Abstract
The sorption of radionuclides onto cement materials is a very important parameter when considering the release of radionuclides from radioactive wastes. Once the composition or crystallinity of the constituent minerals of a cement material is changed by alteration in the disposal environment, its sorption ability might be affected. In this study, the effect of hydrothermal alteration on the sorption properties of two cement grouts and Calcium Silicate Hydrogels (CSH-gels) is investigated by using the batch sorption technique. In the case of strontium (a model cation) sorption, the distribution ratio for Ordinary Portland Cement (OPC) and OPC/Blast Furnace Slag blended cement (OPC/BFS) decreased as the alteration temperature increased. This is mainly caused by the decrease of sorption onto CSH-gel which is a constituent of cement materials. In the case of selenium (selenite, a model anion) sorption, the distributionratio decreased as the alteration temperature increased for OPC treated in both distilled water and groundwater, and for OPC/BFS in groundwater. This is attributed to the decomposition of ettringite which sorbs anions. The distribution ratio for OPC/BFS in distilled water increased as the alteration temperature increased, although ettringite decomposed. This is attributed to the formation of monosulphate which also sorbs anions. These results show that the hydrothermal alteration of cement mineral phases in a disposal environment may cause changes which could increase or decrease the sorption of radionuclides onto cements depending on the cement composition and radionuclide speciation.
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Sugiyama, D., Fujita, T. Sorption of Radionuclides Onto Cement Materials Altered by Hydrothermal Reaction. MRS Online Proceedings Library 556, 1123 (1998). https://doi.org/10.1557/PROC-556-1123
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DOI: https://doi.org/10.1557/PROC-556-1123