Nuclear glass alteration bridging the gap from surface reactivity description to reactive transport at the scale of the fractured block

Abstract : The complete workflow comprising the steps of image analysis, tessellation construction and upscaling of permeability and diffusion coefficients is elaborated in order to prepare an equivalent mathematical model of a nuclear glass package at scale 1 for further reactive transport modelling. The workflow asks as input the pre-prepared grayscale image and progresses through five stages- (i) fracture network extraction, (ii) image segmentation and fracture aperture measuring, (iii) crystals ' anisotropy characterization, (iv) construction of an equivalent tessellation and (v) determination of equivalent fields of permeability and diffusion. Images of the longitudinal cross-sections of two specimens of non-radioactive packages of vitrified glass are used as a testbed for this study. Imaged packages were produced at the Vitrification Production Facilities in Marcoule in a cold crucible induction melter, with UOx package being a close analogue of the French R7T7 nuclear glass.We provide the implementation of the complete routine and demonstrate the results obtained via the image analysis and steps of upscalling.