2018 | AFC ACCOMPLISHMENTS 28 Figure 3. Improved SiC cladding by General Atomics – 1 Meter Tubes, Improved Composite Structure and Hermetic Endplugs. of beyond design basis events and significantly lower fuel cycle costs for the utilities and their customers. Accomplishments: Rapid progress has been made on developing and producing the compo- nents for the LTRs to be inserted in Byron-2 in spring of 2019. These LTRs consists of segments containing U3Si2 pellets in thick-walled Zr tubes and Cr coated Zr alloy tubes containing both ADOPT and UO2 pellets. The U3Si2 pellets were made by INL (Figure 1) and are much improved (few cracks and surface fazing) over previous pellets due to the use of new tooling. The ADOPT fuel will be made byWestinghouse Sweden and the coated cladding by ARL/VRC/MOOG (Figure 2).These components will be assembled atWestinghouse Columbia in the fall of 2018. Progress continues on developing the components for the LTA to be introduced in 2022. This LTA will consist of Cr coated Zr alloy and SiC cladding. The fuel pellets will be oxidation resistant U3Si2, UO2 and ADOPT. Significant progress has been made in the fabrication and character- ization of engineered, multi-layered SiGAtm SiC-SiC-based accident tolerant fuel cladding. Improvements in dimensional control techniques allow for cladding fabrication meeting tolerances of +/-0.001 inch for a given target dimension, while controlling surface roughness to Ra of ~0.5 µm for the outer tube surface and Ra of ~10 µm on the inner surface. Rodlet assembly trials were performed using SiC-SiC composite tubing, springs, pellets, spacers, and thermometry components, and several improvements have been implemented to enable more reliable sealing of SiC-cladding rodlets with an internal helium backfill. Rodlet leak rates better than 1E-9 atm-cc/ sec have been measured, which is well below the leak rate specification. New high-temperature characteriza-