In France, the high-level nuclear waste is vitrified. The components of the waste are integrated in a vitreous borosilicate network and form a homogeneous glass. 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.
These PGM particles may modify the physical properties of the glass melt and especially its electrical conductivity wich is paramount for the process control. Hence, the knowledge of the speciation and the morphology of the PGM elements is essential for the control of the vitrification 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-EDS-WDS 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.