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Assessing the Potential of Deep Borehole Disposal for Intermediate-level Nuclear Waste Management in Western Canada - DeepSAFE Paper presented at the International Conference on Energy Geotechnics, 17-20 June 2025, Paris FranceT10-Q04 University of Alberta Publication 2025-06-20 T10-Q04 Developing Advanced Criteria for Deep Borehole Disposal of Intermediate-level Waste from Nuclear Reactors by Identifying Regional Seals in the Western Canadian Sedimentary Basin through Carbon Isotopic Fingerprinting of Hydrocarbons T10-Q04 University of Alberta Publication 2025-05-12 T10-Q04 DeepSAFE – Feasibility of deep borehole disposal for SMR waste in Canada: Coupled THM modeling of ILW in WCSB. T10-Q04 University of Alberta Publication 2026-03-09 T10-Q04 Novel Geochemical Tool for Identifying Natural Geologic Seals for Deep Borehole Disposal: Mud Logging of Hydrocarbon Gas Isotopic Composition T10-Q04 University of Alberta Publication 2026-03-10 T10-Q04 UNLOCKING SUBSURFACE DISPOSAL OF INTERMEDIATE LEVEL RADIOACTIVE WASTE: CARBON ISOTOPIC FINGERPRINTING OF HYDROCARBON GASES AS A KEY NOVEL CRITERION FOR DEEP BOREHOLE DISPOSAL SITING IN THE WESTERN CANADA SEDIMENTARY BASIN Safe disposal of radioactive waste is essential for sustainable nuclear energy development in Canada and worldwide. As nuclear energy, application expands — particularly through the anticipated deployment of small modular reactors (SMRs) in Western Canada — there is growing interest to develop regionally adaptable, scientifically robust waste management strategies. Deep borehole disposal (DBD) emerged as a technically compelling approach for the long-term isolation of intermediate-level waste (ILW), relying on the passive integrity of deep geological formations rather than surface engineering alone [1, 2, 3].
DBD involves emplacing radioactive waste in narrow boreholes, typically 0.25 to 0.9 m in diameter, drilled to depths between 1.5 and 5 km within geologically stable formations [1, 2, 4] (Fig. 1a, b). The concept depends primarily on natural geological barriers — particularly low-permeability shale and siltstone units in the overlaying sedimentary basin — reinforced by engineered containment systems, to immobilize waste over geological timescales [5, 6, 7] (Fig. 1a, b). Its modularity, small surface footprint, and adaptability to local subsurface conditions make DBD particularly well suited to the decentralized deployment scenarios envisioned for SMRs in Alberta and Saskatchewan, provinces lacking existing nuclear infrastructure, but facing growing industrial energy demands [8].
Despite offering localized nuclear waste management solutions, a central challenge in DBD site selection remains the reliable demonstration of long-term geological containment. Existing site assessment frameworks have emphasized the use of inorganic geochemical proxies — notably dissolved inorganic and organic constituents of groundwater — as indicators of subsurface isolation [1, 5]. While valuable, these approaches provide limited direct insight into the processes governing fluid compartmentalization and barrier integrity. Gas-phase geochemical analyses in this context have largely targeted inorganic species, and the potential of organic gas isotope systematics remains substantially underexplored.
Here, we propose incorporating stable carbon isotopic fingerprinting of hydrocarbon gases, acquired through mud gas isotope logging (MGIL), as a key geochemical criterion for DBD siting and environmental assessment. MGIL continuously records the carbon isotopic composition (δ¹³C) of methane, ethane, propane, and butanes extracted from drilling muds during borehole advancement [9, 10, 11]. Isotopic depth profiles derived from MGIL resolve vertical heterogeneity in gas composition throughout the sedimentary column, and distinctive isotopic shifts at stratigraphic boundaries provide direct, geochemical process-based evidences of seal integrity and fluid compartmentalization [13].
The Western Canada Sedimentary Basin (WCSB) provides an ideal regional setting to develop and demonstrate this methodology. Its decades-long history of oil, gas, and geothermal development has produced a rich legacy of well data, including MGIL datasets that capture the isotopic signatures of natural seal formations across the basin. By repurposing this archive through the lens of DBD site assessment, we demonstrate that carbon isotopic fingerprinting of hydrocarbon gases can identify regionally effective seals, establish baseline geochemical conditions, and inform long-term monitoring strategies for prospective repositories. This study establishes MGIL as an innovative and transferable tool for DBD site characterization in the WCSB and beyond, advancing the scientific basis for secure, regionally adapted management of ILW.
T10-Q04 University of Alberta Publication 2026-06-14 T10-Q04
