Determination of the Porosity, Permeability and Diffusivity of Rock in the Excavation-Disturbed Zone Around Full-Scale Deposition Holes Using the He-Gas Method

Abstract

In a nuclear waste repository, rock in the excavation-disturbed zone adjacent to the walls of deposition holes for waste canisters is a potential pathway for the transport of corrosive agents and radionuclides. Three experimental holes the size of deposition holes in a KBS-3 type repository (depth 7.5 m and diameter 1.5 m) were bored in hard granitic rock in the Research Tunnel at Olkiluoto and the porosities, effective diffusivities and permeabilities of rock in the excavation-disturbed zone were determined in a direction parallel to the disturbed surface using He-gas methods. Permeability and diffusivity in a direction parallel to the rock schistosity was found to be clearly larger than in a direction perpendicular to it.

Matrix diffusion and sorption of Cs+, Na+, I– and HTO in granodiorite: Laboratory-scale results and their extrapolation to the in situ condition

“…Samples used for laboratory experiments are typically centimetre scale and are generally taken from drillcores. The process of drilling and subsequent sample treatment for laboratory testing can create new cracks and microcracks through stress release and disturbance (e.g., Autio et al, 1998;Bradbury and Stephen, 1986; Skagius and Neretnieks, 1986; Tullborg and Larson, 2006;Vilks et al, 2003). Increased porosity values in laboratory samples due to artificially disturbed conditions compared to in situ conditions have been well documented in previous studies (e.g., Jokelainen et al, 2013;Ota et al, 2003; Tullborg and Larson, 2006).…”