STAGE - Uncertainty quantification of the neutron fluence on a nuclear reactor vessel through core H/F

L'IRSN, Etablissement Public à caractère Industriel et Commercial (EPIC) – dont les missions sont désormais définies par la Loi n° 2015-992 du 17 août 2015 relative à la transition énergétique pour la croissance verte (TECV) – est l'expert public national des risques nucléaires et radiologiques. L'IRSN concourt aux politiques publiques en matière de sûreté nucléaire et de protection de la santé et de l'environnement au regard des rayonnements ionisants. Organisme de recherche et d'expertise, il agit en concertation avec tous les acteurs concernés par ces politiques, tout en veillant à son indépendance de jugement

Extending the operational life of Pressurized Water Reactors (PWR) is a significant concern for the nuclear industry in general and for French 900MWe PWR in particular. Indeed, French 900MWe PWR operation lifetime initially designed for 40 years is planned to be extended to 60 years, and preliminary studies might suggest an extension up to 80 years. The Reactor Pressure Vessel (RPV) plays a key role in this effort, as it is an irreplaceable component, and its integrity is therefore fundamental to reactor safety. Over time, neutron irradiation causes embrittlement in the RPV's steel, increasing fracture risk in accidental conditions and requiring strict monitoring. Accurate neutron fluence estimations are essential to predict the RPV's lifespan and ensure safety for extensions of the reactor's operational lifetime.

The internship will focus on estimating the uncertainties associated to the vessel fluence calculations, which is based on computer expensive simulations of a nuclear reactor. This estimation is quite challenging, mainly because of the numerous sources of uncertainty associated with the simulations input parameters, among which nuclear data are the main contributors. A PhD student is currently working on this topic and will be the main supervisor of the internship. The outcome of the internship is expected to directly contribute to this research project.

A first calculation aims at evaluating the neutron distribution within the core, during normal operation. This calculation establishes the neutron source term, which is used in a second simulation which propagates these neutrons up to the reactor vessel. The internship will be focused on the uncertainties due to the first step, using deterministic codes (CASMO/SIMULATE) for the core calculation but also the Monte-Carlo code MCNP for the vessel fluence simulation. By sampling the perturbed input data (nuclear data) and performing a sensitivity analysis of the simulation results, will allow the intern to quantify the vessel fluence uncertainty due to the source term and to identify the main contributors. The outcome of this internship will improve the accuracy of vessel neutron fluence evaluation and deepen our understanding of uncertainties arising from nuclear data.

This project will provide the student with the opportunity to gain firsthand experience in using deterministic codes as well as a Monte-Carlo code. It will also allow the student to develop skills in sensitivity analysis and uncertainty quantification. Additionally, the student will have the chance to collaborate closely with experts of different fields and gain firsthand insight into research at one of France's leading nuclear research institutions.

Master's degree, preferably in nuclear engineering. Fluency in English is required, a prior knowledge of the Python programming language would be appreciated.

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Par conséquent, nous accordons la même considération à toutes les candidatures, sans discrimination, pour inclure tous les talents.

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