Hostname: page-component-8448b6f56d-jr42d Total loading time: 0 Render date: 2024-04-23T23:33:18.940Z Has data issue: false hasContentIssue false
  • English
  • Français

Cracking in a cementitious backfill and its implications for flow and chemistry

Published online by Cambridge University Press:  05 July 2018

B. T. Swift ,
P. B. Bamforth  and
G. M. N. Baston
B. T. Swift*
Affiliation:
AMEC, Building 150, Thomson Avenue, Harwell Oxford, Didcot, Oxfordshire OX11 0QB, UK
P. B. Bamforth
Affiliation:
8 Hamilton Court, Hamilton Road, Ealing, London W5 2EJ, UK
G. M. N. Baston
Affiliation:
AMEC, Building 150, Thomson Avenue, Harwell Oxford, Didcot, Oxfordshire OX11 0QB, UK
*
*E-mail: ben.swift@amec.com
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 UK, disposal of packaged intermediate-level radioactive waste may involve waste packages being placed in a geological disposal facility (GDF) and surrounded by a cementitious backfill. Cracking of the backfill could occur due to a number of mechanisms, and this could affect the post-closure performance of the GDF.

This work has assessed potential cracking in the backfill during the backfilling and early post-closure period of GDF vaults with an open crown space in a higher strength rock. From the comprehensive range of processes considered, three were identified as potentially causing cracking: (1) during backfilling, plastic settlement under solid horizontal surfaces could result in horizontal gaps beneath waste packages; (2) within days of backfilling, early-age thermal contraction of the backfill could result in primarily vertical cracks; (3) over a number of years, expansion of waste packages could result in large horizontal cracks.

A groundwater flow model incorporating a representation of the cracks was used to calculate flows through a backfilled GDF vault, and through the cracks themselves. Including cracks increased the flow rate significantly. A reactive transport model was used to estimate the evolution of the pore water chemistry as groundwater flows through the cracked backfill. Calcite and brucite were predicted to precipitate, with brucite subsequently dissolving. Calcite build-up could seal some cracks.

Keywords

wastegeological disposalcementitious backfillcrackinggroundwater flowpHbrucitecalcitearmouring
Type
Research Article
Information
Mineralogical Magazine , Volume 76 , Issue 8 , December 2012 , pp. 3071 - 3082
Creative Commons
Creative Common License - CCCreative Common License - BY
© [2012] The Mineralogical Society of Great Britain and Ireland. This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY) licence (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 2012

References

Baston, G.M.N., Heath, T.G. and Hunter, F.M.I. (2008) Summary of Additions and Amendments to Data in the HATCHES Chemical Thermodynamic Database 2002 to 2007. Serco Report SA/ENV-0934.Google Scholar
Baston, G., Glasser, F., Smith, V. and Hoch, A. (2011) Modelling pH Evolution in the Near-field of a Geological Disposal Facility for ILW/LLW. Serco Report SERCO/003011/003.Google Scholar
Benbow, S., Watson, C., Savage, D. (2005) Investigating Conceptual Models for Physical Property Couplings in Solid Solution Models of Cement. SKI Report 2005:64.Google Scholar
Bond, K.A. and Tweed, C.J. (1995) Groundwater Compositions for the Borrowdale Volcanics Group, Boreholes 2, 4 and RCF3, Sellafield, Evaluated using Thermodynamic Modelling. United Kingdom Nirex Ltd Report NSS/R397.Google Scholar
Brodersen, K. and Nilsson, K. (1992) Pores and cracks in cemented waste and concrete. Cement and Concrete Research, 22, 405–417.CrossRefGoogle Scholar
Chambers, A.V., Jackson, C.P., Wilding, C.R. and Swift, B.T. (2007) Data for a Representation of Physical Containment in a Repository-scale Model. Serco Report SA/ENV-0658, Issue 2.Google Scholar
Francis, A.J., Cather, R. and Crossland, I.G. (1997) Development of the Nirex Reference Vault Backfill: Report on Current Status in 1994. United Kingdom Nirex Ltd Science Report S/97/014.Google Scholar
Glasser, F.P., Marchand, J. and Samson, E. (2008) Durability of concrete - degradation phenomena involving detrimental chemical reactions. Cement and Concrete Research, 38, 226–246.CrossRefGoogle Scholar
Harris, A.W. and Nickerson, A.K. (1995) The Masstransport Properties of Cementitious Materials for Radioactive Waste Repository Construction. United Kingdom Nirex Ltd Report NSS/R309.Google Scholar
Hoch, A.R. (2008) ‘‘Screening limit’’ on the Rate of Gas Generation from Individual Waste Containers. Serco Report SA/ENV-0888, Issue 2.Google Scholar
Holland, T.R. and Tearle, W.M. (2003) A Review of NRVB Mineralogy. Serco Report SERCO/ERRA- 0455.Google Scholar
Nirex (1994) Dounreay Geological Investigations. Hydrogeology. United Kingdom Nirex Ltd Report No. 660.Google Scholar
Nirex (2007) Generic Repository Studies: Generic Waste Package Specification, Volume 1 - Specification. United Kingdom Nirex Ltd Report N/104 (Issue 2).Google Scholar
Nuclear Decommissioning Authority (2010a) Geological Disposal: Generic Post-closure Safety Assessment. Nuclear Decommissioning Authority Report NDA/RWMD/030.Google Scholar
Nuclear Decommissioning Authority(2010b) Geological Disposal: Generic Disposal Facility Designs. Nuclear Decommissioning Authority Report NDA/ RWMD/048.Google Scholar
Parkhurst, D.L. and Appelo, C.A.J. (1999) User’s Guide to PHREEQC (Version 2) - A Computer Program for Speciation, Batch Reaction, One-dimensional Transport and Inverse Geochemical Calculations. US Geological Survey Water-resources Investigations Report 99–4259. US Geological Survey, Reston, Virginia, USA.Google Scholar
Serco (2007) CONNECTFLOW Technical Summary, Release 9.5 . Serco Report SA/ENV/ CONNECTFLOW/15.Google Scholar
Swift, B.T., Bamforth, P.B., Hoch, A.R., Jackson, C.P., Roberts, D.A. and Baston, G.M.N. (2010) Cracking, Flow and Chemistry in NRVB. Serco Report SERCO/TAS/000505/001 (Issue 3).Google Scholar
Walker, C.S., Savage, D., Tyrer, M. and Ragnarsdottir, K.V. (2007) Non-ideal solid solution aqueous solution modeling of synthetic calcium silicate hydrate. Cement and Concrete Research, 37, 502–511.CrossRefGoogle Scholar
Worthington, J., Bamforth, P.B., Price, W.F., Widdows, J. and Field, S.N. (1991) Development of Backfill for Deep Repository Vaults, Stage 2 Report, Laboratory Testing Programme. United Kingdom Nirex Ltd Report No. 129.Google Scholar