2016 | ANNUAL REPORT 91 a migration towards sinks.At the same time, vacancies are inclined to diffuse to voids and promote the growth of voids at intermediate temperatures. The impact of carbon addition on the accumulation of defect clusters and solute redistribution in Fe‑9Cr alloys during ion irradiation is not clear. This research provided fundamental knowledge on the materials degradation of materials in reactor environments and sheds light on the design of microstructure in radiation resistant materials for advanced nuclear reactors of many types, including light water cooled reactors. Figure 2. Atom probe tomography of tempered martensite in as- received Fe-9Cr alloy. Enrichment of carbon and titanium in the grain boundary were obtained. Accomplishments We have prepared Fe-9Cr with 0.02wt.% C samples for irradiation studies. High temperature and high dose irradiation experiments were performed in the Michigan Ion Beam Laboratory at the University of Michigan. By using electron back- scatter diffraction (EBSD), we identi- fied two phases in the matrix: they are δ-ferrite and tempered martensite. Atom probe tomography at the Center for Advanced Energy Studies (CAES) was used to measure the differences in chemistry in both phases.The focused ion beam at the CAES was utilized to make samples for atom probe tomography (APT) analysis andTEM characterization.The results A fundamental understanding of the effects of carbon on the solute redistribution in these alloys will help us design the chemical composition of Fe-Cr based alloys with improved radiation performance in nuclear reactors.