Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4721626 | Physics and Chemistry of the Earth, Parts A/B/C | 2008 | 12 Pages |
Abstract
Two and three-dimensional modeling has been performed using the CRUNCH and CORE3D reactive transport codes, respectively. The experimental setup favored, in principle, a 2D interpretation of the results, since diffusion occurs mainly along bedding planes. Conservative tracers from 2D modeling gave: De|| = 5.0 Ã 10â11 m2/s, Ï = 0.16 (HDO) and De|| = 1.2 Ã 10â11 m2/s, Ï = 0.09 (Iâ). Results from 3D modeling are: De|| = 4.0 Ã 10â11 m2/s, De||/Deâ¥Â = 4, Ï = 0.15 (HDO) and De|| = 8.3 Ã 10â12 m2/s, De||/Deâ¥Â = 4, Ï = 0.08 (Iâ). Differences in the results may be due to the two geometries (3D / 2D), to various aspects of the calculations or to comparison methods between model and experimental data. A previous sensitivity analysis performed with the 3D model had shown that the effect of considering only diffusion along the bedding planes (De||/Deâ¥Â = 100) was relatively minor, causing only a significant effect on tracer distribution in the rock near the top and bottom edges of the injection interval. The differences between the two sets of results are small and confirm the smaller effective diffusion coefficient and accessible porosity of Iâ with respect to HDO. The results corresponding to 6Li+ and 87Rb+ have also been modeled using both 2D and 3D approaches. For 6Li+ (C0 = 3 Ã 10â5 mol/l), the best fit for both models was achieved with De|| â 7 Ã 10â11 m2/s, Kd â 0.2 l/kg and Ï = 0.15-0.16. The De and Kd values are very similar to those obtained previously for Na+ at Mont Terri. This Kd value is certainly larger than what was initially expected. Regarding 87Rb+ (C0 = 3 Ã 10â7 mol/l), only three profiles were finally measured, and they showed significant variability. This variability has also been observed for other strongly sorbing tracers (Cs+, Co2+) in the DI-A and DI-A2 in situ experiments at Mont Terri. It has not been possible to obtain unique values for De|| and Kd for 87Rb+, although strong sorption has been confirmed.
Related Topics
Physical Sciences and Engineering
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Authors
J.M. Soler, J. Samper, A. Yllera, A. Hernández, A. Quejido, M. Fernández, C. Yang, A. Naves, P. Hernán, P. Wersin,