioactive strontium is nuclear fission (Bogdanovich et al, 1998 ; Mirzoeva et al, 2022 ; Tsukada et al, 2023 ). Out of Sr radioisotopes produced through nuclear fission, 90 Sr is particularly dangerous to humans, with its amount reaching up to 5.8% (Ageeva et al, 2010 ).…”

Approaches to rehabilitation of radioactive contaminated territories

“…Natural aluminosilicates satisfy these requirements; interest and their intensive study are determined by their ion exchange properties and also by the availability of proven deposits in many countries. Natural aluminosilicates and some of their modified products have been successfully used for decontamination of radioactive polluted natural waters and technological solutions, liquid radioactive wastes, and remediation of land under high anthropogenic impact …”