中国高放废物地质处置缓冲材料大型试验台架和热-水-力-化学耦合性能研究

缓冲材料作为高放废物深地质处置库中一道重要的人工屏障，与高放废物容器和处置库围岩直接接触，在高放废物衰变热、辐射作用和地下水等影响下产生复杂的热-水-力-化学耦合作用，为了验证缓冲材料是否能长期有效地发挥其屏障材料的作用，核工业北京地质研究院利用高庙子钠基膨润土组装并运行了模拟中国高放废物地质处置室 尺寸的大型缓冲材料膨润土试验台架（China-Mock-Up）。建立了缓冲材料试验台架的安装和试验方法，依据实测数据和理论分析，揭示了热-水-力-化学耦合作用条件下膨润土中的相对湿度是在加热器的热效应和外部供水的湿效应共同作用下发生变化的，压实膨润土中应力的变化主要是由于膨润土遇水膨胀和加热器的热效应引起的，试验验证了模拟高放废物地质处置室内加热器（废物罐）运行初期的位移过程，为缓冲材料和高放废物地质处置库的设计提供了重要的工程参数和理论依据。

A large-scale THMC experiment of buffer material for geological disposal of high level radioactive waste in China

The buffer material as one of the most important components of engineered barrier system is the last defence between waste container and host rock. This barrier plays an important role in stabilizing the repository excavations under the coupled thermal-hydro-mechanico-chemical (THMC) conditions, and in providing low permeability and diffusivities, and long-term retardation. To guarantee the long-term safety of the engineered barrier, a large-scale mock-up facility, named China-Mock-up is constructed in the laboratory of BRIUG. This facility concentrates on the research on Gaomiaozi-Na-bentonite, which is currently considered as the candidate buffer and backfill material for China's high level waste (HLW) repository. Methods of construction and test for buffer material Mock-Up is established. The current experimental data of the facility are reported and analyzed in the paper. The saturation process of the compacted bentonite is influenced by the competing mechanisms of drying effect induced by the heater and the wetting effect by the water penetration. The stress evolution of the compacted bentonite may be influenced by the thermal expansion induced by high temperature and the swelling pressure generated by bentonite saturation. The evolution of displacement of the heater which is to simulate vertical placement of a container with radioactive waste is validated for the first time. The experiment is evaluated THMC processes taking place in the compacted bentonite-buffer during the early phase of HLW disposal and to provide a reliable database for numerical modeling and further investigations of EBS, and the design of HLW repository.