The micro flow channel method was utilized for the in-situ determination of both effective diffusion and distribution coefficients by attaching of the tinny flow channel on the borehole wall excavated in a granite formation. Three different solutes such as deuterium oxide D 2 O, uranine and potassium ion K + were injected simultaneously into the rock matrix, then the breakthrough curves had been obtained and analyzed by numerical means. The effective diffusion coefficients D e of non-sorbing solutes (D 2 O, uranine) as well the distribution coefficient of sorbing solute (K +) were obtained at the intact surface were in good accordance with the reported values.On the other hand, the observation at the surface with a single crack gave different breakthrough patterns and the D e s for the non-sorbing solutes were greater than those at the intact surface about one order of magnitude. Even if the crack opening was small, less than 0.5 mm, the tin crack might cause the overestimation of the matrix diffusivity. Through the in-situ experiments, the method enables us to quick and simultaneous estimates of the important parameters for the nuclide migration analysis.

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