Reactive Transport of Chemicals in Compacted Bentonite under Nonisothermal Water Infiltration
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 144, Issue 10
Abstract
This paper presents an investigation of coupled thermal, hydraulic, and chemical behavior of a compacted bentonite buffer under the heating and hydration conditions of geological disposal of high-level nuclear waste. The study presented provides further insight into the evolution of hydro-geochemistry of the compacted bentonite and the clay microstructure effects through a numerical modelling development of the reactive transport of multicomponent chemicals. The application/validation case study is based on a series of laboratory tests on heating and hydration of compacted bentonite for a period of 0.5–7.6 years reported in the literature. The effects of microstructure evolution during hydration and dehydration on the transport phenomena are included via a new approach that links the geochemistry of clay hydration/dehydration with the transport properties. The analysis results related to the moisture flow and chloride transport demonstrate close correlation with the experimental results by the inclusion of the effects of microstructure evolution in the transport phenomena. The results of numerical analysis of reactive transport of chemicals highlight the importance of accessory minerals present in bentonite on the distribution of some anionic species. The behavior of major cationic species is shown to be mainly governed by the transport processes. Further insights into the chemically driven processes in clay buffer due to coupled hydraulic and thermal effects are presented and discussed that are captured from the results of modeling the clay-water-chemical system.
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Acknowledgments
The financial support received by the first author in the form of a PhD scholarship from the UK’s Overseas Research Students Awards Scheme (ORSAS) is gratefully acknowledged. The support and contribution from Dr Suresh C. Seetharam (former Research Fellow at Cardiff University and currently a Scientist at the Belgian Nuclear Research Centre) in the early stages of this research is also gratefully acknowledged.
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Journal of Geotechnical and Geoenvironmental Engineering
Volume 144 • Issue 10 • October 2018
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©2018 American Society of Civil Engineers.
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Received: Nov 7, 2016
Accepted: Apr 26, 2018
Published online: Aug 11, 2018
Published in print: Oct 1, 2018
Discussion open until: Jan 11, 2019
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