Abstract
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.
Highlights
Nuclear energy has been widely used as a clean and efficient energy resource
Cesium-133 is the only stable isotope found in nature, and the remaining radioactive isotopes are produced by uranium fission [7]. 137 Cs has a long half-life of 30.5; active Cs exhibits medium and high-level radiotoxicity
This study aims to establish whether the hydration reaction of the magnesium silicate hydrate (M–S–H) gel system changes with the addition of Cs+, and to clearly determine the leaching effect of the M–S–H cement on Cs+, compared with that of the ordinary Portland cement (OPC) system
Summary
Nuclear energy has been widely used as a clean and efficient energy resource. Despite the considerable economic and social benefits of nuclear energy, the problem concerning the large amount of nuclear waste to be disposed of requires global attention [1,2,3]. A total of 34 cesium isotopes have been found, including 137 Cs and 134 Cs. A total of 34 cesium isotopes have been found, including 137 Cs and 134 Cs Among these isotopes, cesium-133 is the only stable isotope found in nature, and the remaining radioactive isotopes are produced by uranium fission [7]. 137 Cs is highly active and typically exists in the form of ions. Cesium-133 is the only stable isotope found in nature, and the remaining radioactive isotopes are produced by uranium fission [7]. It can migrate in soil and water and cause radioactive pollution when entering an environment with groundwater [8,9,10]. Inert Cs (e.g., CsCl) instead of active Cs is often used to avoid radiotoxicity [6,7]
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