Assessing the technical aspects of spent nuclear fuel storage in deep horizontal boreholes

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Nuclear power generation is expected to play an important role in the transition to a low-carbon energy future. This will include the continued use of large-scale power generation plants similar to those used for several decades in various locations, including Canada. However, new opportunities for nuclear power generation are emerging with the advent of small modular reactors (SMRs). The provinces of New Brunswick, Ontario, Saskatchewan and Alberta recently signed a memorandum of understanding which lays out plans to implement a number of SMR designs in the next 10 years. The proposed research will support these plans by developing options for storing spent nuclear fuel in deep horizontal boreholes. The spent fuel resulting from nuclear power generation is radioactive, hence it requires careful management. This spent fuel exists in a solid state, and in some cases may be useful in the future (e.g., for recycling and reuse as reactor fuel). As such, there is a need to place spent fuel in a secure environment from which it may be retrieved for some interval of time, but which will also continue to isolate the spent fuel from the surrounding environment over the long term. Extensive research has been conducted globally on deep geological repositories suitable for long-term storage and disposal of spent nuclear fuel in non-porous rocks like shale, halite (rock salt) or granite. Repository designs planned for imminent use are based on mining and tunneling technologies. The design selected for use in Canada includes a vertical shaft sunk to the desired depth, from which a network of access tunnels and storage rooms are excavated laterally. Two possible sites in Ontario are being considered for this type of repository. The main goal of this research is to develop technologies for secure, long-term storage of spent nuclear fuel in deep geological repositories constructed using horizontal boreholes drilled from ground surface. The research would build on previous research in conventional repository design and the tremendous advancements achieved in horizontal drilling and completion technology in the past 25 years, seeking the best means of combining and adapting these technologies to develop a relatively low cost, flexible, scalable and secure means of storage. The specific objectives of this proposal are to assess and design borehole-based repositories in two rock formations deep beneath the Canadian prairies; i.e., a thick halite formation and a dense crystalline rock formation. This research program will help us achieve safe, low-emissions energy production, provide economic benefits for people and communities involved in mining and nuclear power, and support a flexible power generation option (SMRs) well-suited for remote Canadian communities. The research will also lead to uniquely trained, highly-qualified personnel experienced in the design of subsurface infrastructure for use in a variety of energy development and engineering applications.