b'Figure 3. Researcher Walter Williams preparing for neutron diffraction at LANLs lujan neutron scattering centers high-pressure-preferred orientation beamline.of both phase transformations andthe re-evaluation of reactor safety phase transformation kinetics in themargins and operating conditions. system. The samples included variousTEM analysis with in-situ heating is alloys ranging from U-6wt%Zrongoing and intends to couple the to U-30wt%Zr, corresponding toatomistic neutron diffraction data to compositions observed in-pilethe nanostructure present in the fuel. following constituent redistribu- The highly controlled out-of-pile test tion. As phase transformations areconditions can then be contrasted a key factor in the occurrence ofwith the postirradiation character-constituent redistribution, the under- ization to deconvolute thermal and standing of them is subsequentlyneutronic effects on the microstruc-critical in the accurate predictionture. While the pre-irradiation char-of temperature-to-melt, a key safetyacterization data has been collected, factor in all nuclear fuels. Increasingthe characterization itself is ongoing.this understanding will allow for 2019|AFC ACCOMPLISHMENTS 211'