2018 | AFC ACCOMPLISHMENTS 111 Figure 2. Setting up for fuel rodlet welding within the laser welder. In addition to the novel ATF concepts, the first insertion of the ATF-2 test train included several fuel rodlets with standard UO2 fuel and Zr-4 cladding to serve as reference specimens for future irradiation testing in Idaho National LaboratoryINL’s transient test reactor (TREAT). Some of these UO2/ Zr-4 fuel rodlets may also serve as standard points of comparison with ATF concepts during postirradiation examination (PIE), given the well characterized performance of this fuel system. INL fabricated a majority of the test specimens, while others were provided by industry collaborators and qualified for reactor insertion at INL Accomplishments: The ATF-2 campaign set ambitious goals with the first insertion of the test train both with the quantity and with the variety of fuel rodlets. In total INL was responsible for, and successful in, the fabrication and assembly of fifteen rodlets and receipt and qualification of an additional eleven rodlets. Building upon lessons learned from previous irradiation experiment fabrication efforts, the assembly of ATF-2 fuel rodlets employed laser welding as a more reliable and robust assembly method than convention