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Measurements of Eh and pH in Compacted MX-80 Bentonite

Published online by Cambridge University Press:  19 October 2011

Torbjörn Carlsson  and
Arto Muurinen
Torbjörn Carlsson
Affiliation:
torbjorn.carlsson@vtt.fi, VTT Technical Research Centre of Finland, Nuclear Energy, Otakaari 3A, Espoo, FI-02044 VTT, Finland, +358 40 8390270, +358 20 722 6390
Arto Muurinen
Affiliation:
arto.muurinen@vtt.fi, VTT Technical Research Centre of Finland, Otakaari 3A, Espoo, FI-02044 VTT, Finland
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Abstract

The low-content free water and high swelling pressure in compacted bentonite, planned to be used as a buffer in nuclear waste repositories, create adverse conditions for direct measurements of the chemical conditions. This paper presents laboratory results from online measurements with Eh and pH electrodes in water-saturated compacted MX-80 bentonite. The Eh was measured with Au and Pt wires as electrodes, while the pH was determined with IrOx electrodes. The latter were prepared in accordance with the method by Yao et al. [1]. The measurements were carried out in two types of cells: 'squeezing cells' and 'diffusion cells'. The squeezing cell excludes almost completely all chemical interactions between the sample and the surrounding environment outside the cell. The diffusion cell, on the other hand, contains a sample that stays in contact with an external solution and therefore allows following of the physico-chemical interaction between the sample and the external solution. The measuring electrodes were positioned inside the cell in the compacted bentonite, while the reference electrode was positioned outside the cell.

Keywords

chemical reactionporositywaste management
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 985: Symposium NN – Scientific Basis for Nuclear Waste Management XXX , 2006 , 0985-NN13-09
Copyright
Copyright © Materials Research Society 2007

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