Integrated molecular profiling to explore the microbiology of deep geological repository components for storage of used nuclear fuel

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Established in 2002 by the Nuclear Fuel Waste Act, the Nuclear Waste Management Organization (NWMO) is responsible for the long-term management of all of Canada's used nuclear fuel. In accordance with international scientific consensus, this requires the construction of a deep geological repository (DGR) that employs a multi-barrier system. The proposed DGR will be constructed ~500 m below ground in a stable low-permeability host rock and will seal used fuel inside copper-coated carbon steel used fuel containers (UFCs) where carbon steel provides strength and copper confers corrosion protection. The UFCs will be placed within highly compacted bentonite (HCB) boxes and stored in underground emplacement rooms. Bentonite is a low permeability clay that swells when saturated with groundwater, making it an excellent sealing material. For long-term stability, it will be critical for both the engineered and natural barrier components of a DGR to minimize microbial growth and activity over geological timeframes. This NSERC Alliance proposal will involve coordinated sampling and analysis efforts to generate new insight into the microbiology of components of a DGR, possible host sites, and naturally occurring geological analogues for such systems. The proposed research will use cutting-edge microbiology and biogeochemical analytical techniques to explore microbial profiles and associated natural organic matter (NOM) profiles from subsurface rock and groundwater samples, which is an important step toward building a safety case for a potential DGR site. Experimental work with bentonite clay that is intended for use within the engineered barrier components will help identify signatures of microbial viability and persistence under the expected conditions. Microbial and NOM profiles from naturally occurring rock and water samples associated with geological repository analogue systems will also be studied to better predict the stability and activity of microorganisms. Overall, the research and deliverables proposed here will be essential for building a safety case that help with confident design and implementation of a DGR for permanent storage of Canada's high-level nuclear waste.