This proposal is a coordinated set of experiments with post-irradiation examination and analyses that will provide significant new insight into the irradiation performance of ferritic alloys for advanced reactor applications. The main objective of this research effort is to produce a set of irradiation conditions on FeCr alloys, ranging from model alloys to commercial and developmental alloys, which will provide the basis for materials and materials modeling development to assess radiation performance. The effort will develop a new level of understanding of the irradiation performance of this alloy system and serve as a mechanism to develop modeling capabilities to better predict future alloy performance and development.The ATR experiments will extend the current experimental and modeling activities so that irradiation behavior can be directly modeled and compared across a variety of irradiation systems. Experiments will be performed on model Fe and FeCr alloys, on mod 9Cr-1Mo and HT-9 commercial alloys, and on 3Cr-base and MA 957 developmental alloys. ATR experiments will be performed at 300, 450 and 550C to doses ranging from 0.01 displacement per atom (dpa) to 10 dpa.This research proposal is based on a number of ongoing studies within the research team which includes investigators at the University of Illinois, Georgia Tech, North Texas University, LANL, ANL, and General Electric Nuclear. The ongoing studies include modeling of nascent irradiation damage events using molecular dynamics (MD) approaches and kinetic Monte Carlo (kMC) to follow point defect and cluster evolution. It also includes modeling of tensile property evolution using viscoplastic self-consistent (VPSC) polycrystal approach to understand the tensile, and possibly fracture behavior, of model alloys and commercial alloy systems as a function of irradiation dose, which can be further coupled to finite element analysis of deformation and structural loads.The experimental program is based on current irradiation damage and tensile property experiments. The irradiation experiments employ ion beams to induce irradiation damage to several dpa at irradiation temperatures up to 550C. Post irradiation analysis of these specimens is being carried out with transmission electron microscopy (TEM), positron annihilation spectroscopy (PAS), x-ray spectroscopy, atomic force microscopy (AFM) and other techniques. All of these techniques will be employed in the current program.The mechanical properties work employs miniature tensile techniques to follow the irradiation induced hardening properties of these alloys. Unique in our work is the use of the Advanced Photon Source (APS) to follow the tensile deformation stages during tensile loading to help understand flow localization processes. In addition, compact tension (CT) specimens will be used to characterize fracture toughness properties.This research project will accomplish the following: (1) tie together a number of ongoing, related irradiations in the FeCr system, (2) provide a major new basis for materials modeling for irradiation performance ranging from very basic (MD) to very applied levels (VPSC-FEM) and (3) provide a well coordinated set of irradiation performance data which range from model to commercial and developmental alloy systems.