Hostname: page-component-78c5997874-v9fdk Total loading time: 0 Render date: 2024-11-10T07:11:35.802Z Has data issue: false hasContentIssue false
  • English
  • Français

A mechanism for bentonite buffer erosion in a fracture with a naturally varying aperture

Published online by Cambridge University Press:  02 January 2018

Christopher Reid ,
Rebecca Lunn ,
Gráinne El Mountassir  and
Alessandro Tarantino
Christopher Reid*
Affiliation:
Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow G1 1XQ, UK
Rebecca Lunn
Affiliation:
Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow G1 1XQ, UK
Gráinne El Mountassir
Affiliation:
Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow G1 1XQ, UK
Alessandro Tarantino
Affiliation:
Department of Civil and Environmental Engineering, University of Strathclyde, Glasgow G1 1XQ, UK
*
*E-mail: christopher.reid@strath.ac.uk
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

In the deep geological disposal of nuclear waste in crystalline rock, erosion of the bentonite buffer may occur during periods of glaciation. Previous researchers have examined the mechanism and rates of extrusion and erosion for purified montmorillonite samples in smooth planar fractures. In this paper, we investigate the influence of using MX-80 material (as delivered, i.e. including accessory minerals) and a naturally varying aperture on bentonite erosion. A bespoke fracture flow cell was constructed for this purpose and flow through conducted with deionized water. Throughout the experiment, gravimetric analysis was undertaken on the effluent and the swelling pressure of the bentonite monitored. Quantitative image analysis of the extrusion process was also undertaken. When the swelling pressure data were analysed, alongside both the oscillations in erosion rate and the area of the accessory-mineral ring, a two-stage mechanism governing the erosion process became apparent. Once an accessory-mineral ring had formed at the edge of the extruded material, further increases in swelling pressure resulted in a breach in the accessory-mineral ring, triggering an erosive period during which, the mineral ring was supplemented with additional minerals. The cycle repeated until the ring was sufficiently strong that it remained intact. This observed process results in erosion rates one order of magnitude less than those currently used in long-term safetycase calculations.

Keywords

bentonitemontmorillonitebuffererosionnuclear-waste disposal
Type
Research Article
Information
Mineralogical Magazine , Volume 79 , Issue 6 , November 2015 , pp. 1485 - 1494
Creative Commons
Creative Common License - CCCreative Common License - BY
Copyright © The Mineralogical Society of Great Britain and Ireland 2015. This is an open access article, distributed under the terms of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2015

References

Apted, MI, Arthur, R., Bennett, D., Savage, D., Sällfors, G. and Wennerström, H. (2010) Buffer erosion - An overview of concepts and potential safety consequences. SSM report 2010-31.Google Scholar
Cui, Y and Tang, A.M. (2013) On the chemo-thermo-hydro-mechanical behaviour of geological and engineered barriers. Journal of Rock Mechanics and Geotechnical Engineering, 5, 169–178.CrossRefGoogle Scholar
Juvankoski, M., Ikonen, K., and Jalonen, T. (2012) Buffer production line 2012: Design, production and initial state of the buffer. Posiva report 2012-17.Google Scholar
Kiviranta, L. and Kumpulainen, S. (2011) Quality control and characterisation of bentonite materials. Posiva work report 2011-84.Google Scholar
Neretnieks, I., Moreno, L. and Liu, L. (2009) Mechanisms and models for bentonite erosion. SKB Technical Report TR-09-35, Swedish Nuclear Fuel and Waste Management Co., Stockholm.Google Scholar
Richards, T. (2010) Particle Clogging in Porous Media — Filtration of a Smectite Solution. SKB Technical Report TR-10-22, Swedish Nuclear Fuel and Waste Management Co., Stockholm.Google Scholar
Richards, T. and Neretnieks, I. (2010) Filtering of clay colloids in bentonite detritus material. Chemical Engineering Technology, 33, 1303–1310.CrossRefGoogle Scholar
Schatz, T., Kanerva, N., Martikainen, J., and Sane, P. (2013) Buffer erosion in dilute groundwater. Posiva report 2012-44.Google Scholar
SKB (2010) Design, production and initial state of the buffer. SKB Technical Report TR-10-15, Swedish Nuclear Fuel and Waste Management Co., Stockholm.Google Scholar
SKB (2011) Long-term safety for the final repository for spent nuclear fuel at Forsmark. Main report of the SR-Site project. Updated 2012-12. Technical Report TR-11-01.Google Scholar
Vilks, P. and Miller, N.H. (2010) Laboratory bentonite erosion experiments in a synthetic and a natural fracture. NWMO Technical Report TR-2010-16.Google Scholar
Witherspoon, P.A., Wang, J.S.Y., Iwail, K. and Gale, J.E. (1979) Validity of cubic law for fluid flow in a deformable rock fracture. Water Resources Research.Google Scholar