Atom Probe Tomography of Segregation at Grain Boundaries and Gas Bubbles in Neutron Irradiated U-10 wt% Mo Fuel

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During neutron irradiation to fission densities > 5.2 × 1021 fiss/cm3, Xe agglomerates forming gas bubbles of varying size within the U-Mo fuel matrix. Herein, segregation of fission products to Xe bubbles and grain boundaries (GB) were studied using atom probe tomography (APT). Segregation behavior was found to vary among GBs, small bubbles (< 10 nm), and larger bubbles (>10 nm). Solid fission products were enriched at GBs and larger bubbles, but not at small bubbles. A denuded zone was identified adjacent to a > 10 nm Xe gas bubble and a GB.