The ternary system palladium–rhodium–tellurium: A Study to understand phase formation in the vitrification process of high-level waste concentrates (HLWC)

Abstract We present the results of our investigation on the thermodynamics of the ternary system Pd–Rh–Te at temperatures of 1150, 1100, 1050, 1000, 950, 900, and 750 °C under inert conditions. The goal of these comprehensive studies was to determine the phase stability fields of the phases in the Pd–Rh–Te system under the aspects of vitrifying high-level waste concentrates from reprocessed spent nuclear fuels. Electron-probe microanalysis (EPMA), X-ray diffraction (XRD), and differential thermal analysis (DSC/TGA) were applied to quantify elemental phase composition, phase content and thermophysical properties. In the temperature range from 1150 to 1000 °C, the Pd–Rh–Te system (0–50 at.% tellurium) is dominated by the extensive three-phase space α 1 + α 2 + L, where α 1 , α 2 denote the solid solution phases Rh(Pd,Te) and Pd(Rh,Te), respectively, and L (Liquid) denotes a tellurium-rich melt phase. This three-phase stability field describes the phase equilibrium conditions relevant for the process conditions to vitrify high-level waste concentrates from reprocessed spent oxide fuels.