Loss of coolant accident (LOCA) in pressurized water reactors (PWR) leads to fast transient phenomena, such as the propagation of rarefaction waves within the reactor's internal structures. These waves generate transient pressure loads between different areas, such as the reactor core and the bypass zone, which places stress on the baffle. The deformation of this critical structure can compromise the structural integrity of the reactor and complicate the handling of fuel assemblies, particularly their removal after the accident.

The main scientific objective is to develop, implement, and validate new numerical models that allow for a more accurate simulation of rarefaction wave propagation through complex obstacles. The current state of the art relies on simplified models, validated only for simple configurations such as single-orifice plates. However, there is a need to extend these models to more complex geometries, such as plates with multiple holes, using different numerical methods.
The development of a porosity model to represent fuel assemblies is also crucial. The expected results will be validated experimentally and have direct applications for industrial partners EDF and Framatome, enhancing the industrial relevance of this research.

The thesis will adopt a combined approach, both experimental and numerical. The use of the MADMAX platform will allow for the testing of various complex obstacles and the collection of detailed experimental data using specialized sensors. This data will be used to validate the numerical models developed in the EUROPLEXUS software. Additionally, the simulations will include innovative approaches such as a new porosity model for the internal structures of the reactors. Participation in international conferences and publication of results are planned to ensure the scientific dissemination of the findings.

The thesis will be conducted at the DYN laboratory of CEA Paris-Saclay, equipped with unique experimental facilities, such as the MADMAX platform, and has strong expertise in numerical modeling. Several industrial (EDF, Framatome) and academic collaborations will provide a rich environment for the doctoral candidate, with regular exchanges within international networks.

The ideal candidate should possess solid skills in fluid mechanics, structural dynamics, numerical modeling (finite element, finite volume), and programming. Previous experience with tools like EUROPLEXUS will be a plus. An M2 internship may be offered to familiarize the candidate with the methods and tools used in this thesis.

This thesis will enable the doctoral candidate to acquire highly specialized skills in fluid-structure interactions, numerical modeling, and experimentation in an industrial context. These skills are in high demand in the energy, aerospace, and advanced simulation technology sectors, paving the way for careers in applied research or engineering within the industry.