Proposed Deep Geologic Repository for Low- and Intermediate-Level Radioactive Waste at the Bruce Nuclear Site

Abstract

This paper describes the current concept for Ontario Power Generation's proposed Deep Geologic Repository (DGR) to be located on the 900 ha Bruce Nuclear site. The Bruce Nuclear site is located approximately 225 kilometres northwest of Toronto. The underground repository concept is comprised of horizontally-excavated emplacement rooms arranged in parallel rows with access provided via two vertical concrete-lined shafts. The emplacement rooms would be constructed at a depth of about 660 m within limestone. This limestone formation is laterally extensive and is directly overlain by 200 m of low permeability shale. The low-permeability diffusion-controlled geosphere immediately surrounding the repository will assure long-term isolation of the low and intermediate-level radioactive waste (L&ILW). L&ILW will be retrieved from various storage structures at the WWMF and transferred to the DGR. L&ILW will also be shipped directly from the nuclear generating stations to the DGR. In this concept, most waste packages are retrieved and transferred 'as is' with shielding added, as necessary, to protect workers. The waste packages are lowered by hoist to the repository horizon and then transferred by forklift or, in the case of heavy packages, by train to emplacement rooms. Waste packages are stacked within emplacement rooms by forklift and, when full, the rooms are isolated by interim seals. It is expected that the repository will be open for at least 50 years to receive L&ILW from the operation and decommissioning of Ontario's nuclear reactors. When filled with waste and after receipt of all necessary regulatory approvals, the repository will be sealed by placing low permeability clay-based plugs in each shaft. A preliminary safety assessment indicates that predicted peak radiological impacts of the sealed repository will be many orders of magnitude below regulatory criteria.