Mass Transfer & Porous Media (MTPM) - Andra

P/MTPM/17Figure 1: Experimental HTO spread at four different horizontal planes (from left to right, 6 to 8 cm, 8 to10 cm, 10 to 12 cm and 12 to 14 cm).synthetic solution representative of the site groundwater (T. Melkior, 2004). TD diffusion experimentswere performed with HTO (neutral), 36 Cl - (anionic) and 22 Na + (cationic) as tracers.In the large-scale diffusion experiments, a re-compacted clay/radionuclide mixed solid source was placedin the centre of a large clay block, allowing the tracer to diffuse into the closed system. At the end, athorough sampling of the rock provided a 3D distribution of the tracer activity, evidencing the diffusionpaths. Experiments using HTO and 85 Sr 2+ were finished but experiments with 137 Cs + , 60 Co 2+ and 152 Eu 3+ arestill ongoing. Figure 1 show HTO experimental results obtained at four different horizontals planes.These experiments demonstrated that the methodology proposed for large-scale diffusion studies isfeasible. Results showed that it is possible to obtain a good three-dimensional representation of thediffusion process that allows analysing the anisotropy of diffusion.The proposed experimental set-up could simplify the design and performance of an in situ diffusionexperiment, eliminating the need for continuous monitoring and avoiding the alteration of the clay (due tocontact with water) in the proximity of the source of the tracer.ACKNOWLEDGEMENTSThis work has been carried out in the frame of the ENRESA-CIEMAT association and partially funded bythe EU within the FUNMIG (Fundamental Processes of radionuclide Migration) Project (Ref. FP6-516514).References:Gaussen, J.-L. (2002): Bure’s Underground Research Laboratory. General framework. Objectives. Sitingprocess and schedule, JNC’s conference.García-Gutiérrez, M., Cormenzana, J.L., Missana, T., Mingarro, M., Martín, P.L. (2006): “Large-scalelaboratory diffusion experiments in clay rocks” Physics and Chemistry of the Earth 31, 523–530.Melkior, T., (2004): Personal communication.Page 456INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT