Lead fast reactor (LFR) and lead-bismuth eutectic fast reactor (LBEFR) are best performing in terms of power density and economics. For decades, the issues of corrosion and how it will change with irradiation have been the bottleneck in development. My project focused on the simultaneous irradiation and corrosion of candidate steels (T91, HT9) and some FeCrSi model alloys in LFR/LBEFR. I analysis samples with atom probe tomography (APT) accompanied by FIB, EDS, EBSD, and TKD to investigate the elements segregation caused by corrosion and irradiation, the influence of grain type and grain boundary, and newly formed structures like clusters, voids, and loops. With all the information above and the TEM, Chemi-STEM, and HR-EBSD/TKD data from our collaborators, we will try to figure out the mechanisms of corrosion and irradiation in LFR and LBEFR.