Radionuclide transport during glacial cycles: Comparison of two approaches for representing flow transients |
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| Institution: | 1. School of Geography and Earth Sciences, McMaster University, Hamilton, Ontario, Canada;2. Water Science and Technology Directorate, Environment and Climate Change Canada, Burlington, Ontario, Canada;1. Institute of Geosciences, Friedrich Schiller University Jena, Burgweg 11, 07749 Jena, Germany;2. Department Computational Hydrosystems, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany;3. Mathematics Department, Friedrich-Alexander University of Erlangen-Nuremberg, Cauerstraße 11, 91058 Erlangen, Germany;4. Tiberiu Popoviciu Institute of Numerical Analysis, Romanian Academy, Fantanele 57, 400320 Cluj-Napoca, Romania |
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| Abstract: | The effect of future, transient ice sheet movement and permafrost development on transport of radionuclides from a proposed repository site is investigated using numerical groundwater flow and radionuclide transport modelling. Two different transport approaches are compared, both utilizing groundwater flow simulations of future climate conditions. The first transport approach uses steady-state particle trajectories representing temperate climate conditions, but modifies the transport velocity along the trajectories according to the changing climate. The second approach is pseudo-transient by performing particle tracking in each individual flow field representing a given time epoch.Two different climate sequences are analyzed. First, a simplified sequence is assessed in order to understand if the two different transport approaches yield significantly different breakthrough characteristics. Second, a sequence representing conditions relevant for real safety assessment applications is considered.Results indicate that the transport approach using fixed trajectories tends to significantly over predict breakthrough during permafrost conditions relative to the pseudo-transient approach. The major difference between the two approaches is related to discharge locations. The fixed trajectory approach yields discharge locations constant in time whereas the pseudo-transient approach is characterized by discharge centres moving in time according to the different climate conditions. |
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