Investigation of the microstructure evolution of alpha uranium after in pile transient

This work describes the microstructural evolution of textured alpha uranium (alpha-U) specimens under different reactor transients achieving very low burn-up. The understanding of the behavior of this single phase will provide important information to further the material knowledge of metallic fuels (e.g. UPu-Zr, U-10Zr). Such alloys are of interest for their application in advanced reactor concepts. In metallic fuels a-U is, indeed, a relevant phase. Moreover, data on fuel behavior during early-stage irradiation are generally lacking and are important to validate and develop modelling and simulation tools. Characterization of grain boundaries, texture evolution, and phase transformation were obtained through scanning electron microscopy coupled with electron backscattered diffractometry and transmission electron microscopy.The data obtained indicates that phase transformation and microstructural change (e.g. recrystallization/grain growth) can occur during rapid transient even at low burn up. It is likely that the residual strain in the as-fabricated alpha-U specimens and the thermal strain introduced by reactor transients played an important role in the recrystallization of the alpha-U phase, as well as retaining the beta-U phase at room temperature. (C) 2020 Elsevier B.V. All rights reserved.