Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 76 Page 77 Page 78 Page 79 Page 80 Page 81 Page 82 Page 83 Page 84 Page 85 Page 86 Page 87 Page 88 Page 89 Page 90 Page 91 Page 92 Page 93 Page 94 Page 95 Page 96 Page 97 Page 98 Page 99 Page 100 Page 101 Page 102 Page 103 Page 104 Page 105 Page 106 Page 107 Page 108 Page 109 Page 110 Page 111 Page 112 Page 113 Page 114 Page 115 Page 116 Page 117 Page 118 Page 119 Page 120 Page 121 Page 122 Page 123 Page 124Nuclear Science User Facilities 74 Irradiation Effects in Oxide Nanoparticle Stability and Matrix Microstructure in ODS Steel Neutron Irradiated to 3 dpa at 500°C Kumar Sridharan – University of Wisconsin, Madison – kumar@engr.wisc.edu One of the major steps toward the implementation of Generation IV nuclear reactor systems is the development of appropriate materials for cladding and other core internal components that will be able to withstand high doses and temperatures. Oxide dispersion strengthened (ODS) steels are deemed as being among the promising candi- date materials for cladding and core internals for advanced nuclear reactors, by virtue of their superior mechanical properties at high temperatures.These properties arise from a fine dispersion ofY-Ti oxide nanoparticles in the steel matrix, which serve as pinning points for dislocation motion and point defect annihilation sites.Additionally, these oxide nanoclusters are expected to trap transmutation-produced helium in small, high-pressure bubbles.To apply these materials in the extreme envi- ronments of next generation nuclear reactors, a complete understanding of their radiation response is necessary. Project Description In the proposed research, a 9%Cr ODS steel in unirradiated and irradiated (with neutron to 3 dpa at 500°C) conditions, were analyzed with high- resolution microscopy techniques for microstructural and microchemical changes induced by neutron irradiation. The analysis was performed utilizing Transmission Electron Microscopy (TEM), Scanning-TEM coupled with Energy Dispersive Spectroscopy (EDS), and Local ElectrodeAtom Probe (LEAP, also known as atomic probe tomog- raphy, [APT]). Many studies in literature have investigated the stability of theY-Ti oxide nanoclusters in ODS steels using proton and heavy ion irradiations, but there have been relatively few studies the effects of neutron radiation on these oxide nanoclusters. Specifically, this research focused on the changes caused by the neutron irradiation on the size, density, and composition of the nanoclusters as well as on the forma- tion of extended defects (dislocation ODS steels are deemed to be among the most promising candidate materials for cladding and core internals of next generation nuclear reactors. Figure 1. LEAP images showing elemental distribution maps at near- atomic level for the as- received (top row) and neutron irradiated (bottom row) ODS steels.