Impact of corrosion on the emissivity of advanced-reactor structural alloys

TL;DR

This study measures how the emissivity of various nuclear reactor alloys changes after exposure to different environments, revealing significant increases in oxidizing conditions which impact heat transfer.

Contribution

It provides the first comprehensive comparison of emissivity evolution in multiple alloys under relevant reactor environments.

Findings

Oxidizing environments cause large emissivity increases.

Minor emissivity changes occur in non-oxidizing conditions.

Emissivity measurements were performed using FTIR spectroscopy.

Abstract

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 $^{\circ}$C, nickel-based Hastelloy N and iron-based 316 stainless steel exposed to molten salts at 750-850 $^{\circ}$C, 316 stainless steel exposed to liquid sodium at 650 $^{\circ}$C, and 316 stainless steel and Haynes 230 exposed to supercritical CO2 at 650 $^{\circ}$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.