PNNL

Abstract

In the vitrification of nuclear wastes, the melter feed (a mixture of nuclear waste and glass forming and modifying additives) experiences multiple gas-evolving reactions in an electrical glass-melting furnace. Foams from the residual gases can significantly alter the melting rate through mass and heat transfers. We employed the thermogravimetry-gas chromatography-mass spectrometry (TGA-GC-MS) combination to perform quantitative evolved gas analysis (EGA) and developed a simple calibration model which correlates the overall mass loss rate with the evolution rates for individual gases. The model parameters are obtained from the least squares analysis, assuming that the gas-evolving reactions are independent. Thus, the EGA adds the ‘chemical identity’ to the reactions indicated by the ‘phenomenological’ kinetic model.