The Dissolution and Transport of Radionuclides From Used Nuclear Fuel in an Underground Repository

Y. Beauregard[1], M. Gobian[2], and F. Garisto[2]
[1]University of Western Ontario, London, ON, Canada
[2]Nuclear Waste Management Organization, Toronto, ON, Canada

In the Canadian concept for a deep geological repository for used nuclear fuel, the used fuel bundles are placed in containers consisting of an inner steel vessel surrounded by a copper shell. The filled containers are placed in excavated tunnels or boreholes and surrounded by a compacted bentonite clay buffer material. In the event of container failure, the rate of migration of radionuclides to the surface biosphere is limited by the rate of nuclide release from the fuel matrix and by nuclide transport through multiple engineered and geological barriers.

The purpose of this work was to gain experience with COMSOL Multiphysics as a potential tool for safety assessment modelling as well as to generate information for comparison with another more simplified safety assessment tool. The Earth Science Module was used to model the dissolution of the used fuel matrix as a function of alpha, beta and gamma dose rates and to then study the release of radionuclides from a pin-hole defect in the container wall.