Molten-salt reactors are the subject of significant research at the national and international levels, particularly to assess their potential for actinide and nuclear waste management. In this context, the knowledge of corresponding salt properties and their evolution as a function of temperature and composition is crucial. This includes melting point, viscosity, surface tension, density and thermal conductivity quantification in the temperature range of 600-800°C, that require specific and complex experiments for their determination. To overcome the current limitations of measurement techniques and gain new insight into these critical properties we propose to develop an original set of experiments and methodologies relying on laser and optical techniques. Specifically, high power lasers will be used to drive the “salts” at high temperature, and imaging, spectrometry, thermography and pyrometric techniques will be deployed to determine the properties of interest thanks to the great flexibility offered with these optical and laser-based techniques. The proposed approach to reach the objectives goes from the conceptual designs tested in a photonics laboratory to the application in a hot cell laboratory, which is the final targeted point, thanks to a coupled modelling approach [see for example: 1, 2, 3].

The thesis work will be conducted in collaboration between the Fresnel Institute in Marseille and the Institute for Research on Nuclear Systems for Low-Carbon Energy Production (IRESNE) at CEA/Cadarache centre.
The thesis will enable the student to acquire skills in optical instrumentation, laser heating, high-temperature metrology, image processing, and numerical modelling. These skills can be applied in public or industrial research, particularly in the fields of instrumentation, materials, and nuclear energy.
Thesis supervisor (CEA): Y. Pontillon

Reference.
[1] Gabriel Aulanier, Matthieu Reymond, Thomas Doualle, Cihan Koc, Julien Lumeau, Yves Pontillon, Laurent Gallais, Development of a spectral ellipsometer for the investigation of the optical properties of mono- and polycrystalline UO2, Optics Continuum, vol. 5, 2647-2665, 2026
[2] Matthieu Reymonda,b, Thomas Douallea,b, Jerome Sercombea, Mathilde Roccaa, Mehdi Nasselahsena, Christian Colina, Yves Pontillona and Laurent Gallaisb, High power laser heating of nuclear ceramics for the generation of controlled spatio-temporal gradients, J. Appl. Phys. 134, 033101 (2023)
[3] T. Doualle, V. Le Guillous, V. Klosek, C. Onofri-Marroncle, M. Reymond, L. Gallais, Y. Pontillon, ‘Development of UO2 thermal diffusivity measurement with laser techniques’, EPJ Web of Conferences 253, 07005 (2021)