Modeling of the thermohydromechanical-chemical response of Ontario sedimentary rocks to future glaciations

In this work, the response of a proposed deep geological repository (DGR), located in sedimentary rock formations of southern Ontario, to potential future glaciation cycles is investigated numerically. A coupled thermohydromechanical-chemical model is developed and solved numerically by using the finite element method. The general circulation model (GCM) from the University of Toronto is used to generate future glacial cycles and related surface boundary conditions based on the past 120 000 years of glacial history. The geometry of the hypothetical DGR is adopted from the proposed design. Two types of vertical shaft conditions, effective and failed, are included and investigated in this study. For the case with effective vertical shafts, the results show that the potential radioactive solute transport is diffusion-dominated and the transport distance is contained within natural barriers. However, the results for the case of a shaft seal failure show that future glaciations could potentially lead to significant advection transport of radionuclides from the level of the DGR to the shallow ground water horizons. From a safety perspective, the shaft structure is concluded to be a critical part of the DGR system and needs to be considered as an important factor in safety assessments and future research. (author)