Abstract
Gas generation and migration are important processes that must be considered in a safety case for a deep geological repository (DGR) for the long-term containment of radioactive waste. Expansive soils, such as bentonite-based materials, are widely considered as sealing materials. Understanding their long-term performance as barriers to mitigate gas migration is vital in the design and long-term safety assessment of a DGR. Development and the application of numerical models are key to understanding the processes involved in gas migration. This study builds upon the authors’ previous work for developing a hydro-mechanical mathematical model for migration of gas through a low-permeable geomaterial based on the theoretical framework of poromechanics through the contribution of model verification. The study first derives analytical solutions for a 1D steady-state gas flow and 1D transient gas flow problem. Using the finite element method, the model is used to simulate 1D flow through a confined cylindrical sample of near-saturated low-permeable soil under a constant volume boundary stress condition. Verification of the numerical model is performed by comparing the pore-gas pressure evolution and stress evolution to that of the results of the analytical solution. The results of the numerical model closely matched those of the analytical solutions. Future studies will attempt to improve upon the model complexity and investigate processes and material characteristics that can enhance gas migration in a nearly saturated swelling geomaterial.
Highlights
The primary purpose of a deep geological repository (DGR) for the long-term management of radioactive waste is to contain and isolate wastes to minimize impact to the environment and radiological exposure to people
An important component in the design and long-term safety assessment of a DGR is the longperformance of bentonite seals as barriers against gas migration
As gas generates from the degradation term performance of bentonite seals as barriers against gas migration
Summary
The primary purpose of a deep geological repository (DGR) for the long-term management of radioactive waste is to contain and isolate wastes to minimize impact to the environment and radiological exposure to people. In developing a safety case for a DGR, which provides the supportive arguments that the long-term solution for the management of radioactive waste will be protective of human health and the environment over the long term, relevant features, events, and processes (FEPs), must be evaluated [1,2]. One such process with the potential means for radiological exposure to the biosphere is the generation of radioactive gas which may migrate to the surface [3]. This task, led by the British Geological Survey (BGS), further attempts to identify the physical HM mechanisms required to adequately model dilatancy-controlled gas migration
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