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Reactive Transport Processes in Compacted Bentonite

A.E. Idiart1 M. Pekala1 A. Nardi1 D. Arcos1
1Amphos 21, Barcelona, Spain

Time evolution of Ca unit fraction on the cation exchanger. The time increases from left (initial state) to right (final state – after 880 days).

The Swedish Organization for Radioactive Waste (SKB) is considering disposal High Level Wastes in a deep underground repository. Bentonite clay is planned to be used in the near-field of the waste packages as buffer material. The buffer is expected to provide a favorable environment with limited radionuclide migration due to slow diffusion and retardation by sorption and cation-exchange effects. A modeling of these bentonites has been undertaken to verify whether a reactive transport model with cation-exchange can explain the observed experimental patterns. This work has implemented a reactive transport model using the Subsurface Flow Module and a set of DAE. The obtained results agree well with experimental data and provide insight into the processes behind solute transport in bentonite.

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