Sensitivity of Pressurized Water Reactors Vessels Aging to Fuel Composition
Résumé
The operation of many French nuclear 900 MWe Pressurized Water Reactors (PWR) is being extended beyond their design lifetime. In the perspective of further extension, the evaluation of reactor pressure vessels (RPV) aging is of great importance. The embrittlement of the vessel is mainly induced by fast neutron irradiation (neutrons with energies above 1 MeV). Consequently, the fast neutron fluence is one of the quantities used by safety authorities to characterize the structural integrity of the RPV. Estimates of this quantity are based on evaluations of the fast neutron flux that can be performed by a two-step approach. The first step estimates the full core fission neutron source term and the second step models the transport of neutrons from the core to the RPV using the fission neutron distribution determined in the previous step. Such fast neutron flux evaluations are subject to bias and uncertainties, which must be precisely analyzed in order to enhance nuclear safety. Especially, a lack of knowledge in fuel composition can have a significant impact on the quantification of the fast neutron flux, since it may impact both steps of the calculation. Therefore, this study proposes to discuss the sensitivity of fast neutron flux assessments to perturbations of nuclear fuel composition. The analysis has been performed using a deterministic code (CASMO5) to compute the fission neutron source term and a Monte-Carlo model (MCNP6) to compute the neutron attenuation.
Domaines
Physique [physics]Origine | Fichiers produits par l'(les) auteur(s) |
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