[en] In Stage 2 of the Sectoral Plan for Deep Geological Repositories, safety analyses have to be performed. Geochemical parameters describing the transport and retardation of radionuclides in the argillaceous rocks considered and in compacted bentonite are required. In the present report, diffusion parameters for all clay host rocks, confining units and compacted bentonite are derived. Diffusion of tritiated water (HTO), "3"6Cl"- and "2"2Na"+ was studied. The measurements gave values for effective diffusion coefficients (D_e) and diffusion accessible porosities. The general observed trend "N"aD_e > "H"T"OD_e > "C"lD_e is in agreement with the expected behaviour of the three species in clay materials: ion exchanging cations show an enhanced mobility due to surface diffusion effects and anions are slowed down due to anion exclusion. Due to the negatively charged clay surfaces, anionic species are repelled from these surfaces resulting in an accessible porosity that is smaller than the total porosity as measured with HTO. The effect of porewater composition on the diffusion of HTO, "3"6Cl"- and "2"2Na"+ in Opalinus Clay was investigated. For ionic strength (IS) values between 0.17 M and 1.07 M, no significant effect on D_e could be observed. In the case of "3"6Cl"-, no effect on the accessible porosity was observed. The anion diffusion accessible porosity equals 50-60 % of the total porosity, independent on the ionic strength of the porewater. The diffusion parameters were measured on sedimentary rocks such as chalk, clay and limestone rocks. All data could be described by one single modified version of Archie's relation (extended Archie's relation). For values of porosity greater than about 0.1, the classical Archie's relation was valid. For values smaller than 0.1, the data deviated from the classical Archie's relation; this can be explained by additional changes of tortuosity with porosity values. At high porosity values (low density rocks), the microfabric of the clay rock is of a house-of-cards type. With increasing density, the randomly oriented clay platelets become more oriented in a specific direction perpendicular to the direction of compaction. As soon as the platelets are more or less horizontally oriented, further decrease of the porosity has no longer an effect on the orientation and consequently on the tortuosity. The rock bulk dry density threshold value is about 2500 kg m"-"3, representing a porosity value of 0.1. Important input parameters are the diffusion coefficient of the radionuclides in free bulk water and the transport relevant porosity. Radionuclides were subdivided into two main groups with a free water diffusion coefficient of (20.0 ± 2.5) x l0"-"1"0 m"2 s"-"1 and (7.5 ± 2.5) x 10"-"1"0 m"2 s"-"1. The porosities were derived mainly from drilling core samples of the host rocks by measurements of the bulk and grain density of the rocks. The values for anion accessible porosities were based on the observation that for most clay rocks about 50 % of the total porosity is accessible to anions. In case of cations undergoing ion exchange, a correction factor CF was calculated using the surface mobility of the cation and the sorption values. The reference values of the effective diffusion coefficients, and their upper and lower bounding values, were multiplied with these correction factors. For most clay rocks investigated, the correction factors used ranged from 1 to at most 30, depending on the sorption value of the cation. The largest values were calculated for Cs"+. In case of Helvetic Marls, the correction factors were between 30 and 400. This is caused by the much larger capacity ratio values, which are directly proportional to the reciprocal transport porosity of the clay rocks. As the depth of the host rocks varies notably in the siting regions, a temperature range was defined for each potential host rock. Effects of temperature on diffusion were evaluated using the Arrhenius equation with an average activation energy for diffusion of 22.9 kJ/mol. For each host rock, a table with effective diffusion coefficients was compiled; the tables contain a reference value at 25 °C calculated for the reference porosity. Upper and lower values were estimated by combining the upper e-Archie's curve with the upper value for porosity, and the lower e-Archie's curve with the lower value for porosity. A combined uncertainty on porosity and temperature was estimated by error propagation