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CO2 effect on the pH of compacted bentonite buffer on the laboratory scale

Published online by Cambridge University Press:  09 July 2018

A. Itäla ,
J. Järvinen  and
A. Muurinen
A. Itäla
Affiliation:
VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland
J. Järvinen
Affiliation:
VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland
A. Muurinen
Affiliation:
VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT, Finland
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Abstract

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Disposal of Finnish spent nuclear fuel is planned to be based on the KBS-3 repository concept. The role of the bentonite buffer in this concept is essential, and thus the behaviour of the bentonite has to be known. The experiments in this paper concentrated on providing information about the effects of carbon dioxide CO2(g) partial pressure on compacted sodium bentonite, giving an insight into the buffering capacity. The experimental setup consisted of a hermetic box which had a CO2-adjusted atmosphere, and the bentonite was in contact with this atmosphere through water reservoirs. The results indicated that it is possible to measure online the changing pH in the porewater inside compacted bentonite using IrOx electrodes. It was found that the pH fell if the CO2 partial pressure increased above atmospheric conditions. The experimental results indicated a greater fall in pH than in our model in the test cases where CO2 was present. The pH in the experiment with 0 PCO2 remained nearly constant throughout the 5 month period. On the other hand, the pH dropped to near 6 with 0.3 PCO2 and to 5.5 with 1 PCO2.

Keywords

bentonitepHcarbon dioxidebufferalterationcompaction
Type
Research Article
Information
Clay Minerals , Volume 48 , Issue 2 , May 2013 , pp. 277 - 284
Creative Commons
Creative Common License - CCCreative Common License - BY
Copyright © The Mineralogical Society of Great Britain and Ireland 2013 This is an Open Access article, distributed under the terms of the Creative Commons Attribution license. (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

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