[en] The long-term safety and performance of a Deep Geological Repository for used nuclear fuel will rely, in part, on the integrity of the geosphere barrier enclosing the repository. The purpose of this report is to present an illustrative case study intent on providing a bounding thermal-mechanical-hydraulic estimate of repository and geosphere response and evolution during excavation, operations and post-closure phases. The analyses consider the Mark II (48 bundle) canister design and repository configuration in crystalline and sedimentary rock settings at a nominal depth of 500 m below ground surface. On a timeframe of 1 million years (1Ma), a period relevant to the demonstration of repository safety, the influence of time dependent material properties and varied repository loading conditions are simulated. These include longterm rock mass strength degradation, thermal loading generated by canister heat flux, glacial ice-sheet advance and retreat, rare and extremely strong earthquake ground motions, internal repository gas pressure generated by canister corrosion, and transient hydraulic formation pressures. The analysis conducted is focused at the scale of the canister placement rooms and repository panels. Results provide time series estimates of overall repository stability during 1Ma that, among other factors, provide quantitative estimates of rock mass deformation and damage, evolution of the Excavation Damage Zone (EDZ), and the hydraulic and mechanical loading of a used fuel canister. In order to conduct the analyses a number of assumptions were applied to explore and test notions of geosphere and repository stability and resilience to future loading. These included: 1) Hydraulic Formation Pressures: A hydrostatic formation porewater pressure of 5 MPa was assumed for the repository at 500 m depth; 2) Long-term Rock Mass Strength: Time dependent rock mass strength degradation was simulated with the long-term rock mass strength set to 40% of Unconfined Compressive Strength (UCS). This long-term rock mass strength is equivalent to the crack initiation stress; 3) Temperature Evolution: The emplacement room geometry and layout is designed to ensure the maximum used fuel canister surface temperature remains less than 100°C; 4) Glaciation: Transient glacial ice-sheet history and loading were explicitly considered with maximum ice-sheet thicknesses approaching 3 km; iv 5) Earthquakes: Rare and strong ground motions (i.e., 0.5g) associated with long return period (1Ma) earthquakes were simulated; 6) Repository Gas Pressures: Gas generation within the repository as a result of corrosion yields a maximum pressure of 8.3 MPa; 7) Effective Stress Formulation: Effective stress calculations were estimated without considering pore pressure relief in the low porosity rocks; 8) Joint Strength: Pre-existing joints within a crystalline rock mass were assumed to be cohesionless with a relatively low friction angle of 30°; and 9) Thermal Expansivity: Relatively high coefficients of thermal expansion were applied to yield bounding estimates of rock mass damage. For both sedimentary and crystalline settings rock mass damage will occur as a result of: i) transient changes in in-situ stress magnitude and orientation; ii) thermally-induced stress changes; and iii) time-dependent rock mass strength degradation. It is evident from the analyses that damage is primarily driven by thermally-induced stress changes occurring within approximately 1,000 years of repository closure. Glacial ice-sheet loading and strong earthquake ground motion do not materially influence rock damage. The bounding long-term rock mass strength of 40% UCS does not yield significant damage and, in this case, it is evident that the engineered backfill provides confinement that mitigates spalling, fracture dilation, and likely contributes to slowing the rate of time-dependent strength degradation. Displacements are uniform and relatively small not exceeding 40 mm. During glaciation maximum displacements are estimated not to exceed 12 mm. The EDZ is predicted to extend not more than 1 to 3 meters into the enclosing host rock formation from excavated surfaces. For this illustrative case study, the maximum loading of used fuel canisters for the sedimentary and crystalline scenarios is predicted to be 22.7 and 29.8 MPa, respectively. A detailed explanation of the above findings and unique aspects related to sedimentary and crystalline environs is provided herein. (author)