Low Activation-Modified High Manganese-Nitrogen Austenitic Stainless Steel for Fast Reactor Pressure Vessel Cladding

Low and free nickel austenitic stainless steel alloys were developed successfully and proposed to be used as a liquid sodium coolant fast reactor pressure vessel cladding. A standard austenitic stainless steel SS316L (AISI 316L) was produced as a reference sample. The nickel content was partially or totally replaced by manganese and nitrogen. The microstructure of the produced stainless steel alloys was investigated using Schaeffler diagram, optical microscopy and X-ray diffraction patterns (XRD). Mechanical properties of the developed stainless steel grads were investigated using Vickers hardness, impact and tensile tests at room temperature. Sodium chloride was used to study the corrosion rate of the investigated alloys by open circuit potential technique. Slow and total slow neutrons removal cross sections were measured using 241 Am-Be neutron source and highly calibrated He-3 detector. Eight gamma ray lines which emitted from 60 Co and 232 Th radioactive sources and HPGe detector were used to study the attenuation parameters of the produced alloys. Metallography, Schaeffler diagram and XRD results showed that all the produced stainless steels are mainly of austenite phase with a small ferrite phase. The developed manganese-nitrogen stainless steels showed higher hardness, yield and ultimate tensile strength than SS316L. The elongation of developed stainless steels is relatively lower than the standard SS316L. The impact toughness was reduced with replacement of Ni by Mn. The developed manganese stainless steels have a higher total slow removal cross section than SS316L. On the other hand, the slow neutron and gamma rays have nearly the same behavior for all studied stainless steels.