Plutonium-uranium-zirconium (Pu-U-Zr) and plutonium-uranium-molybdenum (Pu-U-Mo) alloys have attracted attention for application in advanced fast reactors. This application demands an understanding of fuel performance and detailed microstructure characterization prior to an alloy’s implementation in nuclear reactor environment. Despite their potential importance as reactor fuels, alloys U, Pu, Zr and Mo have not been thoroughly characterized, and microstructures of unirradiated materials have not been examined in detail. The project aims to characterize the microstructure and chemical composition of these as-cast metal fuel alloys. This proposal requests access to focused ion beam (FIB), transmission electron microscope (TEM), and local electrode atom probe (LEAP) instruments for thorough characterization of fuel microstructure and chemical analysis. The proposed work will lead to enhancement of fundamental understanding of fuel performance.

Technical relevance of the proposal is directly related to the Department of Energy Office of Nuclear Energies mission to advance nuclear power as a resource capable of meeting the nation’s energy, environmental, and national security needs, and the mission to develop next-generation advanced nuclear fuels. The proposed project will benefit The Fuel Cycle Research and Development (FCRD) project, funded by DOE NE and Advanced Fuel Cycle Initiative (AFCI). The potential use of U-Pu-Zr and U-Pu-Mo alloys in fast breeder reactor applications is under consideration. The development of a closed fuel cycle under AFCI, in which metal fuels are used for transmutation of minor actinides, is expediting the research on U-Pu-Zr alloys. Despite the importance of these fuels, detailed description of microstructures in these materials is extremely limited. The majority of published results are based on characterization of as-cast microstructures of these fuels in scanning electron microscopes (SEM). Detailed structural analysis and chemical composition analysis of U-Pu-Zr and U-Pu-Mo fuels is yet to be conducted. The proposed work will allow advanced detailed characterization of the metal fuel microstructure and chemical composition, which will ultimately lead to the development of improved nuclear fuel with enhanced performance.