Development of nano carbide dispersed advanced radiation resistant austenitic stainless steels (NC-ARES) for reactor internals

Abstract

Austenitic stainless steels (SSs) are widely used as in-core materials in current nuclear systems, with combination of good corrosion resistance, ductility, and mechanical properties. Meanwhile, they subjected to high neutron fluence of typically up to 70‒100 displacement per atom during operating time period of more than 40 years. However, the neutron irradiation causes deleterious effect on the microstructural evolution which effects on mechanical properties such as irradiation hardening and embrittlement. Especially, austenitic SSs are highly susceptible due to poor void swelling resistance, which would be a life-limiting degradation for reactor internal components. Therefore, development of advanced nuclear reactors with longer lifetime and better efficiency requires advanced materials that can withstand higher irradiation dose. In this thesis, an austenitic SS with uniformly distributed nanosized NbC precipitates, named as ARES-6P, was developed, by controlling chemical composition and thermo-mechanical processing. Then, the strengthening effects of the uniformly distributed nanosized NbC precipitates were evaluated using the micropillar compression test. Finally, the swelling resistance of the newly developed ARES-6P was investigated using the heavy ion irradiation and the results were compared with commercial 316 SS.