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 124
Page 125
Page 126
Page 127
Page 128
Page 129
Page 130
Page 131
Page 132
Page 133
Page 134
Page 135
Page 136
Page 137
Page 138
Page 139
Page 140
Page 141
Page 142
Page 143
Page 144
Page 145
Page 146
Page 147
Page 148
Page 149
Page 150
Page 151
Page 152
Nuclear Science User Facilities 66 Radiation-Induced SegregationDepletion at Grain Boundaries in Neutron-Irradiated 304SS at Low Dose Rates Emmanuelle Marquis University of Michigan emarqumich.edu Radiation-induced segregation depletion and its deleterious impact on properties in austenitic stainless steels have been studied extensively particularly at high dose rates typically 10-4dpas. However validation of life-extension plans for light water reactors and future applications in advanced fission and fusion reactors require input data on the effects of high fluence obtained at low dose rates on the microstruc- ture and mechanical properties of these steels. Project Description Irradiating the 304 stainless steel 304SS hex-blocks in the Experi- mental Breeder Reactor EBR-II fast reactor to relatively high doses at low dose rates provides an opportunity to investigate the irradiation-induced microstructures.This was performed using transmission electron micros- copy TEM and atom probe tomog- raphy APT both at CAES and at the University of Michigan.The objectives of the work were to Understand the synergy or competi- tion between radiation-induced segregation carbide formation and swelling as function of dose rate dose and temperature. Understand the microstructural changes induced near the sodium- wetted surfaces and their con- sequences on radiation-induced segregation at grain boundaries. Benchmark the APT measurements by comparing them to informa- tion obtained by analytical electron microscopy. Develop a mechanistic under- standing for the observed changes. Accomplishments After a delayed start of over two years due to technical issues regarding materials selection availability and preparation the project progressed significantly thanks to the involvement of Bulent Sencer at INL.The micro- structures of two hex-blocks irradiated at different dose rates and doses were characterized in great detail including voids nickel Ni-silicon Si clusters dislocation loop density loop chem- istry phosphide precipitates grain boundary chemistry grain boundary carbides and surface chemistry. Selected examples of these observa- tions are illustrated in Figure 1. Future Activities All the objectives have now been addressed. University of Michigan graduate studentYan Dong will be presenting the results atThe Minerals Metals and Materials Science TMS conference in 2015 and two publica- tions are in preparation for submission to the Journal of Nuclear Materials. Within the light water reactor susceptibility program understanding the microstructures developing in austenitic stainless steels under very low dose rates is essential to ensuring reliable predictions.