| Assessing the Potential of Deep Borehole Disposal for Intermediate-level Nuclear Waste Management in Western Canada - DeepSAFEPaper presented at the International Conference on Energy Geotechnics, 17-20 June 2025, Paris France University of Alberta | Publication | 2025-06-20 | Shafaei Bajestani, M., Gabriela Gonzalez, Lopez Saavedra, S., Carlos Romano Perez, Zambrano Narvaez, G. |
| DeepSAFE – Feasibility of deep borehole disposal for SMR waste in Canada: Coupled THM modeling of ILW in WCSB. University of Alberta | Publication | 2026-03-09 | Shafaei Bajestani, M., Gabriela Gonzalez, Carlos Romano Perez |
| 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 University of Alberta | Publication | 2025-05-12 | Gabriela Gonzalez, Shafaei Bajestani, M., Lopez Saavedra, S., Zambrano Narvaez, G. |
| Novel Geochemical Tool for Identifying Natural Geologic Seals for Deep Borehole Disposal: Mud Logging of Hydrocarbon Gas Isotopic Composition University of Alberta | Publication | 2026-03-10 | Gabriela Gonzalez, Shafaei Bajestani, M., Carlos Romano Perez, Lopez Saavedra, S. |
| 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 BASINSafe 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.
University of Alberta | Publication | 2026-06-14 | Gabriela Gonzalez, "K. Muehlenbachs", Shafaei Bajestani, M., Lopez Saavedra, S., Zambrano Narvaez, G. |
| Investigating Potential (DeepSAFE) Deep borehole disposal solutions in Saskatchewan and Alberta for used ILW Fuel Emplacement from SMRs Invited speaker at the SRM summit 2025 as part of the Breakout Session: Building a robust nuclear ecosystem in Alberta - University of Alberta's key capacities for its sustainable development, present by UAlberta Researcher University of Alberta | Activity | 2025-03-04 | Zambrano Narvaez, G. |
| Numerical Validation of a Sequential Coupling between TOUGH3 and FLAC3D for Deep Borehole DisposalDeep borehole disposal is considered as a feasible disposal concept option for intermediate level-waste (ILW). Thermo-hydro-mechanical (THM) coupled processes govern geomechanical aspects for geological disposal. Therefore, understanding of these coupled processes is essential for accurately analyzing and predicting long-term performance of geological disposal systems. Numerical modeling can improve the understanding of such complex interaction among heat transfer, fluid flow, and mechanical responses in porous media. In addition, it can help define suitable conditions for geological disposal.
To conduct an adequate assessment of the performance and changes in the conditions of the disposal system after closure, as well as study the associated risks in the absence of engineered barriers, it is necessary to generate numerical model scenarios exploring the effectiveness of natural barriers at containing radionuclides (when all the engineered barriers have failed e.g., glass matrix, primary package, and overpack.)
However, to be able to carry out post-closure safety assessment based on numerical modeling it is necessary to implement a model that considers thermo-hydro-mechanical coupling. In this work a sequential coupling between TOUGH3 and FLAC3D is validated. University of Alberta | Activity | 2025-03-04 | Carlos Romano Perez, Zambrano Narvaez, G. |
| SMR 2025 Breakout Session C: Building a robust nuclear ecosystem in Alberta: U of A’s key capabilities for its sustainable development, presented by the University of Alberta University of Alberta | Activity | 2026-04-02 | Zambrano Narvaez, G. |
| SMR Forum 2024 University of Alberta | Activity | 2025-04-10 | Zambrano Narvaez, G. |
| SMR Forum 2025Participation at the 2025 SMR Forum University of Alberta | Activity | 2025-09-25 | Zambrano Narvaez, G. |
| SMR Summit 2024First oficial event post inauguration of this FES program. Very important networking and connections that leaded to successful expansion program of this research topic. University of Alberta | Activity | 2025-04-03 | Zambrano Narvaez, G. |
