Nuclear Science User Facilities 60 Microstructural and Nanomechanical Characterization of a Lanthana-Bearing Nanostructured Ferritic Steel Irradiated with High Dose Iron Ions Indrajit Charit – University of Idaho – Advanced reactors need high performance materials to serve under harsh service conditions such as higher temperature, higher radiation doses, and extremely corro- sive environment. Nanostructured ferritic steels (NFS) are such a class of materials, produced via mechanical alloying (MA) of the elemental (or pre-alloyed) metallic powder, typi- cally incorporating nanosized yttria powder, followed by a traditional consolidation process such as hot extrusion or hot isostatic pressing (HIP).They are potential materials for advanced fuel cladding and structural materials applications.The perfor- mance of NFS is largely determined by ultra-high-number density of nano-sized oxide particles, which are dispersed throughout the microstruc- ture and stable at high temperatures.A new NFS, known as 14LMT (Fe-14Cr- 1Ti-0.3Mo-0.5La2O3, wt.%), was recently developed by the principal investigator’s group and his project collaborators.The 14LMT alloy uses lanthana in place of traditionally used Y2 O3 . Spark plasma sintering (SPS) was used to consolidate the mechani- cally alloyed powder. Project Description The project was geared toward investigating 14LMT samples exposed to higher self-ion irradiation doses (up to 400 dpa) and understanding the effects of radiation damage doses. No irradiation task was included in the scope of this RapidTurnaround Experiment (RTE) project because the ion irradiation work has already been performed at theTexas A&M Ion Beam Laboratory led by Professor Lin Shao.The ion irradiation parameters used are summarized as follows. Ion type: Fe2+ ion; ion energy: 4 MeV; irradiation mode: defocused; dose: 100, 200, 300, and 400 dpa; dose rate: around 10−4 dpa/ second; irradiation temperatures: 748 K. Furthermore, the initial microstructure of the 14LMT alloy has been thoroughly characterized by transmission electron microscopy (TEM) and atom probe tomography (APT) in CAES MaCS. For the post-irradiation examination portion of the project, four samples, each irradiated at 748 K, were exam- ined.The irradiated specimens are studied for microstructural characteris- tics and mechanical properties. Task 1. Preparation ofAPT andTEM specimens by focused ion beam (FIB) at MaCS. Development of the new 14LMT alloy with excellent radiation resistant property may pave the way for using high performance fuel cladding and structural materials for advanced nuclear reactors.