Abstract:
In order to assess the performance of radioactive waste repository, the investigation of gas migration process through the formation of fully water-saturated Cox argillite is indispensable. Traditional methods, based on macroscopic approaches or homogeneous transport properties, are inappropriate to analyze this issue at the meso/microscopic scale. In this study, using the experimental pore size distribution curve, the morphological aspect of porous network is represented by the excursion of Gaussian Random Field. Essentially, the extraction of accessible pores for a given gas pressure is feasible via the morpho-mathematical transformations. This modeling work focuses on the estimation of capillary induced breakthrough pressure and the identification of adequate gas transport mechanisms for breakthrough process.
Introduction
Argillite is a privileged candidate material in the context of radioactive waste disposal for its low permeability and deeply seated formation. In France, Callovo-Oxfordian argillites are in large quantities in departments of Haute-Marne and Meuse [1]. An underground research laboratory, built by ANDRA (French National Radioactive Waste Management Agency) on the site of Bure, is to investigate the properties of host rocks and to assess the storage performance of long-lived radioactive waste.
Particularly, for a long period, the low-permeable repository formation will produce a significant amount of hydrogen gas due to humid corrosion of metallic parts, coupled to radioactive waste decay and radiolysis of water [2]. If the generated gas is not able to transfer, after a long period of accumulation, the increasing gas pressure may create micro-cracks and fracture the compacted clay rock. Meanwhile, during the accumulation process, if the gas pressure can overcome the capillary resistance, hydrogen gas will leak from the structure. Consequently, the investigation of gas transport is of high relevance in the assessment of repository performance.
