Ontario Power Generation's Proposed L&ILW Deep Geologic Repository: Geoscientific Assessment

Abstract

The Nuclear Waste Management Organization (NWMO) recently completed geoscientific studies on behalf of Ontario Power Generation (OPG) to verify the suitability of the Bruce nuclear site, Municipality of Kincardine, Ontario, to host a Deep Geologic Repository (DGR) for OPG’s Low and Intermediate Level Nuclear Waste (L&ILW). The Bruce nuclear site is underlain by a ≈850 m thick Paleozoic sedimentary sequence comprised of near-horizontally layered Cambrian- to Devonian-age sediments occurring on the eastern flank of the Michigan Basin. As envisioned, the proposed DGR would be excavated at a depth of ≈680 m within the upper Ordovician argillaceous limestone Cobourg Formation. Multi-phase geoscientific studies conducted over 4-years indicate that the upper Ordovician formations proposed to host and enclose the DGR comprise a laterally traceable, stable, saline (TDS ≈200-350 g/L) and low permeability (≤10^-13 m/s) groundwater regime in which solute migration has been dominated by diffusive processes. This paper provides an overview of the coordinated site-specific and regional geoscientific studies and how they have provided a basis to understand both the current site conditions and, past and future site evolution as it relates to the assessment of long-term passive DGR safety.