地聚合物固化核素锶反应过程迟滞效应研究

The immobilization of nuclide with in situ transformation with 4A zeolite-based geopolymer is an advanced technic. The “Adsorption-Immobilization ” one-step technic for safety disposal of radioactive wastewater can be realized by that way. Meanwhile, the refinement of this technic calls for the further study of characteristics and mechanism of retardation effect during the geopolymerization. However, the complexity of different stages of geopolymerization makes it very difficult to investigate mechanism impeded by nuclide Sr through experiment independently. The project contains three parts. In the first part, the project aims to study the chemical behavior of Sr and dissolution kinetics of silicon and aluminium from 4A zeolite in high alkalinity environment adjusted by S/L ratio and temperature. The results can deduce the possible reaction mechanism. In the second part, the comparative study of different stages’ characteristics with or without Sr (thermomechanical behavior, electrochemical behavior, macro-properties, micro-properties) can elucidate the retardation effect during the geopolymerization, which can identify the reaction mechanism of retardation effect. In the last part, the leaching behavior of simulated nuclide Sr will be studied combined with the geological environment(pure water, thermal liquid , oxidation environment). The results can be adopted to study the long time stability and safety of solidified body.

“沸石原位转化地聚合物固化核素”可实现中低放射性核废液“吸附浓缩-固化”处置的一体化。该工艺的深入研究迫切需要对地聚合物固化核素反应过程的迟滞效应特性和机制进行探讨。而地聚合反应各个阶段交错发生致使目前难以通过实验手段考察核素Sr对各个阶段迟滞效应的特性及机制。本项目通过调节液固比和温度实施阶段控制，研究地聚合反应溶解阶段高碱度环境中Sr的化学行为和沸石硅铝的溶出动力学，探讨Sr造成地聚合反应迟滞的可能反应机制；进而通过对比研究含Sr/无Sr地聚合反应各阶段特性（放热行为、交流阻抗谱、宏观性能和微观结构）的变化，揭示地聚合反应各个阶段迟滞效应特性，验证迟滞效应的反应机制；结合固化体类地质处置环境（纯水体系、热液介质、氧化环境）模拟核素Sr的浸出行为，进一步阐明地聚合反应迟滞效应对固化体性能的影响，为深入研究地聚合物固化体的长期稳定性和安全性提供科学依据。

本项目针对中低放射性核废液的处理提出了“沸石吸附富集核素－地聚合物固化含核沸石”的两阶段处理工艺。地聚合物与含核素沸石组成了双层固化体系。绝大部分核素富集并固定在沸石晶体结构中，同时地聚合物对含核素沸石起到了进一步的物理包裹和固化作用。由于离子交换作用或高碱度环境对沸石结构的侵蚀，少量核素离子进入到地聚合物的无定形凝胶相中，在电荷斥力或引力的作用下延缓了体系中参加反应的阴阳离子的移动速度，造成了地聚合反应的迟滞效应。通过4种溶液体系的浸出实验、耐高温性能和冻融循环实验分析表明地聚合物-含核沸石固化体热稳定性和抗浸出性均优于水泥基材料。高温处理和冻融循环对地聚合物-含核沸石固化体的长期抗浸出性能未产生明显影响。本项目研究成果将为中低放射性核废物的处理提供技术和理论支持。本项目发表论文7篇，其中SCI收录2篇；授权发明专利4项；培养硕士研究生3名。