HR: 15:30h
AN: IA33A-07    [Abstracts]
TI: Regional and Site-Scale Hydrogeologic Analyses of a Proposed Canadian Deep Geologic Repository for Low and Intermediate Level Radioactive Waste
AU: * Sykes, J F
EM: sykesj@uwaterloo.ca
AF: University of Waterloo, Dept. of Civil and Environmental Engineering 200 Univesity Ave. W., Waterloo, ON N2L 3G1, Canada
AU: Normani, S D
EM: sdnorman@uwaterloo.ca
AF: University of Waterloo, Dept. of Civil and Environmental Engineering 200 Univesity Ave. W., Waterloo, ON N2L 3G1, Canada
AU: Yin, Y
EM: y2yin@engmail.uwaterloo.ca
AF: University of Waterloo, Dept. of Civil and Environmental Engineering 200 Univesity Ave. W., Waterloo, ON N2L 3G1, Canada
AU: Sykes, E A
EM: esykes@nwmo.ca
AF: Nuclear Waste Management Organization, 22 St. Clair Ave. E, Toronto, ON M4T 2S3, Canada
AB: A Deep Geologic Repository (DGR) for Low and Intermediate Level radioactive waste has been proposed by Ontario Power Generation for the eastern edge of the Michigan Basin at the Bruce site, near Tiverton, Ontario, Canada. The DGR is to be constructed within the argillaceous Ordovician limestone of the Cobourg Formation at a depth of about 680 m below ground surface. This paper describes a regional-scale and linked site-scale geologic conceptual model for the DGR site and analyzes flow system evolution using the FRAC3DVS-OPG flow and transport model. The work illustrates the factors that influence the predicted long-term performance of the geosphere barrier and provides a framework for the assembly and integration of site-specific geoscientific data. The structural contours at the regional and site scale of the 31 sedimentary strata that may be present above the Precambrian crystalline basement rock were defined by the Ontario Petroleum Institute's Oil, Gas and Salt Resources Library borehole logs covering Southern Ontario and by site-specific data. The regional- scale domain encompasses an 18,500 km2 region extending from Lake Huron to Georgian Bay. The site- scale spatial domain encompasses an area of approximately 361 km2 with the repository at its centre. Its boundary conditions are determined using both the nested model approach and an embedment approach. The groundwater zone below the Devonian is characterized by units containing pore fluids with high concentrations of total dissolved solids that can exceed 300 g/l. Site-specific data indicate that the Ordovician is under-pressured relative to the surface elevation while the Cambrian is over-pressured. The computational sequence for the analyses involves the calculation of steady-state density independent flow that is used as the initial condition for the determination of pseudo-equilibrium for a density-dependent flow system that has an initial TDS distribution developed from observed data. Sensitivity analyses can be computationally intensive, particularly for large-scale dynamic problems that couple energy, flow and mass transport. Important in the sensitivity analysis is the selection of the performance measure used to evaluate the system. The traditional metric of average water particle travel time is inappropriate for geologic units such as the Ordovician and lower Silurian where solute transport is diffusion dominant. The use of life expectancy and groundwater age is a more appropriate metric for such a system. The mean life expectancy for the DGR and base-case parameters has been estimated to be in excess of 8 million years. The analyses support the conclusion that solute transport in the Ordovician sediments is diffusion dominant.
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1847 Modeling
SC: International Association of Hydrogeologists, Canadian National Chapter [IA]
MN: 2009 Joint Assembly