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In-situ experiments on bentonite-based buffer and sealing materials at the Mont Terri rock laboratory (Switzerland)

  • Klaus Wieczorek
  • Irina Gaus
  • Juan Carlos Mayor
  • Kristof Schuster
  • José-Luis García-Siñeriz
  • Toshihiro Sakaki
Chapter
Part of the Swiss Journal of Geosciences Supplement book series (SWISSGEO, volume 5)

Abstract

Repository concepts in clay or crystalline rock involve bentonite-based buffer or seal systems to provide containment of the waste and limit advective flow. A thorough understanding of buffer and seal evolution is required to make sure the safety functions are fulfilled in the short and long term. Experiments at the real or near-real scale taking into account the interaction with the host rock help to make sure the safety-relevant processes are identified and understood and to show that laboratory-scale findings can be extrapolated to repository scale. Three large-scale experiments on buffer and seal properties performed in recent years at the Mont Terri rock laboratory are presented in this paper: The 1:2 scale HE-E heater experiment which is currently in operation, and the full-scale engineered barrier experiment and the Borehole Seal experiment which have been completed successfully in 2014 and 2012, respectively. All experiments faced considerable difficulties during installation, operation, evaluation or dismantling that required significant effort to overcome. The in situ experiments show that buffer and seal elements can be constructed meeting the expectations raised through small-scale testing. It was, however, also shown that interaction with the host rock caused additional effects in the buffer or seal that could not always be quantified or even anticipated from the experience of small-scale tests (such as re-saturation by pore-water from the rock, interaction with the excavation damaged zone in terms of preferential flow or mechanical effects). This led to the conclusion that testing of the integral system buffer/rock or seal/rock is needed.

Keywords

Engineered barrier system In-situ experiments Bentonite Sand–bentonite mixture Nuclear waste disposal 

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Notes

Acknowledgements

Research leading to the results presented here has received funding from the European Atomic Energy Community’s fifth Framework Programme (1998–2002) under contract FIKW-CT-2000-00017, from the European Atomic Energy Community’s Sixth Framework Programme (2002–2006) under contract FI6 W-CT-2004-07-20-508851, from the European Atomic Energy Community’s Seventh Framework Programme (2007–2011) under grant agreement No. 249681, from the German Federal Ministry of Economics and Energy, and from the Swiss Federal Office for Education and Science. This paper has been reviewed by Michael Jobmann, DBE Technology GmbH, Peine, Germany, and by Dr. Elie Valcke, SCK.CEN, Mol, Belgium.

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Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) gGmbHBraunschweigGermany
  2. 2.Nationale Genossenschaft fuer die Lagerung radioaktiver Abfälle (Nagra)WettingenSwitzerland
  3. 3.Empresa Nacional de Residuos Radiactivos, S.A. (ENRESA)MadridSpain
  4. 4.Bundesanstalt fuer Geowissenschaften und Rohstoffe (BGR)HannoverGermany
  5. 5.Amberg InfrastructurasAlcobendasSpain

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