Nuclear Science User Facilities 92 indicate that carbon concentration in tempered martensite is lower than that in δ-ferrite phase andTEM micro- graphs of irradiated samples suggest that tempered martensite exhibits a stronger swelling resistance.This might be attributed to the lowered carbon concentration in tempered martensite and/or sink effects of lath boundaries. In addition, we performed in-situ irradiation experiments at the IntermediateVoltage Electron Micros- copy (IVEM) Facility at Argonne National Laboratory to understand the influence of carbon addition on the growth kinetics of dislocation loops at 300°C.This research provided a comprehensive understanding on how carbon addition affects the solute redistribution of Fe-9Cr alloy under irradiation at different conditions. We would like to acknowledge the following institute and individuals for the contribution. MIBL, University of Michigan, Gary Was. IVEM,Argonne National Laboratory, Mark Kirk. SCK CEN, Belgian Nuclear Research Centre, L. Malerba and M. Konstantinovic. Future Activities A new proposal based on this research has been submitted to NSUF. Publications [1.] C. Sun, et al., “Void swelling of δ-ferrite and tempered martensite in a Fe-9Cr model alloy subjected to 8 MeV Fe ion irradiation,” 2017 Environmental Degradation of Materials in Nuclear Power Systems—Water Reactors Conference, submitted. Figure 3. Bright-field and dark- field TEM micrographs of irradiated δ-ferrite in Fe-9Cr alloy. Irradiation-induced voids were formed in the damaged region.