Combining Thermogravimetry-Mass Spectrometry and Target Factor Analysis for Rapid Characterization of Volatiles from...

Thermogravimetry coupled with simultaneous evolved gas analysis by mass spectrometry was used for discerning organic compounds released during the thermal degradation of paint whose chemical compositions are not readily accessible. Thermogravimetric analyses up to 600°C revealed distinct degradation patterns under inert and oxidative conditions. Significant degradation of paint initiates at around 360°C and concludes at 500°C in a nitrogen atmosphere. However, under oxidative conditions, degradation began at 100°C, with notable mass loss extending from 300 to 600°C, with a distinct event at 500°C. Moreover, the overall mass loss in air has been observed to be 3% higher than that in nitrogen. The rapid characterization of the volatiles was made possible by model-free target factor analyses of evolved gas mass spectra. The temperature-correlated mass analyses revealed potential volatile sources, including structural breakdown and oxidative conversion. Comparative analyses revealed predominantly oxidative conversion of organics to CO₂ during degradation in air. The evolution of several classes of organics during the thermal degradation of paint is a matter of great concern for postulated accident scenarios in nuclear power plants. The low molecular weight organic volatiles may be taken up by iodine aerosols released into the containment during an accident, potentially forming organic iodides, which are biological hazards. Thus, identifying these volatile organics is crucial for accurately estimating the source term of volatile organic iodine.