Thermodynamic Modelling of the Pd-Te-Ru System for Nuclear Waste Glasses Application

Abstract

AbstractThe waste management process of the French nuclear spent fuels is managed by a new vitrification conditioning step. High level radioactive borosilicate glasses are melted by induction in a cold crucible to accommodate a wide range of minor actinides and fission products. Among the fission products, platinoids precipitate in the form of (Pd-Te, Ru-Rh, Ru) metallic particles in the glass. The microstructure of these phases can affect the physicochemical properties of the melt during the vitrification process. To predict the thermodynamic properties of these alloys in the glass, a database is being developed on the Pd-Rh-Ru-Te system using the Calphad method. The binary (Pd-Te, Pd-Ru, Ru-Te) and ternary (Pd-Te-Ru) systems have been modelled. The Pd-Te-Ru ternary system built by extrapolation from the binaries enables to calculate ternary isothermal sections and thermodynamic properties of the platinoid phases between 873 K and 1573 K. Solidification paths are also calculated for Pd-Te alloys representative for those observed in the glasses. The phase composition at equilibrium and the Ru solubility limit in Pd-Te alloys are also calculated.