In France, high-level nuclear waste is vitrified. The components of the waste are integrated in a homogeneous vitreous matrix. However, platinum group metals (PGM) Pd, Rh and Ru are very poorly soluble in the glass melt and they form particles, combined or not with oxygen or tellurium.
Ru and Rh may reduce in their metallic state during glass processing. They are then more electrically conductive and their effect on the physical properties of the glass melt may affect the vitrification process control. Hence, the knowledge of the speciation and the morphology of the PGM elements is essential for the control of the process.
Thereby, this PhD will be split in 2 interdependent approaches: the first one by thermodynamic Calphad calculations and the other one by experimentations. First, the experimental approache will aim to understand and quantify the reduction of (Ru,Rh)O2 and the solubilisation of Ru and Rh in Pd-Te thanks to elaborations and characterizations (SEM and XRD mainly) of glasses with PGM particles. The results will complete a Calphad database. Calculations will help to discuss experimental results and will enable to predict the PGM state in the glass melt during the industrial vitrification. Secondly, electrical conductivity measurements at high temperature will be implemented on the glasses previously made to determine the impact of Ru and Rh speciation on the global conductivity of the melt.
The applicants must be rigorous, autonomous and have good communication and writing skills. Knowledge and experience in the field of glass or thermodynamics would be a plus.