The nuclear fuel performances depend on their thermomecanical behaviors and, therefore, their thermal conductivity. This property varies significantly with high porsity levels especially in mixed oxided (composed of uranium and plutonium) used in fast ractors.

The aim of this thesis is to assess the impact of the pore qualities and shapes on the thermal conductivity on fissile materials and to propose a thermal conductivity law depending of the quantity, the length, the shape and the interconnectivity of its porosity. To reach this goal, recent measures on thermal properties are in progress by laser heating, allowing a better understanding of the fuel behavior in temperature ranges mostly unexplored like very high temperatures (until 2500°C), are in progress in the european research center (JRC) in Karlsruhe. These measures are performed on materials with different microstructures. These measures will be interpreted from thermograms and compared to simulation results (image analysis, converting 2D image in a 3D problem, TM-FFT)[1].
This thesis will take place in the French Institute for Research on Nuclear Systems for Low-Carbon Energy production (IRESNE) in the Expertise and Validation on multi-fuel Applications Laboratory (LEVA). LEVA is part of the Fuel Study and Simulation Department and its missions consist of :
- Answer to industrial demands by providing studies ;
- Validation of the Scientific Calculation Tools (OCS) of the PLEIADES plateform ;
- Enhance the fuel behavior understanding ;
- Manage the Fuel databases.
Finally, the collaboration with JRC Karlsuhe will be a chance to work within an international framework which also is a strenght of LEVA.

This work will be valorized through conferences participations and publications in peer-reviewed journals. Furthermore, the PhD student will have the possibility to acquire or strengthen some technical skills (experimental data interpretation, modelling) applicable in various fields of material science and engineering.

[1] This work forms a natural extension of the PHD thesis 'The Thermal conductivity of mixed oxide fuel (MOX) : effect of temperature, elementary chemical composition, microstructure and burn-up in reactor' - TEL - Thèses en ligne.