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Assessing the Long-Term Behaviour of the Industrial Bentonites Employed in a Repository for Radioactive Wastes by Studying Natural Bentonites in the Field

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Bedrock Geosciences, Veltheimerstrasse 18, 5105 Auenstein, Switzerland
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Geological Survey of Finland (GTK), P.O. Box 96, 02151 Espoo, Finland
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Previous Address Saanio & Riekkoloa, Laulukuja 4, 00420 Helsinki, Finland
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Scottish Universities Environmental Research Centre (SUERC), Rankine Avenue, East Kilbride G75 0QF, UK
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British Geological Survey (BGS), Nicker Hill, Keyworth NG12 5GG, UK
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Pitty (EIA) Consulting, Telegraph Lane East, Norwich NR1 4AN, UK
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Geoinvest, P.O. Box 20476, 2152 Aglantzia, Cyprus
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Author to whom correspondence should be addressed.
Academic Editors: Rebecca Lunn, Simon Harley, Simon Norris and Jesus Martinez-Frias
Geosciences 2017, 7(1), 5; https://doi.org/10.3390/geosciences7010005
Received: 26 September 2016 / Revised: 29 November 2016 / Accepted: 20 December 2016 / Published: 18 January 2017
Bentonite makes an important contribution to the performance of the engineered barriers in most radioactive waste repository designs. The choice of bentonite results from its favourable properties for waste isolation and its stability in relevant geological environments. However, the longevity of bentonite (especially the resistance to waste container sinking) has been little studied. Modelling results suggest significant bentonite deformation and associated canister sinking is unlikely and, here, long-term natural system data are used as a reality check on model predictions. Results indicate that bentonite from the investigated site shows no significant deviation in bulk physical parameters from repository bentonite. However, micro-scale shear planes can be seen throughout the sampled cores. The presence of multi-directional S- and C-type shears suggests they originate from loading from the overlying limestone, not gravitational tectonics. The plastic limits and angles of shearing resistance for natural and repository bentonites suggest both are susceptible to shearing. The impact of bentonite shear under load could be minimised by appropriate design, but existing lower activity waste container designs do not consider the potentially high external stresses from the bentonite backfill and this should be addressed in future. View Full-Text
Keywords: bentonite; waste canister sinking; shear displacement; reality check; engineering options bentonite; waste canister sinking; shear displacement; reality check; engineering options
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Alexander, W.R.; Reijonen, H.M.; MacKinnon, G.; Milodowski, A.E.; Pitty, A.F.; Siathas, A. Assessing the Long-Term Behaviour of the Industrial Bentonites Employed in a Repository for Radioactive Wastes by Studying Natural Bentonites in the Field. Geosciences 2017, 7, 5.

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