Short-term thermal modelling of a conceptual deep geological repository in Canada

Canada has decided on long-term containment and isolation of used fuel within a deep geological repository. The deep geological repository will be constructed at a depth of roughly 500 m and consist of a network of placement rooms at depth and surface facilities to support the operation of the repository. An engineered barrier system will fill the area between used fuel containers and the geosphere to isolate the used fuel containers from the environment. The engineered barriers will be subjected to competing gradients of thermal energy driving moisture away from the containers and hydraulic gradients driving moisture into the repository. A key thermal design criterion is for the container surface temperature to be less than 100°C. Recently, thermal properties were defined for the barrier materials in the placement room. The effect of barrier material saturation on dissipation of thermal energy for a generic Canadian placement room is examined for upper- and lower-bound scenarios, which are believed to bound the short-term thermal response of the repository under hydraulically static conditions. The results show that the 100°C criterion is met if continuity is maintained between the container and the rock.