The Nuclear Waste Management Organization (NWMO) was established in 2002 by Canada’s nuclear electricity producers in accordance with the Nuclear Fuel Waste Act (NFWA). The NWMO is responsible for implementing Adaptive Phased Management (APM), Canada’s plan for the long-term management of used nuclear fuel. The technical end point of APM is the centralized containment and isolation of the used fuel in a deep geological repository (DGR) located in a stable crystalline shield or sedimentary bedrock formation. The DGR concept comprises multiple barriers to contain and isolate the used nuclear fuel for time frames of 1 Ma. A key component in the DGR concept is the surrounding geosphere, which acts to protect the engineered barrier systems, to preserve a stable environment in which radionuclide migration is minimized, and to create a barrier to inadvertent intrusion. At a depth of approximately 500 m, the ability of the geosphere to act as a natural barrier is governed by site-specific features and attributes.
The NWMO is pursuing an active geoscience program into the long-term evolution of crystalline and sedimentary geospheres, which includes collaboration with Canadian and international experts, focused on a wide range of topics related to the development of DGRs for the safe containment of used fuel. The primary objectives in developing geosphere models are to: 1) support site selection and future site characterization activities; 2) advance the understanding of the geosphere in terms of stability, predictability, and resilience to long-term perturbations; 3) substantiate the role of geoscience in establishing support for a DGR safety case; and 4) maintain a high level of competency and a credible Canadian-based technical program. This is achieved through the development of approaches for evaluating and interpreting geosphere properties, groundwater system behaviour and predictions of long-term geosphere and DGR performance. The evolution of deep-seated groundwater systems in fractured crystalline rock is illustrated in part through the integrated application of fracture network, groundwater, and glacial system modelling.