Permeability chracterization of nearly impermeable rock masses for nuclear waste repository siting

Characterization of the deep geologic formations now being considered for disposal of long lived radioactive waste requires the development of a wide range of tools for measurement and interpretation of very low permeabilities. A methodology is presented in this paper for measuring such low permeabilities and interpreting the results in terms of the regional hydrology. Small-scale tests on single fractures are proposed to statistically identify the geometrical parameters required for risk analysis of repository safety. Large-scale tests over large volumes of rock containing many fractures should also be conducted to provide direct information on regional permeabilities and to provide a verification of permeabilities inferred from the small-scale tests