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In situ anion diffusion experiments using radiotracers
KTH, Superseded Departments, Chemistry.
KTH, Superseded Departments, Chemistry.
2004 (English)In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 68, no 3-4, 183-192 p.Article in journal (Refereed) Published
Abstract [en]

Diffusion experiments in compacted bentonite have been carried out in situ using the borehole laboratory CHEMLAB. The ordinary anion iodide and the redox-sensitive pertechnetate ion have been investigated. In spite of strongly reducing groundwater conditions, technetium was found to diffuse mostly unreduced as TcO4-, although in some spots in the compacted clay, the activity was significantly higher, which may be explained by reduction of some TcO4- by iron-containing minerals in the bentonite. The measured concentration profiles in the clay cannot be accommodated by assuming one single diffusion process. The experimental data are modeled assuming two diffusion paths, intralamellar diffusion and diffusion in external water. The apparent diffusivity for the intralamellar diffusion was found to be 8.6 x 10(-11) m(2) s(-1) for iodide with a capacity factor of 0.1, while the apparent diffusivity for the diffusion in external water was found to be 5 x 10(-14) m(2) s(-1) with alpha = 2.26. The corresponding values for Tc were found to be D-a = 6 x 10(-11) m(2) s(-1), alpha = 0.1 and D-a = 1 x 10(-13) m(2) s(-1), alpha = 0.46, respectively. The diffusion constants and capacity factors obtained in this study are in accordance with data from laboratory experiments.

Place, publisher, year, edition, pages
2004. Vol. 68, no 3-4, 183-192 p.
Keyword [en]
in situ, diffusion, CHEMLAB, bentonite, anion, iodide, pertechnetate, bentonite clay, compacted bentonite, technetium, pertechnetate, reduction, products, iron, fuel
National Category
Environmental Sciences
URN: urn:nbn:se:kth:diva-23138DOI: 10.1016/s0169-7722(03)00149-9ISI: 000188737600003PubMedID: 14734245ScopusID: 2-s2.0-0345743491OAI: diva2:341836
QC 20100525 QC 20111031Available from: 2010-08-10 Created: 2010-08-10 Last updated: 2011-10-31Bibliographically approved

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