Sorption of Cs, Np, and Pu by the rocks of the Yeniseisky site depending on the temperature and ionic strength of Mg-K-phosphate leaching solutions

The study of radionuclide migration is of particular concern in when substantiating safety procedures involved in the deep disposal of radioactive waste in the host rocks of the Yeniseisky site located in Krasnoyarsk Krai. One of the main processes controlling the migration of radionuclides is the sorption by mineral phases of host rocks. The present work aims to obtain quantitative characteristics of ¹³⁷Cs, ²³⁷Np, and ²³⁹Pu sorption by the rocks of the Yeniseisky site under conditions simulating a deep disposal of radioactive waste. The distribution coefficients of ¹³⁷Cs, ²³⁷Np, and ²³⁹Pu were determined depending on the ionic strength and temperature of the solutions after leaching the Mg-K-phosphate compound. Differences in the effect of K⁺ and Mg²⁺ cations on cesium sorption by the rocks were established. At an increase in the temperature, the efficiency of ²³⁹Pu and ²³⁷Np sorption by the rocks increases, while the sorption of ¹³⁷Cs remains almost constant.