Reactive transport modeling of the clogging process at Maqarin natural analogue site |
| |
| Institution: | 1. Research Institute for Groundwater, National Water Research Center, Cairo, Egypt;2. School of Geosciences, University of South Florida, Tampa, FL, USA;1. Quintessa Ltd., 633/635 Birchwood Boulevard, Warrington WA3 6QU, United Kingdom;2. Quintessa Ltd., The Hub, 14 Station Road, Henley-on-Thames, Oxfordshire RG9 1AY, United Kingdom;1. Geological Isolation Research and Development Directorate, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1194, Japan;2. Laboratory of Environmental Geology, Faculty of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan |
| |
| Abstract: | The Maqarin site in Jordan has been investigated for three decades as a natural analogue for the long term changes of materials in contact with hyper-alkaline solutions. Similar processes are expected in radioactive waste disposal sites, where cement based materials are in contact with natural rocks or other e.g. clay based materials. In this context, a numerical reactive transport model was used to study local geochemical alterations and induced porosity changes for the Maqarin marl rock in contact with the hyper-alkaline solution. The geochemical setup for the rock mineralogy and the pore water was calibrated to match measurements from the Maqarin site. The setup includes several clay and zeolite minerals, considers cation exchange processes, and a state-of-the-art model for cement phases. Similar to earlier calculations by Steefel and Lichtner (1998) who used a much simpler geochemical model, the pore clogging occurred after several hundred years at a distance of 5–10 mm from the contact to the hyper-alkaline solution. In our calculations, this was caused by a massive precipitation of ettringite and C–S–H minerals. We performed a sensitivity study by varying the intrinsic diffusion coefficient, the Archie’s law exponential factor, and the mineral surface area available for dissolution and precipitation. We found that the dissolution of clay minerals controls the availability of Al, which is needed for ettringite and C–S–H phase precipitation. Thus, the amount and kinetically controlled dissolution of clay minerals controls the spatial and temporal evolution of porosity changes. The simulations reveal that neither cation exchange processes nor the formation of zeolite minerals strongly influence the geochemical evolution of the system. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
