Immobilization of Radionuclide 133Cs by Magnesium Silicate Hydrate Cement

The radionuclide cesium (Cs) was solidified using magnesium silicate hydrate (M–S–H) cement. The influence of Cs+ on the reaction of the M–S–H gel system was evaluated by measuring the compressive strength and microscopic properties of the solidified body. By testing the impact resistance, leaching resistance and freeze–thaw resistance of the solidified body, the immobilizing ability of Cs+ by the M–S–H cement was analyzed. Results indicate that Cs+ only slightly affects the reaction process of the M–S–H gel system, and only slows down the transformation rate of Mg(OH)2 into the M–S–H gel to a certain extent. The M–S–H cement exhibits superior performance in solidifying Cs+. Both the leaching rate and cumulative leach fraction at 42 d were considerably lower than the national requirements and better than the ordinary Portland cement-solidified body. The curing effect of the M–S–H cement on Cs+ is mainly physical encapsulation and chemisorption of hydration products.