Transport modelling of corrosive agents through a variably saturated bentonite buffer

Scott Briggs, Kenneth Birch, Magdalena Krol

Dans les comptes rendus d’articles de la conférence: GeoOttawa 2017: 70th Canadian Geotechnical Conference; 12th joint with IAH-CNC

Session: Radioactive Waste

ABSTRACT: for the long-term storage of used nuclear fuel. It is expected that a DGR will be located roughly 500 m below ground surface in crystalline or sedimentary rock. The DGR is designed with multiple engineered barriers including a steel container for the storage of used nuclear fuel, a copper coating for corrosion protection and a bentonite buffer to minimize groundwater transport in and out of the repository. Once placed in the repository, the saturation of the bentonite buffer will change due to the groundwater conditions in the repository and the heat coming from the used fuel. Over time, however, it is expected that the buffer will be fully saturated, operating as a transport barrier for corrosion agents moving towards the used fuel container. For example, sulphide, which can corrode copper and may be present in the surrounding pore water, could be transported into the placement room. The transport of sulphide under saturated conditions is well understood, however uncertainty remains regarding the transport of sulphide under the varying hydrogeologic conditions. In this study, equation was used to model the bentonite buffer saturation within the placement room assuming isothermal conditions and the results are compared with previous work that assumed a water saturated repository. Initial water saturation of the used fuel container occurred at 3,500 years while complete saturation of the placement room took 50,000 years.

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