Gaining insight into corrosion processes from numerical simulations of an integrated iron-claystone experiment
Olivier Bildstein, Jean-Éric Lartigue, Michel L. Schlegel, Christian Bataillon, Benoît Cochepin, Isabelle Munier, Nicolas Michau, 2017. "Gaining insight into corrosion processes from numerical simulations of an integrated iron-claystone experiment", Radioactive Waste Confinement: Clays in Natural and Engineered Barriers, S. Norris, J. Bruno, M. van Geet, E. Verhoef
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Numerical simulations concerning iron–clay interactions in the conditions of an integrated experiment were conducted within a Callovo-Oxfordian claystone block at 90°C for 2 years. The calculations aim at determining the configurations and the parameters for which the simulation reproduce the mineral paragenesis observed at the end of the experiment. This paragenesis suggests that a thin magnetite layer precipitates at the surface of the corroding iron and dissolves on the claystone side to promote precipitation of Fe-silicate and Fe-carbonate minerals. The claystone is also altered close to the interface with iron via a significant precipitation of a Fe-carbonate mineral.
The results obtained using the coupled reactive transport code Crunchflow show that adjusting both the kinetics of magnetite dissolution/precipitation and the properties of the corroded layer (considered as a diffusive barrier) was required in order: (i) to model the destabilization of the magnetite layer formed at the original iron–claystone interface early in the corrosion process and the precipitation of other iron-bearing minerals; and (ii) to isolate the chemical conditions at the iron surface from the conditions in the clay environment in order to favour magnetite precipitation at the iron surface. With these assumptions, the model closely reproduced the mineral paragenesis observed in the experiment.
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It is internationally accepted that the safest and most sustainable option for managing radioactive waste is geological disposal, utilizing both engineering and geology to isolate the waste and contain the radioactivity.
This Special Publication contains 25 scientific studies presented at the 6th conference on ‘Clays in natural and engineered barriers for radioactive waste confinement’ held in Brussels, Belgium in 2015. The conference and this resulting volume cover many of the aspects of clay characterization and behaviour considered at various temporal and spatial scales relevant to the confinement of radionuclides in clay, from basic phenomenological process descriptions to the global understanding of performance and safety at repository and geological scales.
The papers in this volume consider research into argillaceous media under the following topic areas: large-scale geological characterization; general strategy for clay-based disposal systems; geomechanics; mass transfer; bentonite evolution and gas transfer.
The collection of different topics presented in this Special Publication demonstrates the diversity of geological repository research.