b'Light Element Analysis ofA new capability furthers understanding of how oxide fuel performs in a reactor Nuclear Fuels by Electronand how fission products migrate within the fuel.ProbeMicroanalysis T he purpose of this project was to develop a cost-effective method to use electron probe microanalysis (an X-ray based technique) to quantify the carbon and oxygen quantities with the spatial resolution of a few micrometers in uranium-based nuclear fuel. In oxide fuels, the oxygen-to-uranium ratio evolves during irradiation and affects fuel properties such as thermal conductivity and fission product oxidation state. Decreasing thermal conductivity TOTAL APPROVED AMOUNT:results in hotter fuel, which enhances fission product transport and increases $128,000 over 3 years fuel swelling. Increased fuel swelling can lead to cladding compromise or failure. Therefore, it is important to understand how the oxygen-to-uranium ratio varies PROJECT NUMBER:spatially across the sample and how it varies with increased temperature and 19A41-025 burnup. The average oxygen-to-uranium ratio for an irradiated fuel pin can be PRINCIPAL INVESTIGATOR:measured using bulk analysis techniques. Being able to quantify the oxygen-to-Karen Wright uranium ratio on the micrometer scale is novel.CO-INVESTIGATORS: Several objectives were achieved during this project, including determining the Fidelma Di Lemma, INL extent to which carbon and oxygen X-rays are absorbed by uranium, determining Jacob McMurray, Oak Ridgethe accuracy that is possible when measuring oxygen in uranium fuel, and testing National Laboratory different X-ray matrix correction models, which are necessary to reduce the electron-physics-based artifact impact on data quality. After some preliminary experiments, COLLABORATOR: high-quality uranium dioxide was obtained and used to determine oxygen X-ray University of Barcelona absorption in uranium, to determine the mass absorption coefficient from that data, and to then test the newly acquired mass absorption coefficient on the measurement of non-stoichiometric uranium dioxide. In addition, issues challenging carbon quantification in uranium and steps to address these challenges were identified.(a) Uranium oxide (U3O8) grain mount calculated to have an oxygen k-alpha mass absorption coefficient in uranium of 7494. (b) U3O8 bulk sample calculated to have an oxygen k-alpha mass absorption coefficient in uranium of 6954.34'