Determining the Most Consequential Well and Source Locations for Postclosure Safety Assessment of a Conceptual Deep Geological Repository in Crystalline Rock

The Nuclear Waste Management Organization (NWMO) is responsible for the safe and secure long-term management of used nuclear fuel produced in Canada. Recently the NWMO conducted a postclosure safety assessment study for a conceptual deep geological repository (DGR) at a hypothetical crystalline rock site in the Canadian Shield. For safety assessment purposes, it is assumed that undetected defects in some used fuel containers lead to the release of radionuclides to the geosphere with the primary pathway to the biosphere being a deep water-supply well that is tapping water from a fracture zone. To be conservative, the well and the defective containers are assumed located such that radionuclide transport to the well is maximized. This study focuses on identifying the most consequential well-source location pairs using a systematic approach. Results demonstrate that the methodology developed is effective in identifying the most dose consequential well and source locations in a fractured geosphere. The methodology is not site-specific and can be applied to other fractured crystalline sites.