Impact of corrosion on the emissivity of advanced reactor structural alloys

Under standard operating conditions, the emissivity of structural alloys used for various components of nuclear reactors may evolve, affecting the heat transfer of the systems. In this study, mid-infrared emissivities of several reactor structural alloys were measured before and after exposure to environments relevant to next-generation reactors. We evaluated nickel-based alloys Haynes 230 and Inconel 617 exposed to helium gas at 1000 °C, nickel-based Hastelloy N and iron-based 316 stainless steel exposed to molten salts at 750-850 °C, 316 stainless steel exposed to liquid sodium at 650 °C, and 316 stainless steel and Haynes 230 exposed to supercritical CO2 at 650 °C. Emissivity was measured via emissive and reflective techniques using a Fourier transform infrared (FTIR) spectrometer. Large increases in emissivity are observed for alloys exposed to oxidizing environments, while only minor differences were observed in other exposure conditions.