In the context of the energy transition and the place of nuclear power in the energy mix, controlling safety and optimizing reactor performance represent imperative research areas with high added value. In this context, boiling at high pressure and temperature is a key issue for water reactors widely deployed in France and around the world.
The many works on this subject carried out in the past show their limitation in terms of representativeness and present certain gaps (e.g. the evolution of the topology of the flow at high pressure). The proposed subject therefore concerns the characterization of nucleate boiling for a wide range of pressure and temperature conditions, and more particularly the study of the coupling between the thermal properties of the wall and the flow (bubble sizes, detachment frequency, local void ratio, etc.). This work will also provide data relating to boiling models that can be used in CFD-type numerical calculation tools. Direct visualization of the flow using portholes (a process successfully implemented in the past), coupled with the use of stereological tools (in collaboration with the LRVE at CEA Marcoule) and associated with a measurement of the wall temperature, should make it possible to achieve the set objectives. These measurements carried out under representative reactor conditions (thermohydraulic conditions, real fluid, representative heating surface) make this study original compared to existing work.
After an initial critical literature review, the PhD student will design and test the experimental devices before implementing them through test campaigns on a dedicated installation. The results collected will be analyzed, interpreted, compared with existing models and may, if necessary, lead to the construction of new models. This thesis will take place on the POSEIDON experimental platform, dedicated to flows studies, and will allow the doctoral student to approach all phases of a research project, from the design of experimental devices to the interpretation of the results obtained.