Geological disposal of high-level radioactive waste (HLW) is considered the most feasible way to isolate waste from the sphere of human life. It is essential to predict the coupled thermo-hydro-mechanical-chemical (THMC) effect on the disposal system under the deep depth condition to secure the safety of the disposal system. Especially numerical simulation is an effective method for evaluating long-term behavior. We performed a series of numerical simulations to model the THM coupled behavior of the Full-scale Emplacement (FE) experiment as a part of Task C in the DECOVALEX-2023 project. We compared the numerical simulation results using OGS-FLAC to the field data, including pore pressure, relative humidity, temperature, displacement, and stress at the bentonite and host rock, considering the ventilation process. The capillary pressure was the dominant factor in the flow of the buffer system, and we observed thermal-induced pressurization in the far-field host rock.
High-level radioactive waste has high toxicity and a long half-life of up to thousands of millions of years. Therefore, it is crucial to isolate the HLW waste from the biosphere securely, and geological disposal is considered the most feasible way.
The geological disposal system consists of the engineered barrier system (EBS), including a canister and bentonite, and the natural barrier system (NBS), the host rock. EBS and NBS have a role in delaying the possible nuclide migration from the waste. Hence it is essential to comprehend the thermo-hydro-mechanical-chemical (THMC) coupled interactions induced by the disposal system components to maintain the barrier system performance for a long period.
Various studies have been performed to investigate the coupled behavior, and numerical simulation has the advantage of cost-effectiveness and long-term behavior prediction of the disposal system.
DECOVALEX is one of the most famous international cooperative projects to develop numerical methods and models validating with test results to predict THMC interactions in the disposal system. DECOVALEX-2023 consists of 7 tasks, and among them, Task C aims to model the Full-scale Emplacement (FE) experiment at Mont-Terri underground research laboratory (URL) to develop numerical methods for THM coupled interaction.
