| Abstract Scope |
Advanced sodium fast reactors necessitate structural materials capable of maintaining mechanical integrity and corrosion resistance in chemically aggressive and thermally demanding environments of high temperature liquid sodium (Na) coolant. While legacy materials such as austenitic (316H, D9) and ferritic-martensitic (T91, HT9) alloys have demonstrated acceptable performance in previous Na-cooled reactor programs, their long-term mechanical and corrosion stability significantly deteriorates above 600 °C. This limitation has prompted the development of next-generation structural materials suited for elevated operating temperatures (≥650 °C). In this study, newly developed nanostructured alumina-forming austenitic (AFA) alloys were evaluated for their compatibility with static, commercially sourced liquid sodium at 700 °C for 1,000 hours. To assess the influence of oxygen impurities and the effectiveness of protective alumina scales, specimens were exposed both with and without pre-oxidation treatment. Room-temperature tensile specimens were used to evaluate the effect of sodium exposure on mechanical performance. Post-exposure characterization, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and compositional analysis, was conducted to examine corrosion scale formation, elemental redistribution, and substrate microstructural integrity. The results will provide insight into the role of surface oxide layers in mitigating corrosion and mass transfer, as well as the degradation in tensile properties resulting from high-temperature sodium exposure. |