French alternative energies and atomic energy commission (CEA) is still studying a sodium fast reactor (SFR) core with intrinsic safety . In this reactor core, low linear heat rate induce a significant fission gas retention in the fuel. It is mandatory to describe accurately the thermomechanics of this concept in order to confirm its safety.
Current model used in the CEA as fuel performance code for SFR, GERMINAL, is based on an empirical approach which the calibration database is centered on fuel pins irradiated at a high linear heat rate, and also a low gas retention. This fellow aims to extend to SFR fuels an existing gas model, MARGARET, which has been developed for the pressurized water reactor (PWR) fuels. On issue will be the restructuring phenomenon, which is far more relevant in SFR than in PWR, this topic is raised in .
First step of the work will consist in the integration of the MARGARET gas model in the GERMINAL code throughout the PLEIADES platform. This task will need to couple variables associated to the resolution of equilibriums in various physics (thermal, mechanical, and gas swelling) in order to build the coupling scheme.
Second step of the work will be focused on the analysis of the mechanisms contributing to the gas swelling, using the post-irradiation experiments realized in the CEA Cadarache facility (LECA - Laboratoire d’Examens des Combustibles Actifs). Image analysis tools would be used in order to characterize the porosity distribution in the fuel. Based on these observations, it will be necessary to make the calibration of the MARGARET model in order to give a good assessment of the gas swelling and of the porosity distribution. Depending on the results, a second year dedicated to the extension of this gas model for the power transients would be possible.