An experimental methodology to assess the impact of desaturation on gas diffusion in clay based materials

The transport of gas in clay-based materials is dominated by diffusion. SCK CEN has studied and recorded an extensive data set diffusion coefficients gases various saturated clays (Boom Clay, Opalinus Callovo-Oxfordian claystone bentonites) used Europe as host formations or engineered barrier systems the context deep geological disposal high intermediate level nuclear wastes. However, partially conditions may exist during life cycle a radioactive waste repository. current study aims at establishing experimental method to measure means double through tests (cross across porous sample, driven concentration gradients) assess impact desaturation on diffusivity. Historically, measurements have been performed under dissolved with continuous water flow around clay sample. since saturation degree sample be constant, novel setup designed optimized operate pure phase controlled relative humidity (RH). concept consists cross mixtures from two reservoirs fixed either side cell, namely, upstream downstream reservoirs. RH using same salt solutions both During experiment, will diffuse reservoir. By measuring change composition reservoir analyzer equipped mass spectrometer (which expresses terms partial pressure), flux hence coefficient estimated applying steady state Fick’s first law. methodology validated performing experiment sandy-clay known petrophysical properties, full saturation.