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Nuclear Science User Facilities 80 Irradiation Effects in Aged Cast Duplex Stainless Steels YongYang University of Florida yongyangufl.edu By correlating microstructural studies with associated mechan- ical tests this research provides a fundamental understanding of the aging behavior of cast stainless steels during the 40 years of as-designed reactor life and more importantly during the 60 years and beyond of a reactors anticipated extended life. Project Description Researchers used transmission electron microscopy TEM and atom probe tomography APT to systemically characterize the neutron-irradiated cast stainless steels under non-aged and aged conditions focusing on precipita- tions and elemental segregation.The results of the study will provide some of the first knowledge of the synergistic effects of thermal aging and neutron irradiation on microstructural evolu- tion in reactor components made of cast stainless steel. Accomplishments Microstructural changes in the ferrite atoms of thermally aged only neutron- irradiated only and neutron-irradiated after thermal aging cast austenitic stainless steels CASS were investigated using APT. It was found that low-dose neutron irradiation could effectively induce spinodal decomposition in the ferrite atoms of non-aged CASS while the neutron irradiation of aged CASS would further enhance the spinodal decomposition Figure 1. Determining the combined effects of thermal aging and low-dose neutron irradiation on duplex stainless steels cast stainless and austenitic stainless steel welds is going to have major implications for the sustainability of light water reactors LWR when their service lives are extended to 80 years. Figure 1. Spinodal decomposition of ferrite phase in cast stainless steels where the red color represents Fe atoms and the blue color is the background. Aged As-cast Aged IrradiatedAs-cast Irradiated