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TEM investigation of Ag diffusion mechanisms in [beta]-SiC fuel particle materials
Thesis   Open access

TEM investigation of Ag diffusion mechanisms in [beta]-SiC fuel particle materials

Robert A. Coward
Master of Science (M.S.), Drexel University
Dec 2012
DOI:
https://doi.org/10.17918/00009359
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Abstract

Nuclear fuels Reactor fuel reprocessing Materials Science
The nuclear industry is on the verge of creating and implementing a new generation of reactors that are meant to be safer and more efficient. One of the new fuel designs utilizes tri-structural isotropic (TRISO) fuel particles. P-silicon carbide (SiC) is the main layer for metallic fission product retention in TRISO fuel particles. However, under the extreme environment of a nuclear reactor, these particles can fail with the release of fission products into the containment vessel of the reactor. There is a need for the tracking of these fission products in the SiC layer to provide support that it is a safe fuel type for a new generation of nuclear reactors. At these elevated temperatures, the only true way to determine the mechanism for Ag mobility is through the use of heating in situ TEM experiments. With this paper, we explore the advantages of using this powerful technique. In this study the microstructural evolution of the beta-sic layer is examined by ion implantation of Ag and annealing samples up to 1600 C. Under examination in the transmission electron microscope (TEM) faceted voids were observed around the Ag particles post-annealing. This gives way to the possible theory of a void mediated transport mechanism due to the change in microstructure of the beta-sic layer at elevated temperatures. In addition, the implanted Ag particles appear to agglomerate during annealing. It was found that the implanted Ag particles are mobile at 1000 C and their mobility appears to be driven by the recrystallization of the amorphized beta-sic.

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