2018 | AFC ACCOMPLISHMENTS 159 Figure 2. Transverse cross section of AFC-3D R5 (U-4Pd-13Zr, 55% smear density, annular, He bonded, 2.9 atom % burnup). This fuel has performed well with high additive loading which demonstrates the need to balance additive loading with excess Zr to ensure good early life fuel performance. the historical fuel performance of previously irradiated fuel from literature. Fuel performance was irradiated through a suite of PIE techniques including neutron radiography, gamma spectrometry, dimensional inspection, fission gas release measurements, chemical burnup analysis, and optical microscopy.The examinations took place at Idaho National Laboratory These postirradiation exams have highlighted important technological data necessary to enable once though sodium fast reactor fuel that do not have sodium bonded fuel. at the Materials and Fuels Complex (MFC), Hot Fuel Examination Facility (HFEF) andAnalytical Laboratory.The irradiations were performed at relatively aggressive temperatures that resulted in significant interaction between the cladding and the fuel in many cases. In spite of this, there were no in-pile cladding breaches in these tests.The U-Zr alloys performed better than the U-Mo or U-Mo-Ti-Zr alloys. Some of the fuel-cladding interaction issues seen in helium bonded annular fuel that was not machined to tight tolerances appear to have been resolved by machining the outer diameter of annular fuel in this irradiation. Higher Zr concentrations in additive bearing fuel appear to have improved the performance of Pd additive fuel.