Matrix diffusion of simple cations, anions, and neutral species in fractured crystalline rocks

The diffusion of radionuclides into the pore spaces of a rock matrix and the pore properties in fractured crystalline rocks were investigated. Through-diffusion experiments were conducted to obtain effective and apparent diffusion coefficients for Na⁺, Cs⁺, HTO, Cl^- and SeO₃^2- as a function of ion charge through the fracture fillings, and altered and intact granodiorite of the Kamaishi In Situ Test Site. The total porosity, density, pore-size distribution, and specific surface area of the pores of the rocks were determined by water saturation method and Hg porosimetry. The formation and geometric factors of the rocks were evaluated by normalizing the free water diffusion coefficient for each species.