A coupled non-isothermal reactive transport model for long-term geochemical evolution of a HLW repository in clay |
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| Authors: | Changbing Yang Javier Samper Luis Montenegro |
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| Institution: | 1.Escuela de Ingenieros de Caminos,Canales y Caminos Universidad de A Coru?a,A Coru?a,Spain |
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| 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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| Keywords: | Geochemistry Waste management Geoscience |
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