Effect of the redox potential on the general corrosion behavior of industrial nuclear alloys

During the last decade, the international nuclear materials community has been investigating a robust fuel version for Light Water Reactors called Accident Tolerant Fuel (ATF). One of the ATF concepts is to replace the current Zr tubing with an iron-chromium-aluminum (FeCrAl) alloy or IronClad. Extensive out-of-pile autoclave testing showed that the dissolution (corrosion) of the FeCrAl alloys in ∼300 °C water is highly dependent on the chemistry of the alloy and on the chemistry of the water. The dissolution rate of FeCrAl and other industrial Cr containing alloys is higher in hydrogen environments than in oxygen environments, since under oxygen conditions they form a more protective surface oxide. Alloys with higher Cr content (e.g., APMT) are more resistant to dissolution than lower Cr alloys. Studies also showed that the presence of a few parts per billion Zn considerably reduced the dissolution rate of FeCrAl.