The production of electricity through nuclear energy is a key pillar of the energy transition due to its low carbon footprint. In a continuous effort to improve safety and performance, the development of new knowledge and tools is essential.

Fuel assemblies, which are components of a reactor core, face various challenges involving thermo-hydraulic phenomena. These include flow-induced vibrations, power transmission associated with critical fluxes, and fluid-structure interactions in cases of assembly deformation or seismic excitation. In all these situations, the behavior of the fluid near the wall plays a crucial role. The use of Computational Fluid Dynamics (CFD) allows for the simulation of these phenomena with the goal of obtaining predictive tools. The experimental validation needs required by today's simulations push classical measurement techniques to their limits. There is a strong need for refined experimental data in both time and space on complex geometries.

This doctoral project aims to address this need by leveraging the latest advancements in optical measurements for turbulent flows. By combining index matching techniques, panoramic cameras, and Particle Tracking Velocimetry (PTV), it is possible to measure the velocity field in a representative volume (approximately 1 cm³) with a spatial density of around 10 micrometers. This allows for the simultaneous measurement of flow in the boundary layer and the hydraulic channel.

The thesis will primarily be conducted at the Hydromechanics Laboratory (LETH) at the IRESNE Institute (CEA Cadarache) and will involve collaboration with the Thermo-Fluids Lab at George Washington University. Travel to the USA will be required.