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 Page 153 Page 154 Page 155 Page 156 Page 157 Page 158 Page 159 Page 160 Page 161 Page 162 Page 163 Page 164 Page 165 Page 166 Page 167 Page 168 Page 169 Page 170 Page 171 Page 172 Page 173 Page 174 Page 175 Page 176 Page 177 Page 178 Page 179 Page 180 Page 181 Page 182 Page 183 Page 184 Page 185 Page 186 Page 187 Page 188 Page 189 Page 190 Page 191 Page 192 Page 193 Page 194 Page 195 Page 196 Page 197 Page 198 Page 199 Page 200 Page 201 Page 202 Page 203 Page 204 Page 205 Page 206 Page 207 Page 208 Page 209 Page 210 Page 211 Page 212 Page 213 Page 214 Page 215 Page 216 Page 217 Page 218 Page 219 Page 220 Page 221 Page 222 Page 223 Page 224 Page 225 Page 226 Page 227 Page 228 Page 229 Page 230 Page 231 Page 232 Page 233 Page 234 Page 235 Page 236 Page 237 Page 238 Page 239 Page 240 Page 241 Page 2422016 | AFC ACCOMPLISHMENTS 60 Accomplishments: Two sets of in-situ and ex-situ experi- ments were performed at the X-ray Powder Diffraction (XPD) beamline at the National Synchrotron Light Source-II (NSLS-II). High energy (66 keV) x-rays were used to probe UO2+x samples as a function of stoichiometry and applied voltage.The experimental set up included a spring loaded sample holder encapsulated in a double quartz cell, fitted with gas feed lines, electrical leads and thermocouple (as shown in Figure 1). Patterns were collected in both static-mode, to spatially determine the crystallographic phase as a function of position between the contacts, and in dynamic mode where the sample was fixed and patterns were collected as a function of time through the FAS process.We also performed dynamic- mode tests while scanning the beam between the contacts during the FAS process.The collection of the diffrac- tion patterns (over 100,000 patterns in total) was performed in transmis- sion mode with 1.0s acquisition time with a Perkin Elmer flat panel detector. The Rietveld analysis of the diffraction patterns and extraction of the lattice parameters was performed using dedi- cated high-throughput python scripts that interface withTOPAS (Bruker). The lattice parameters were quan- titatively determined for the many various samples measured.A typical FAS curve is shown in Figure 2 with corresponding XRD peaks collecting over the FAS cycle shown in Figure 2 b.The changes in peak position, and lattice dynamics were quantified through Rietveld analysis.An example of the lattice dynamics is shown in Figure 3 for three different UO2+x sample compositions (UO2, U4O9 and a ~50/50 mixture of UO2 and U4O9) during the flash experiments. The time when the field was applied is shown for reference.The in situ behavior of the samples show that there is an incubation period prior to the flash event.The incubation period is characterized by an initial increase in the lattice parameter.The samples are not highly conductive during this time and the length of the incubation period is related to the applied voltage. The incubation period was observed in all samples, with minimal (to no) increase in the temperature. Such structural changes are indicative that the number of lattice defects increases prior to the onset of the flash event and may be composition independent. Figure 3 also shows that following the incubation period there is a very- rapid increase in the lattice expansion during the flash event for all composi- tions.This expansion coincides with Figure 3. Lattice parameter as a function of time for three different UO2+x samples. The behavior in the different regions are described in the text, and proposed model is shown below in Figure 4.