Mass Transfer & Porous Media (MTPM) - Andra

P/MTPM/31Furthermore, Van Loon et al. (2003) studied effective diffusion coefficients of tritiated water (HTO) inOpalinus Clay and compared their results with effective diffusion coefficients of HTO for a series ofargillaceous rocks (e.g. London Clay, Boom Clay, Wellenberg Marl, Tournemire Toarcian shale). Theyconcluded that the effective diffusion coefficients can be satisfactorily described using Archie’s law withan exponent of around 2.5.DATA ANALYSISBoth dissimilar data sets (Grathwohl, 1998; Van Loon et al., 2003) indicate that Archie’s law might beapplied for the estimation of the effective diffusion coefficients in argillaceous rocks. However, the valueof the accessible or transport-through porosity, respectively, is often not known and therefore Archie’s lawwill result in imprecise estimates for effective diffusion coefficients. Hence, in the current study, data oneffective diffusion coefficients and transport porosities will be collected from diffusion studies (e.g.Henrion et al., 1991; De Cannière et al., 1996; Decostes et al., 2007) performed on various argillaceousrocks (e.g. Opalinus Clay, Callovo-Oxfordian argillites and Boom Clay).RESULTS AND INTERPRETATIONComprehensive data sets on diffusion of different tracers (anions, cations and neutral species) inargillaceous rocks will be presented and the applicability of Archie’s law for clays and clay stones will bethoroughly discussed in context of the diffusion (or transport) accessible porosity. The relevance for safetyassessment of potential radioactive waste repositories will be highlighted.References:Blum, P. (2000): “Sorption- and diffusion behaviour of organic compounds in Israelian and EuropeanChalk“. MSc-Thesis, Applied Geology, University of Karlsruhe.Boving, T.B., Grathwohl, P. (2001): “Tracer diffusion coefficients in sedimentary rocks: correlation toporosity and hydraulic conductivity”. Journal of Contaminant Hydrology, 53, 85-100.De Cannière P., Moors H., Lolivier P., De Preter P., Put M. (1996): “Laboratory and in situ migrationexperiments in Boom Clay”. Nuclear Science and Technology, EUR16927, EC, Luxembourg.Descostes, M., Blin, V., Bazer-Bachi, F., Meier, P., Grenut, B., Radwan, J., Schlegel, M.L, Buschaert, S.,Coelho, D., Tevissen, E. (2007): “Diffusion of anionic species in Callovo-Oxfordian argillites andOxfordian limestones”. Submitted to Applied Geochemistry.Grathwohl, P. (1998): “Diffusion in Porous Media”. Kluwer Academic Publishers, London.Henrion, P.N., Put, M.J., Van Gompel, M. (1991): “The influence of compaction on the diffusion of nonsorbedspecies in Boom Clay”. Radioactive Waste Management and the Nuclear Fuel Cycle, 16 (1), 1-14.Van Loon, L.R., Soler, J.M., Jakob, A., Bradbury, M.H. (2003): “Effect Effect of confining pressure on thediffusion of HTO, 36 Cl − and 125 I − in a layered argillaceous rock (Opalinus Clay): diffusion perpendicularto the fabric”. Applied Geochemistry, 18, 1653-1662.Page 484INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT