Hostname: page-component-78c5997874-dh8gc Total loading time: 0 Render date: 2024-11-10T11:44:33.287Z Has data issue: false hasContentIssue false
  • English
  • Français

Avoiding unrealistic behaviour in coupled reactive-transport simulations of cation exchange and mineral kinetics in clays

Published online by Cambridge University Press:  14 February 2019

Steven Benbow ,
James Wilson ,
Richard Metcalfe  and
Jarmo Lehikoinen
Steven Benbow*
Affiliation:
Quintessa Limited, Videcom House, Newtown Road, Henley-on-Thames, UK
James Wilson
Affiliation:
Quintessa Limited, Videcom House, Newtown Road, Henley-on-Thames, UK
Richard Metcalfe
Affiliation:
Quintessa Limited, Videcom House, Newtown Road, Henley-on-Thames, UK
Jarmo Lehikoinen
Affiliation:
STUK – Radiation and Nuclear Safety Authority, Helsinki, Finland
*
*E-mail: stevenbenbow@quintessa.org
Get access Rights & Permissions [Opens in a new window]

Abstract

Bentonite clay is often included as a buffer, backfill and/or sealing material in designs for deep geological repositories for radioactive wastes. It is expected that bentonite materials may undergo some mineralogical alteration as they interact with in situ groundwaters over long timescales on the order of thousands to millions of years. Long-term modelling of these materials is therefore important in order to demonstrate confidence that the engineered designs will continue to perform as required over their intended lifetimes (required assessment timescales can be up to 1 million years). The key geochemical processes that must be considered in such modelling are mineral dissolution and precipitation and cation exchange. These processes are expected to occur simultaneously and so modelling of their coupled effects and their rates (kinetics) is necessary. Illustrative reactive-transport models of the geochemical alteration of montmorillonite (the primary mineral in bentonite exhibiting cation exchange) are presented which demonstrate that one possible approach to fully coupling cation exchange and clay mineral dissolution kinetics, referred to here as the ‘all-component coupling’ approach, may lead to unrealistic behaviour due to feedback that may occur in the formulation. This feedback can be avoided if a ‘common-component’ conceptual model for the dissolution of exchanger end members is adopted, where only the saturation of the exchanger ‘structural unit’ is considered when evaluating the potential for dissolution of the mineral. Such considerations have been proposed historically in stability analyses for montmorillonite, but have not been explored widely in the modelling literature.

Keywords

reactive-transport modellingradioactive waste disposalcoupled modellingion exchangesmectite stability
Type
Article
Information
Clay Minerals , Volume 54 , Issue 1 , March 2019 , pp. 83 - 93
Copyright
Copyright © Mineralogical Society of Great Britain and Ireland 2019 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

Associate Editor: Chris Greenwell

References

Appelo, C.A.J. & Postma, D. (2005) Geochemistry, Groundwater and Pollution, 2nd edition. A. A. Balkema Publishers, Amsterdam, The Netherlands.Google Scholar
Bankole, O., El Albani, A., Meunier, A., Pambo, F., Paquette, J.-L. & Bekker, A. (2018) Earth's oldest preserved K-bentonites in the ca. 2.1 Ga Francevillian Basin, Gabon. American Journal of Science, 318, 409–434.Google Scholar
Bethke, C.M. (2008) Geochemical and Biogeochemical Reaction Modelling. Cambridge University Press, Cambridge, UK.Google Scholar
Bildstein, O., Trotignon, L., Perronnet, M. & Jullien, M. (2006) Modelling iron–clay interactions in deep geological disposal. Physics and Chemistry of the Earth, 31, 618–625.Google Scholar
Fujii, N., Yamakawa, M., Shikazono, N. & Sato, T. (2015) Geochemical and mineralogical characterisation of bentonite interacted with alkaline fluids generating in Zambales Ophiolite, northwestern Luzon, Philippines. Journal of the Geological Society of Japan, 120, 361–375 (in Japanese with English abstract).Google Scholar
Gaucher, E.C., Blanc, P., Matray, J.-M. & Michau, N. (2004) Modeling diffusion of an alkaline plume on a clay barrier. Applied Geochemistry 19, 1505–1515.Google Scholar
Helgeson, H.C., Delany, J.M., Nesbitt, H.W. & Bird, D.K. (1978) Summary and critique of the thermodynamic properties of rock-forming minerals, American Journal of Science, 278A, 204–220.Google Scholar
Johnson, J.W., Oelkers, E.H. & Helgeson, H. (1992) SUPCRT92: a software package for calculating the standard molal thermodynamic properties of minerals, gases, aqueous species, and reactions for 1–5000 bar and 0–1000°C. Computers & Geosciences, 18, 899–947.Google Scholar
Karnland, O. & Birgersson, M. (2006) Montmorillonite Stability with Respect to KBS-3 Conditions. SKB Technical Report TR-06-11. Swedish Nuclear Fuel and Waste Management Company, Stockholm, Sweden.Google Scholar
Kittrick, J.A. (1971) Stability of montmorillonites: I. Belle Fourche and clay spur Montmorillonites. Soil Science Society of America Proceedings, 35, 140–145.Google Scholar
Madsen, F.T. (1998) Clay mineralogical investigations related to nuclear waste disposal. Clay Minerals, 33, 109–129.Google Scholar
Marty, N., Fritz, B., Clément, A. & Michau, N. (2010) Modelling the long term alteration of the engineered bentonite barrier in an underground radioactive waste repository. Applied Clay Science, 47, 82–90.Google Scholar
Quintessa (2013) QPAC: Quintessa's General-Purpose Modelling Code. Quintessa Report QRS-QPAC-11. Quintessa Ltd, Henley-on-Thames, UK. Available at: www.quintessa.org/qpac-overview-report.pdf.Google Scholar
Reijonen, H.M. & Alexander, W.R. (2015) Bentonite analogue research related to geological disposal of radioactive waste: current status and future outlook. Swiss Journal of Geosciences, 108, 101–110.Google Scholar
Samper, J., Lu, C. & Montenegro, L. (2008) Reactive transport model of interactions of corrosion products and bentonite. Physics and Chemistry of the Earth, 33, S306–S316.Google Scholar
Samper, J., Naves, A., Montenegro, L. & Mon, A. (2016) Reactive transport modelling of the long-term interactions of corrosion products and compacted bentonite in a HLW repository in granite: uncertainties and relevance for performance assessment. Applied Goechemistry, 67. 42–51.Google Scholar
Savage, D., Noy, D., & Mihara, M. (2002) Modelling the interaction of bentonite with hyperalkaline fluids. Applied Geochemistry, 17, 207–223.Google Scholar
Savage, D., Walker, C., Arthur, A., Rochelle, C., Oda, C. & Takase, H. (2007) Alteration of bentonite by hyperalkaline fluids: a review of the role of secondary minerals. Physics and Chemistry of the Earth, 32, 287–297.Google Scholar
Savage, D., Benbow, S., Watson, C., Takase, H., Ono, K., Oda, C. & Honda, A. (2010a) Natural systems evidence for the alteration of clay under alkaline conditions: an example from Searles Lake, California. Applied Clay Science, 47, 72–81.Google Scholar
Savage, D., Arthur, R., Watson, C. & Wilson, J. (2010b) An Evaluation of Models of Bentonite Porewater Evolution. SSM Technical Report 2010-12. Swedish Radiation Safety Authority, Stockholm, Sweden.Google Scholar
Savage, D., Watson, C., Benbow, S. & Wilson, J. (2010c) Modelling iron–bentonite interactions. Applied Clay Science, 47, 91–98.Google Scholar
Steefel, C. (2008) Geochemical kinetics and transport. Pp. 545–589 in Kinetics of Water–Rock Interaction (Brantley, S.L., Kubicki, J.D. & White, A.F., editors). Springer, New York, NY, USA.Google Scholar
Vulava, V.M., Kretschmar, R. & Rusch, U. (2000) Cation competition in a natural subsurface material: modeling of sorption equilibria. Environmental Science and Technology, 34, 2149–2155.Google Scholar
Watson, C., Benbow, S. & Savage, D. (2007) Modelling the Interaction of Low pH Cements and Bentonite. Issues Affecting the Geochemical Evolution of Repositories for Radioactive Waste. SKI Report 2007:30. Swedish Nuclear Power Inspectorate, Stockholm, Sweden.Google Scholar
Wilson, J.C., Benbow, S., Watson, C., Sasamoto, H. & Savage, D. (2015) Fully-coupled reactive transport models of the iron–bentonite interface. Applied Geochemistry, 61, 10–28.Google Scholar
Wilson, J., Benbow, S., Metcalfe, R. & Leung, H. (2017) Reactive transport modelling of shale–bentonite interactions in a hypersaline environment. Applied Geochemistry, 76, 60–73.Google Scholar
Wilson, J., Savage, D., Bond, A., Watson, S., Pusch, R. & Bennett, D. (2011) Bentonite: A Review of Key Properties, Processes and Issues for Consideration in the UK Context. Quintessa Report QRS-1378ZG Version 1.1 for Radioactive Waste Management Directorate. Nuclear Decommissioning Authority, Harwell, UK.Google Scholar
Yamaguchi, T., Sakamoto, Y., Akai, M., Takazawa, M., Iida, Y., Tanaka, T. & Nakayama, S. (2007) Experimental and modeling study on long-term alteration of compacted bentonite with alkaline groundwater. Physics and Chemistry of the Earth, 32, 298–310.Google Scholar