Evaluation of tritiated water diffusion through the Toarcian clayey formation of the Tournemire experimental site (France)

Modeling Coupled Processes in Clay Formations for Radioactive Waste Disposal

“…At large scales, diffusive transport may be subject to a considerable degree of spatial variability as a result of variability of physical and chemical properties of pore spaces. It is also well known that large-scale diffusive process is not isotropic in clay rocks (Motellier, 2007). Diffusion coefficient is much larger along the bedding direction than that in the direction perpendicular to the bedding.…”

“…Although different degrees of successes have been obtained by using the currently available phenomenological approaches to analyze several site-specific tests (e.g., Appelo et al, 2010;Motellier et al, 2007), some key questions regarding their usefulness are open, considering the semi-empirical feature of the approaches. For example, a systematic evaluation of their effectiveness in capturing effects of pore-scale heterogeneities (the existence of different pore spaces) is not available yet for general natural clay systems.…”

Comparison of modeling methods for the determination of effective porosities and diffusion coefficients in through‐diffusion tests

“…[37] It has been widely accepted in literature that the use of the time axis intercept in the TL solution (equation (5)) does not provide a reliable estimate of the effective porosity because the intercept is very sensitive to slight changes in the slope of the best fit line to the experimental data [Grathwohl, 1998;Van Loon et al, 2003a;Appelo and Wersin, 2007;Motellier et al, 2007]. This discrepancy can be seen in Table 2, where the effective porosities derived by this method vary substantially from both the bulk porosities and the effective porosities derived by the SA method.…”

Estimating thermo-osmotic coefficients in clay-rocks: II. In situ experimental approach

“…Permeability measurements parallel and normal to the bedding suggest an anisotropy [31,33,34]. Tritiated water diffusion in Tournemire argillite also indicates an anisotropy: a 1/3 ratio is observed between the HTO effective diffusion normal to the bedding and the one parallel to the bedding [35]. The Tournemire argillite presents clay-rock typical thermal characteristic values: a thermal conductivity of 1.6-1.8 W m À1 K À1 and a specific heat of about 700 J kg À1 K À1 [32].…”