With the energy transition and the paramount importance of the nuclear energy in this context, it is pivotal to understand the consequences of potential accident with core meltdown, as well as thinking about mitigation strategy.
During a nuclear severe accident with core meltdown a magma called corium can form a pool in the reactor lower head. The pool is not homogeneous and can stratify into multiple immiscible layers. The composition of the pool may evolve in time, due to progressive material assimilation. With the evolution of the global composition of the corium, the properties of the layers evolve. The vertical position of these layer may then change. This change comes with the creation of droplets from a layer which then cross the other one. The vertical order of the different layers as well as their movements have a significant impact on the heat fluxes imposed on the reactor vessel. A better understanding of these phenomena improves safety of both nowadays and future nuclear reactors.
Modelling work has been done, but it lacks validation and need calibration. Prototypical experiments (with actual materials present inside a reactor) are difficult to carry and are not foreseen in the near future. This PhD aims at experimentally studying the mass transfer between a droplet and its surrounding as well as the droplet creation. The planned experimental setup will use a water-based system which allow for local measurement. The goal is to validate, calibrate the existing model, and potentially create new ones. The final goal being to capitalize the work into PROCOR software platform. The experimental setup will be constructed and operated in LEMTA laboratory in University of Lorraine, where the student will work.
The PhD work will be mainly experimental but will also require software use for calibration, validation and for the design of the experimental setup. This work will be conducted in close collaboration between the laboratories LMAG in CEA/IRESNE (Cadarache) and LEMTA in University of Lorraine (Nancy). The student will work in LEMTA, where the experiments will be conducted, while being part of the CEA. The student will benefit from LEMTA’s expertise in building of experimental setup, transport phenomena in fluids and metrology, and from LMAG’s expertise in mass transfer, physical modeling and simulation in the scope of nuclear severe accidents. The student will regularly interact with CEA team which will follow the work closely. The student will therefore have to regularly go to CEA Cadarache.
The PhD student will be integrated to a dynamic environment comprised of researchers and other PhD students. The PhD candidate needs to be knowledgeable in transport phenomena, and needs to have a taste for experimental sciences.