Temperature Dependence of the Sorption and Distribution of Cs, Sr, and Am on Fractured Rock Minerals of the Nizhnekansky Massif

The heat generation by high-level waste raises the temperature in the near-surface zone of the repository, and the effect of this factor on the behavior of radionuclides in the host fractured rock environment upon deep disposal of radioactive waste (RW) should be considered in predictive modeling. The sorption behavior and spatial distribution of Cs, Sr, and Am on the surface of a fractured rock sample of the Nizhnekansky massif depending on temperature were studied. The distribution coefficients of Sr and Am on the sample surface increase with increasing temperature from 25 to 70°C, whereas the Cs distribution coefficient does not increase. This difference may be associated with different mechanisms of the sorption of these radionuclides. Cs, Sr, and Am are nonuniformly distributed on mineral phases of the fractured sample and are preferentially retained on Ca(Sr)-zeolite forming the mineral composition of the fractures. The coefficients of the phase distribution of radionuclides on separate mineral phases/associations were determined by quantitative analysis.