b'Characterization and Performance of SiC/SiC TubesPrincipal Investigator: Takaaki Koyanagi (ORNL)Team Members/ Collaborators: Christian M. Petrie, Peter A. Mouche, Xunxiang Hu, Jos D. Arregui-Mena, and Yutai Katoh (ORNL)Project Description: The objective of this research is to understand the effects of neutron irradiation on the hermeticity of prototypic SiC/SiC composite clad-ding and to develop a mitigation coating on the outer surface of the cladding. Understanding radiation effects helps predict fuel perfor-mance with SiC/SiC composite cladding systems for reliable reactor operations. The coating technology could be critical for safely operating S iC fiber-reinforced SiC matrixand extending the lifetime of SiC-(SiC/SiC) composite tech- based cladding. nologies have exponentiallyThis project conducted post-irradi-advanced for accident-tolerant fuelation examination (PIE) of several cladding applications in light waterprototypic SiC/SiC composite tubes Figure 1. (Left) Schematicreactors (LWRs). Recent researchwith different fiber architectures. illustration of the flash diffusivityand development have improvedNeutron irradiation in the High Flux test; (right) the SiC/SiC composite tube after specimen preparation forthe tube processing technologyIsotope Reactor (HFIR) at ORNL was thermal diffusivity measurement and advanced understanding of theconducted by using a novel radiation thermomechanical behavior of thevehicle that generated a temperature cladding under normal and off- gradient across the tube thickness normal operating conditions. A teamto simulate a radiation environment at Oak Ridge National Laboratoryof LWR fuel rods. Comprehensive (ORNL) is addressing the remainingmicrostructure and physical property technology challengethe potentialcharacterizations were conducted loss of fission gas retention due toat ORNLs Low Activation Materials cracking under normal operatingDesign and Analysis Laboratory. The conditionsby understanding mate- correlation between the microstruc-rial degradation mechanisms andture and hermetic properties provides developing mitigation technologies. important feedbacks on how to opti-76 2021|AFC ACCOMPLISHMENTS'