In the context of the energy transition and the crucial role of nuclear power in a low-carbon energy mix, understanding and then mitigating the consequences of any accident leading to even partial core meltdown is an imperative research direction.
In the event of a severe core meltdown accident, the amalgam of materials produced by core meltdown, or corium, may interact with the concrete of the plant's floor. The lack of understanding of local and interfacial physical phenomena during corium-concrete interaction (ICB) has led to the development of various international simulation tools. None of them has been able to explain the recent observations at the Fukushima Daiichi accident site. It is therefore crucial to improve the ICB simulation tools.
The aim of this thesis is to carry out a detailed, local experimental study of the corium/concrete interface with prototypical corium (depleted uranium). To this end, the candidate will design a test device to be introduced into the VITI inductive furnace of the PLINIUS platform dedicated to the study of severe accidents at the Cadarache center. After qualification of the experimental set-up, local corium/concrete interaction tests in VITI will be carried out on different types of concrete (including a sample from Fukushima) and with different coriums, enabling an incremental approach using separate effects. Ablation will be characterized via mass loss and hydrogen release. The interface will also be characterized after rapid corium removal. Samples will also be X-rayed (e.g. tomography). As the work progresses and the phenomenology of the Molten Corium Concrete Interaction is understood, a model may be developed and integrated into a simulation tool.
The thesis work will be carried out jointly in the experimental and severe accident modeling laboratories of the IRESNE institute at Cadarache, in a research environment of the highest international standard for the study of multiphysical phenomena at very high temperatures. This work will also be enriched by research carried out within the framework of the ANR IMMOC, in partnership with academics (CNRS Laboratoire Navier, AMU-CNRS Madirel...).