Texture Analyses and Microstructural Evolution in Monolithic U-Mo Nuclear Fuel

This work describes the microstructural evolution of prototypical monolithic U-Mo fuel plates analyzed via scanning electron microscopy and electron backscattered diffraction (EBSD). The understanding of the microstructural and textural evolution of nuclear fuel from as-fabricated to post-irradiation is important in assessing changes in material properties during irradiation. In our work it was observed that the typical fabrication techniques applied in U-10Mo monolithic fuel plates develop features associated with a cold-rolled body-centered cubic (bcc) texture and development of alpha and gamma fiber (parallel to the rolling and normal direction). After irradiation, a loss of the fabrication-induced preferred orientation was observed with an increased spread of grain-boundary misorientation as burnup increases. Grain subdivision was observed in the irradiated samples with the formation of submicron grains (200-500 nm). Evidence for polygonization as the mechanism leading to grain subdivision was detected. This has been observed for the first time for U-Mo monolithic fuel via EBSD and has been associated to formation of low-angle grain boundaries (<15 degrees) at the site of the submicron grains. Such analyses of the microstructural and textural evolution of fuel (from fabrication to after irradiation) have the potential to help develop and validate microstructural physics-based models and provide a key feedback loop to further understand the interplay between fabrication processes and fuel performance. (C) 2020 Elsevier B.V. All rights reserved.