高放废物处置库非饱和多场耦合数值模拟与参数分析

为对高放废物处置库进行安全评估,建立了岩土材料饱和非饱和的渗流温度应力(THM)多场耦合数值模型,对处置库(处置容器、缓冲材料和围岩)进行非饱和THM多场耦合数值模拟。基于COMSOL Multiphysics软件平台,以北山花岗岩高放废物处置库和内蒙古高庙子膨润土为研究对象,对高放废物处置库进行长达500a的数值模拟,对比分析耦合与非耦合的模拟结果,并对渗透率、导热系数和地下水深度等参数进行敏感性分析。结果表明:耦合模拟的温度比非耦合模拟的温度低13℃；地下潜水面由0m上升到1000m的时候,缓冲材料完全饱和的时间由703a下降到了28a；围岩的固有渗透率下降5个数量级时,缓冲材料的饱和时间由28a上升到了250a；各个物理场相互耦合,共同影响处置库的长期稳定性。

Unsaturated multifield-coupled numerical simulation and parametric analysis for geological repository of high-level radioactive waste

In order to evaluate the safety of the repository (disposal container, buffer material and surrounding rock), an unsaturated Thermo-Hydro-Mechanical (THM) fully coupled numerical model was built to conduct the unsaturated multifield-coupled numerical simulation. Based on the Comsol Multiphysics platform, the high-level radioactive waste repository was simulated for 500 years, with the basis of experimental data from the candidate area of the Beishan high-level radioactive waste repository in China and the Gaomiaozi bentonite. Results of the coupled simulations were compared with those of uncoupled simulations, and the parametric sensitivities of permeability, heat transfer coefficient and underground water depth were analyzed. The results show that temperature in coupled simulation is 13 degrees Celsius higher than that in uncoupled simulation. When the water table rises from 0 m to 1,000 m, the time it takes to fully saturate the buffer material will fall from 703 to 28 years. The saturation time of the buffer material will increase from 28 years to 250 years when the permeability of the surrounding rock decreases by five orders of magnitude. Each physical field is coupled to each other, which affects the long-term stability of the repository.