Key components of the repository
This design will continue to evolve as the project progresses and will adapt to changes in technology and future decisions about nuclear power generation that may change the volume or type of fuel to be managed.
For example, in Canada, there is an active research sector exploring new technologies such as small modular reactors (SMRs), fuel reprocessing and other types of advanced reactors. New nuclear technologies may result in different types of used fuel. However, there is international consensus that deep geological repositories represent the best practice for the long-term management of used nuclear fuel resulting from SMRs as well, including any high-level waste from reprocessing.
The repository design is currently sized to account for the existing inventory of used fuel, as well as projected inventories from planned reactor life extensions and refurbishments of operating reactors. Both potential sites have the capability for expansion of the underground to accommodate additional inventory. For more information about how the NWMO will account for the potential for used fuel created by SMRs, please see the section Keeping abreast of the external landscape and adapting to change.
The deep geological repository uses a multiple-barrier system designed to safely contain and isolate used nuclear fuel over the very long term. Constructed more than 500 metres below ground, the repository will consist of a network of placement rooms that will store the used nuclear fuel. This approach aligns with international best practices.
At the surface, there will be facilities where the used fuel is received, inspected and repackaged into purpose-built containers encased in a buffer box of bentonite clay before being transferred to the main shaft for underground placement. Work is underway on the design of the repository surface facilities, including the Used Fuel Packaging Plant.
The repository underground will be accessed through three shafts, which will be located within a single centralized and secure services area. This services area will also include an underground demonstration facility for initial testing of the future engineered barrier emplacement equipment. The layout also includes multiple access tunnels that enable the placement rooms to be situated in areas with the most suitable host rock. The buffer boxes, with the used fuel containers inside, will be arranged in the horizontal placement rooms, and any spaces left over will be backfilled with granular bentonite pellets or chips.
In 2022, we successfully completed a full-scale demonstration of the engineered barriers that will safely contain and isolate Canada’s used nuclear fuel in a deep geological repository. This important safety and technical achievement was the culmination of more than eight years of preparation, including the design and fabrication of specialized prototype equipment and components by the NWMO’s team of leading technical specialists and engineering partners.
Work has started on site-specific conceptual designs of the repository layout based on information from geoscience assessments and borehole drilling in the potential siting areas. The NWMO will be completing assessments of site-specific transportation systems and developing the preliminary design of the Used Fuel Transportation System. We will continue to evolve the design of the repository using the site-specific information we obtain from additional site characterization after site selection, with an objective to develop the updated repository design for the construction licence around 2030. The proposed site in the WLON-Ignace area would be located in crystalline rock, while the proposed site in the SON-South Bruce area would be in sedimentary rock.