Development of oxidation resistant iron alloys for LWR cladding

An effort is underway to develop optimized oxidation resistant iron alloys for use as LWR fuel cladding. The ferritic alloys are that of Fe-Cr-Al category that given an appropriate composition offer significantly reduced oxidation kinetics (up to three orders of magnitude) in high-temperature steam environments when compared to zirconium alloys. Optimization of chromium and aluminum content is necessary to balance the high-temperature (>1000°C) steam oxidation behavior with irradiation embrittlement and fabricability. At the same time it is necessary for the alloys to exhibit adequate resistance to uniform corrosion and stress corrosion cracking in high-temperature water (∼320°C) across the various PWR and BWR water chemistries and service conditions. The effects of minor alloying elements can be essential in achieving an optimized composition that offers corrosion and oxidation resistance while offering adequate mechanical properties. The comprehensive set of activities focused on optimized alloy development consist of cast production and subsequent thermomechanical treatment (TMT), demonstration of tube production and welding, high-temperature oxidation tests, high-temperature water corrosion experiments, and finally irradiation testing. The latter will be performed on miniature tensile specimens irradiated in the High Flux Isotope Reactor (HFIR) at ORNL.