Thermo-hydro-mechanical evolution of the engineered barrier system of a deep geological repository

This paper investigates the long-term evolution of the engineered barrier system of a deep geological repository (DGR) for used nuclear fuel in Canada, focusing on coupled thermo-hydro-mechanical (THM) processes in bentonite buffer materials. A fully coupled THM mathematical model was developed, verified against analytical solutions, and validated using experimental data from laboratory and in situ tests. The model was then applied to simulate the near-field response of the EBS within a granitic host rock, focusing on key performance indicators such as temperature distribution, resaturation time, swelling pressure development, and stress on the used fuel container (UFC). The results provide insights into the interactions between thermal, hydraulic, and mechanical processes in the bentonite buffer material, a crucial component in maintaining the repository's integrity. Results indicate that temperature evolution, buffer resaturation, and swelling pressures remain within established safety criteria. Overall, the modeling framework provides a reliable tool for assessing the THM behavior of the Canadian DGR and offers insights into optimizing design parameters to enhance repository safety over extended time scales. These findings contribute to a deeper understanding of the multi-physics interactions governing EBS performance, ultimately supporting informed decision-making in deep geological disposal of nuclear waste.