Thermal degradation studies of paint used in Indian nuclear containment building

Paint is the major source of volatile organic compounds inside a nuclear containment building and consequently a significant contributor towards formation of organic iodides (RI) under nuclear accident conditions. The various chemical compounds present in the paint and their degradation products will determine the speciation of the organic iodides thus formed. In this work, we have investigated the thermal degradation of paint by thermogravimetry (TG) followed by recording the real time mass spectra of the evolved gases using coupled quadrupole mass spectrometer (MS). The paint applied inside Indian nuclear reactor containment building is used in these studies. From the TFA on MS, under N₂, four major compounds, CO₂, butanol, phenol and methyl isobutyl ketone (MIBK) have been identified, among which CO₂ is seen to evolve continuously even upto 800°C which also reflects in TGA plot. Phenol might be a constituent of the paint solvent whereas the others might be the degradation products. On the contrary, in the air, CO₂ evolution ceases at 550°C which supports the observation from the TGA curve. Along with the four compounds, isopropanol is also identified during paint pyrolysis in air; this might be one of the oxidation products