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The initial dissolution rates of simulated UK Magnox–ThORP blend nuclear waste glass as a function of pH, temperature and waste loading

Published online by Cambridge University Press:  02 January 2018

N. Cassingham
Affiliation:
Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, UK
C.L. Corkhill*
Affiliation:
Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, UK
D.J. Backhouse
Affiliation:
Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, UK
R.J. Hand
Affiliation:
Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, UK
J.V. Ryan
Affiliation:
Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington, USA
J.D. Vienna
Affiliation:
Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington, USA
N.C. Hyatt*
Affiliation:
Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, UK
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Abstract

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The first comprehensive assessment of the dissolution kinetics of simulant Magnox–ThORP blended UK high-level waste glass, obtained by performing a range of single-pass flow-through experiments, is reported here. Inherent forward rates of glass dissolution were determined overa temperature range of 23 to 70°C and an alkaline pH range of 8.0 to 12.0. Linear regression techniques were applied to the TST kinetic rate law to obtain fundamental parameters necessary to model the dissolution kinetics of UK high-level waste glass (the activation energy (E a),pH power law coefficient (η) and the intrinsic rate constant (k0)), which is of importance to the post-closure safety case for the geological disposal of vitreous products. The activation energies based on B release ranged from 55 ± 3 to 83 ± 9 kJ mol–1,indicating that Magnox–THORP blend glass dissolution has a surface-controlled mechanism, similar to that of other high-level waste simulant glass compositions such as the French SON68 and LAW in the US. Forward dissolution rates, based on Si, B and Na release, suggested that the dissolutionmechanism under dilute conditions, and pH and temperature ranges of this study, was not sensitive to composition as defined by HLW-incorporation rate.

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Type
Research Article
Creative Commons
Creative Common License - CCCreative Common License - BY
Copyright © The Mineralogical Society of Great Britain and Ireland 2015. This is an open access article, distributed under the terms of the Creative Commons Attribution (CC BY) license (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 2015