Application of evolved gas analysis to cold-cap reactions of melter feeds for nuclear waste vitrification

• We applied the TGA-GC–MS combination to perform EGA of glass batches.
• We confirmed the proportionality between mass loss rate and gas evolution intensities.
• Proportionality coefficients can be obtained via single-reaction calibration.
• Quantitative EGA allows mass loss rates to be matched with evolution rates for gases.
• Industrial and waste glass technology can benefit from quantitative EGA.

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. We employed the thermogravimetry-gas chromatography–mass spectrometry (TGA-GC–MS) combination to perform evolved gas analysis (EGA). Along with identifying the gases evolved, we performed quantitative analysis relating the weighted sum of intensities of individual gases in linear proportion with the differential thermogravimetry. The proportionality coefficients were obtained by three methods based on the stoichiometry, least squares, and calibration. The linearity was shown to be a good first-order approximation, in spite of the complicated overlapping reactions.