Microstructure Evolution of U-Zr System in A Thermal Cycling Neutron Diffraction Experiment: Extruded U-10Zr (wt. %)

Microstructure evolution of 1073 K extruded U-10Zr (wt. %) fuel during thermal cycling (303-1073 K with a similar to 9 hour hold at 873 K during cooling) was investigated using in situ neutron diffraction. Analysis was performed using Rietveld texture and crystal structure refinements from time-of-flight neutron diffraction data, with a focus on the evolution of textures and lattice parameters as a function of temperature. The alpha-U phase exhibits lattice contraction with increasing temperature along the b lattice direction and lattice expansion in the other directions while the other phases exhibit lattice expansion with temperature in all directions. Contrary to the established phase diagram, the beta-U phase is absent at the temperatures of the thermal cycling. (001)(alpha) and (110)(gamma) plane normals are observed with a strong preferred orientation along the extrusion direction. The variant selection of (001)(alpha)parallel to(110)(gamma) is observed for the first time. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The microstructure evolution of 1073K extruded U-10Zr fuel during thermal cycling was investigated using in situ neutron diffraction. The alpha-U phase exhibits lattice contraction in the b direction and lattice expansion in other directions with increasing temperature, while other phases exhibit lattice expansion in all directions with temperature. Contrary to the established phase diagram, the beta-U phase is absent during the thermal cycling.