Nuclear Science User Facilities 76 Silicon carbide fiber-reinforced silicon carbide matrix (SiC/ SiC) composite is an enabling materials technology for the ultimate accident-tolerant fuels for light-water reactors (LWRs) and the core struc- tures for advanced high-temperature reactors of various concepts.This ceramic composite combines the intrinsic benefits of SiC (e.g., outstanding irradiation tolerance and steam-oxidation resis- tance) and the engineered benefits of fiber composites (e.g., damage tolerance and design flexibility). The unique set of benefits for SiC/SiC composite comes with a unique set of challenges.This project addresses one of the most critical challenges, this material’s inability to maintain fission- product-gas containment. Radial Heat Flux – Irradiation Synergism in SiC ATF Cladding Yutai Katoh – Oak Ridge National Laboratory – Figure 1. The “inverse thermal stress” predicted by multiphysics finite element thermomechanical analysis to develop in SiC/SiC tube as the synergistic effect of radial heat flux and neutron irradiation. Assumed conditions include radial heat flux 0.6 MW/m2 and outer surface temperature 573K.