Sorption of radionuclides by cement-based barrier materials

This paper investigates the sorption of radionuclide ions, 137Cs+ and 90Sr2 +, by cement-based barrier materials for radioactive waste disposal. A mortar with ternary binder is prepared and powder samples are ground from the hardened material following a predetermined granulometry. After pre-equilibrium with an artificial pore solution, the sorption behaviors of powder samples are investigated through single sorption and blended sorption. The results show that: (1) no systematic difference is observed for single and blended sorptions thus the interaction between 137Cs+ and 90Sr2 + sorptions must be weak; (2) the sorption kinetics is rapid and all characteristic times are less than 1d; (3) the sorption capacity is enhanced by C-A-S-H hydrates and the measured Kd values can be predicted from C-S-H sorption data with Ca/Si ratio equal to Ca/(Si + Al) ratio.