Nuclear energy is one of the pillars of the energy transition due to its low carbon footprint. It requires advanced safety studies, particularly regarding hypothetical severe nuclear accidents. These scenarios involve core meltdown and the formation of corium (molten radioactive material magma). Understanding corium behavior is a key element of nuclear safety.
At IRESNE institute of CEA Cadarache, the MERELAVA facility studies accident mitigation strategies by spraying water onto corium from above. A prototypical corium bath (containing depleted uranium) is cooled by water spraying under realistic conditions. This setup allows the study of complex interactions between corium, water, and the sacrificial concrete beneath.
In this context, the water ingression phenomenon plays a central role in corium cooling. During spraying, the solidified crust cracks, water seeps into the cracks and evaporates, significantly increasing the extracted heat flux compared to conduction alone. However, current models poorly describe this mechanism and struggle to predict its impact, mainly due to its highly multi-physical nature.
This thesis aims to study ingression through dedicated experiments on MERELAVA, to characterize the crust and to measure the ingression flux using 3D-printed representative matrices. The goal is to improve the existing physical model, with results compared to more complex experimental data. The thesis will primarily take place in the Severe Accidents experimental laboratory of the IRESNE institute. The candidate should have expertise in fluid mechanics and heat and mass transfer.