3D simulation of a power ramp including oxygen thermo-diffusion and its impact on thermochemistry

Abstract

International audienceThis paper presents the coupling of the thermochemical solver ANGE (Advanced Gibbs Energy Minimizer) with an oxygen thermo-diffusion model. The coupling is implemented within the fuel performance code ALCYONE co-developed by CEA, EDF and FRAMATOME within the PLEIADES environment. An application to a 3D simulation of a power ramp on a Cr-doped UO 2 fuel is developed. Post-ramp EPMA measurements of chromia doped fuel show reduction of chromium and molybdenum oxides in the central part of the pellet, indicative of thermo-diffusion of oxygen. These phenomena are well reproduced by the coupled thermo-chemical-mechanical simulations. Impact of oxygen redistribution on speciation of fission products is then studied. Chemical state of caesium, iodine and tellurium is important as regard PCI, as they can form gaseous species (CsI$_{(g),}$ I $_{(g),}$ I$_{(2g),}$ TeI$_{(2g)}$) that can react with the cladding and induce SCC. Release of gaseous species and concentration of chemically reactive iodine compounds near the cladding are calculated in order to investigate I-SCC