高放废物地质处置库缓冲/回填材料的气体渗透问题研究进展

简要回顾和总结了国内外学者对处置库中的气体形成与渗透机制,注气试验装置与试验方法,以及气体渗透特性等方面的研究成果和最新进展。研究表明,深地质处置库运营过程中会由于金属无氧腐蚀等产生以氢气为主的多组分气体,气体在缓冲/回填材料中主要以对流–扩散渗流、黏性–毛细管两相流、局部膨胀通道渗流和沿宏观裂缝渗流等4种机制渗透。为此,各国学者先后研发了恒体积渗透装置、K0渗透装置、等向应力渗透装置和三轴渗透装置等注气试验装置,采用控制注气流量速率法或控制注气压力法开展了大量注气试验,发现缓冲/回填材料的气体渗透率和特征压力等渗透特性均与其物理性质和边界条件等诸多因素有关。考虑到处置库实际运营工况的复杂性,多场(热–水–化–力)多相(固–液–气)耦合条件下的缓冲/回填材料的气体渗透特性研究将是今后的一个重要工作方向。

Advances in gas permeation problems of buffer/backfill materials in high-level radioactive waste geological repository

A brief introduction is given to the findings and the latest advances in the mechanism of gas generation and migration, the testing equipments and methodologies as well as the properties of gas migration. The results show that the hydrogen based multi-component is generated during the operation of the repository, mainly resulting from the anaerobic corrosion of iron. There are four mechanisms for describing the gas migration in the buffer/backfill materials, including the advection-diffusion of gases dissolved in ground-water, visco-capillary two-phase flow, local dilated pathway flow and macroscopic fracture flow. Therefore, gas permeation devices for tests under the constant volume, K₀ confined, isotropic stress and triaxial conditions are successively developed. Numerous gas injection tests are conducted using the gas flow-rate control or injection pressure control methods. It is shown that the gas permeability and characteristic pressures are influenced by many factors, including the physical properties and boundary conditions of the samples tested. Considering the complexity of the operation conditions for the buffer/backfill materials in a deep geological repository, investigations on the gas permeation under multi-field (thermo-hydro-chemical-mechanical) and multi-phase (solid-liquid-gas) coupled conditions should be a very important work to be conducted.