A critical review of the microstructure of U–Mo fuels

The microstructure of fuels evolves with irradiation and extensive microstructural characterization has been performed both on as-fabricated and irradiated U–Mo fuels for both dispersion and monolithic designs since initiation of the program to transition research reactors around the world from using high enriched uranium to low enriched uranium fuels. Developing mechanistic understanding of the U–Mo fuel microstructure and properties, which ultimately govern fuel performance during reactor operation, is an important part of the fuel qualification effort. With recent progress in implementation of modern characterization techniques in nuclear fuels research, a critical review of these efforts is warranted. In this review article, the authors provide a compilation and impartial assessment of the available experimental data involving microstructural evolution of U–Mo fuels, gaps in fundamental understanding of irradiation-induced phenomena, and outline path forward for fuels research. This article is intended as a resource for fuel designers and modelers that recaps recent research trends and a guide for prioritizing future experimental work on U–Mo fuels.