Geoscientific arguments in support of the safety case for a deep geological repository in Southern Ontario, Canada

Abstract of the technical presentation presented at:
DAEF Conference, Cologne, Germany
September 26–28, 2016

Prepared by:
T.S. Nguyen, J. Brown and M. Herod
Canadian Nuclear Safety Commission

Z. Li
Independent geoenvironmental consultant

O. Nasir
Geofirma Engineering Ltd

Abstract:

Ontario Power Generation (OPG) has applied to the CNSC for a licence for site preparation and construction of a deep geological repository (DGR) for low- and intermediate-level waste in sedimentary rocks of Southern Ontario. In support of the licence application and the environmental assessment process, a long-term safety case was submitted to provide multiple lines of evidence that the environment and humans would be protected for very long periods of time after the DGR is sealed and closed.

CNSC staff have reviewed the long-term safety case by benchmarking it against international standards and best practices, performing independent calculations, conducting independent scientific research and seeking external advice on key safety aspects.

This presentation focuses on geoscientific aspects. From independent scientific research, review and calculations, CNSC staff have found multiple lines of evidence to support the conclusion that the host and cap rock formations for the proposed DGR would provide robust multiple barriers for the protection of the surface environment, including the Great Lakes:

• The deep groundwater system in the host and cap rock formations is hundreds of millions of years old and virtually stagnant, and isolated from the shallow groundwater and surface water.
• Those rock formations and their groundwater were unaffected by nine cycles of glaciation during the last million years.
• The Great Lakes are features resulting from quaternary glaciation cycles – surface water bodies such as the Great Lakes have remained isolated from the deep groundwater.
• Any potential radionuclide release from the DGR would be contained in the deep rock formations and would not reach shallow groundwater or surface water bodies such as the Great Lakes, even under extreme geological events, such as a future glaciation.

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