Moyce, E.B.A., Rochelle, C., Morris, K. et al. (5 more authors) (2014) Rock alteration in alkaline cement waters over 15 years and its relevance to the geological disposal of nuclear waste. Applied Geochemistry, 50. pp. 91-105. ISSN 1872-9134
Abstract
The interaction of groundwater with cement in a geological disposal facility (GDF) for intermediate level radioactive waste will produce a high pH leachate plume. Such a plume may alter the physical and chemical properties of the GDF host rock. However, the geochemical and mineralogical processes which may occur in such systems over timescales relevant for geological disposal remain unclear. This study has extended the timescale for laboratory experiments and shown that, after 15 years two distinct phases of reaction may occur during alteration of a dolomite-rich rock at high pH. In these experiments the dissolution of primary silicate minerals and the formation of secondary calcium silicate hydrate (C–S–H) phases containing varying amounts of aluminium and potassium (C–(A)–(K)–S–H) during the early stages of reaction (up to 15 months) have been superseded as the systems have evolved. After 15 years significant dedolomitisation (MgCa(CO3)2 + 2OH ? Mg(OH)2 + CaCO3 + CO3(aq) 2 ) has led to the formation of magnesium silicates, such as saponite and talc, containing variable amounts of aluminium and potassium (Mg–(Al)–(K)–silicates), and calcite at the expense of the early-formed C–(A)–(K)–S–H phases. This occured in high pH solutions representative of two different periods of cement leachate evolution with little difference in the alteration processes in either a KOH and NaOH or a Ca(OH)2 dominated solution but a greater extent of alteration in the higher pH KOH/NaOH leachate. The high pH alteration of the rock over 15 years also increased the rock’s sorption capacity for U(VI). The results of this study provide a detailed insight into the longer term reactions occurring during the interaction of cement leachate and dolomiterich rock in the geosphere. These processes have the potential to impact on radionuclide transport from a geodisposal facility and are therefore important in underpinning any safety case for geological disposal.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/3.0/). |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Engineering (Sheffield) > Department of Civil and Structural Engineering (Sheffield) |
Funding Information: | Funder Grant number NATURAL ENVIRONMENT RESEARCH COUNCIL NE/H006540/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 29 Mar 2018 11:10 |
Last Modified: | 29 Mar 2018 11:10 |
Published Version: | https://doi.org/10.1016/j.apgeochem.2014.08.003 |
Status: | Published |
Publisher: | Elsevier |
Refereed: | Yes |
Identification Number: | 10.1016/j.apgeochem.2014.08.003 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:129003 |