The Nuclear Waste Management Organization (NWMO) is responsible for the implementation of Adaptive Phased Management, the federally-approved plan for the safe long-term management of Canada’s used nuclear fuel. Under this plan, used nuclear fuel will ultimately be placed within a deep geological repository in a suitable host rock formation.

The NWMO recently completed a study illustrating the postclosure safety of a hypothetical used fuel repository in a crystalline host formation. The Base Case scenario assumes that undetected defects in used fuel containers lead to the release of radionuclides to the geosphere. The primary pathway to the biosphere is through a water supply well. To be conservative, the scenario assumes that the well and the defective containers are located such that radionuclide transport to the well is maximized.

In a complex faulted flow system, the most consequential locations for used fuel container failures and the water supply well are not obvious. This paper presents a robust approach to identifying the most consequential well-source location pairs. The approach relies on a mixture of numerical methods and the availability of cluster-computing capabilities. A refined “brute-force” approach simulates total repository failure with complete but coarse spatial coverage of all possible well locations. Spatially segregated groups of possible high-consequence well locations are extracted and associated potential high-consequence container failure locations determined. Well and container locations are refined and permutations evaluated until maximum well transport is determined within the resolution of the numeric grid.