Transmission electron microscopy investigation of Ag diffusion mechanisms in β-SiC

beta-Silicon carbide (beta-SiC) acts as the main layer for metallic fission product retention in tristructural-isotropic (TRISO) fuel particles. It is critical to track these fission products in the beta-SiC layer to provide a baseline understanding of safe fuel operation for next generation nuclear reactors. In this study, the microstructural evolution of the beta-SiC layer is examined through the comparison of as-implanted and annealed samples up to 1600 degrees C using high resolution transmission electron microscopy (HRTEM). Faceted voids were observed in annealed samples but not in the as-implanted samples, suggesting the possibility that a void mediated fission product transport mechanism due to the change in microstructure of the beta-SiC layer at elevated temperatures plays a role in the diffusion of metallic species through the beta-SiC cladding layer. It should be noted, however, that Ag implantation at room temperature is not an ideal method to study Ag diffusion in TRISO fuel particles. Ultimately, Ag implantation should be performed above the critical temperature for which amorphization will not occur to better correlate to conditions in a Generation IV reactor and to see if void formation occurs. (C) 2014 Elsevier B.V. All rights reserved.