Characterization and modeling of chemical reactions taking place during the vitrification of high level nuclear waste

Abstract

Several chemical reactions take place during the vitrification of high-level nuclear waste. The integration of these chemical aspects in process numerical simulation tools is one of the key points in the approach of improving the prediction capabilities of numerical tools today. In this study, based on simultaneous differential scanning calorimetry-thermogravimetry (DSC-TGA) and the run/rerun method, we propose a modeling of the kinetics of chemical reactions taking place when nuclear glass precursors are subjected to constant heating. For the mathematical modeling, a weighted sum of nth order reactions was used to describe the overall mechanism. A hybrid approach coupling the Kissinger and least squares methods was performed to identify the apparent kinetic parameters. Along with the thermal characterization, we also provide some information about the nature of the main reactions through microstructural evolution and evolved gas analyses.