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A coupled non-isothermal reactive transport model for long-term geochemical evolution of a HLW repository in clay

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Environmental Geology

Abstract

A numerical model of coupled saturated/unsaturated water flow, heat transfer and multi-component reactive solute transport is presented to evaluate the long-term geochemical evolution in bentonite, concrete and clay formation for a potential geological radioactive waste repository. Changes in formation porosity caused by mineral dissolution/precipitation reactions are taken into account. Simulations were carried out with a general-purpose multicomponent reactive transport code, CORE2D V4. Numerical results show that pH in the bentonite porewater can vary from neutral to up to 13 over a time scale of 1 Ma although dissolution of silica minerals and precipitation of secondary calcium silicate hydrate (CSH) minerals in bentonite buffer the effect of the hyperalkaline plume. Mineral precipitation reduces the volume of pore space in bentonite close to the bentonite–concrete interface due to the precipitation of CSH minerals. Model results indicate that bentonite porosity decreases less than 25%. The hyperalkaline plume from the concrete only extends to a distance of 0.7 m in the clay formation over the time range of 1 Ma.

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Acknowledgments

This work was supported by the Spanish Nuclear Waste Company (ENRESA) through contracts #770045 and 770125, the European Union through Project NF-PRO (FI6W-CT-2003-02389), the Spanish Ministry of Science and Technology (CICYT Projects HID98-282 and REN 2003-8882), Xunta de Galicia (Incentive PGIDT04PXIC11801PM) and the University of La Coruña through a research scholarship awarded to the first author. We acknowledge the contribution of Qingchun Yang for sensitivity calculations. The authors also thank the constructive comments from the anonymous reviewers.

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  1. Escuela de Ingenieros de Caminos, Canales y Caminos Universidad de A Coruña, A Coruña, Spain

    Changbing Yang, Javier Samper & Luis Montenegro

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  1. Changbing Yang
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  2. Javier Samper
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  3. Luis Montenegro
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Correspondence to Changbing Yang.

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Yang, C., Samper, J. & Montenegro, L. A coupled non-isothermal reactive transport model for long-term geochemical evolution of a HLW repository in clay. Environ Geol 53, 1627–1638 (2008). https://doi.org/10.1007/s00254-007-0770-2

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  • DOI: https://doi.org/10.1007/s00254-007-0770-2

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