College of Materials Science and Engineering, Shenzhen University, Shenzhen, 518055, China.
College of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, 518000, P. R. China.
Phys Chem Chem Phys. 2022 Aug 3;24(30):18083-18093. doi: 10.1039/d1cp04164a.
Cesium (Cs) and strontium (Sr) ions are the main fission byproducts in the reprocessing of spent nuclear fuels for nuclear power plants. Their long half-live period (30.17 years for Cs and 28.80 years for Sr) makes them very dangerous radionuclides. Hence the solidification of Cs and Sr is of paramount importance for preventing them from entering the human food chain through water. Despite tremendous efforts for solidification, the long-term stability remains a great challenge due to the experimental limitation and lack of good evaluation indicators for such long half-life radionuclides. Using density functional theory (DFT), we investigate the origin of long-term stability for the solidification of Cs and Sr inside sodalite and establish that the exchange energy and the diffusion barrier play an important role in gaining the long-term stability both thermodynamically and kinetically. The acidity/basicity, solvation, temperature, and diffusion effect are comprehensively studied. It is found that solidification of Cs and Sr is mainly attributed to the solvation effect, zeolitic adsorption ability, and diffusion barriers. The present study provides theoretical evidence to use geopolymers to adsorb Cs and Sr and convert the adsorbed geopolymers to zeolites to achieve solidification of Cs and Sr with long-term stability.
铯 (Cs) 和锶 (Sr) 离子是核电站乏核燃料后处理的主要裂变副产物。它们的半衰期长（Cs 为 30.17 年，Sr 为 28.80 年），因此是非常危险的放射性核素。因此，为了防止它们通过水进入人类食物链，Cs 和 Sr 的固化至关重要。尽管为固化做了巨大的努力，但由于实验限制以及缺乏对这种长半衰期放射性核素的良好评价指标，长期稳定性仍然是一个巨大的挑战。我们使用密度泛函理论 (DFT) 研究了 Cs 和 Sr 在方钠石内部固化的长期稳定性的起源，并确定交换能和扩散势垒在热力学和动力学上都对获得长期稳定性起着重要作用。全面研究了酸度/碱度、溶剂化、温度和扩散效应。研究发现，Cs 和 Sr 的固化主要归因于溶剂化效应、沸石吸附能力和扩散势垒。本研究为使用地质聚合物吸附 Cs 和 Sr 并将吸附的地质聚合物转化为沸石以实现 Cs 和 Sr 的长期稳定固化提供了理论依据。
