Investigation of Thermal Stability of Fluoroelastomer in Simulated Severe Accident Environment of Nuclear Power Plants

To ensure the survivability and functionality of safety-related equipment, the assessment of polymeric materials must be performed. Therefore, to investigation of degradation of polymeric materials is very important to ensure the safety of NPP. In this study, behavior of thermal stability of fluoroelastomer in normal operation condition and SA environment (heat, radiation) were investigated. Fluoroelastomer specimens are exposed to normal operation condition. Irradiation test and accelerated thermal aging were performed sequentially. And degradation test in irradiation test and SA temperature profile were conducted. To investigate the thermal stability behavior by thermogravimetric analysis (TGA) and the Fourier transformed infrared (FT-IR) spectroscopy was performed to investigate the change of molecular structure. Degradation tests under simulated normal operation condition and SA environment were performed to investigate the thermal stability behavior of fluoroelastomer. This degradation behavior is caused by the decreasing of the crystalline region due to the scission of molecular bonds and reaction with oxygen in the air during C=O formation process. After the accelerated thermal aging and thermal degradation on irradiated fluoroelastomer, decreased thermal stability due to the irradiation was restored. When heat is applied to the groin where the crystalline region is reduced due to oxidative degradation, the tie molecular is reformed and recrystallization is generated.