Microstructure of TRISO coated particles from the AGR-1 experiment: SiC grain size and grain boundary character

• Published in: Journal of nuclear materials Vol. 432; no. 1-3; pp. 127 - 134
• Main Authors: Kirchhofer, Rita, Hunn, John D., Demkowicz, Paul A., Cole, James I., Gorman, Brian P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-01-2013; Elsevier
• Subjects: Applied sciences; Chemical vapor deposition; Controled nuclear fusion plants; Electron back scatter diffraction; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Grain boundaries; Grain size; Installations for energy generation and conversion: thermal and electrical energy; Lattices; Microstructure; Nuclear fuels; Silicon carbide; Transmission electron microscopy; Grain size; Silicon carbide; Coated particle; Microstructure; Gas cooled reactor; Chemical vapor deposition; Grain boundary; Nuclear reactor
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2012.08.052

► Microstructural differences in the SiC of TRISO fuel types were evaluated. ► Grain size determination performed via EBSD and TEM. ► SiC grain size was consistent for particles produced using H2 gas for fluidization. ► A refined microstructure was found for SiC produced using H2+Ar for fluidization. ► Differences in GBCD were observed in the different fuel types via EBSD analysis.
Pre-irradiation SiC microstructures in tristructural-isotropic (TRISO) coated fuel particles from the Advanced Gas Reactor Fuel Development and Qualification program’s first irradiation experiment (AGR-1) were quantitatively characterized using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). From EBSD, it was determined that only the cubic polymorph of as-deposited SiC was present and the SiC had a high fraction of coincident site lattice (CSL) Σ3 grain boundaries. Additionally, the local area misorientation (LAM), which is a qualitative measurement of strain in the SiC lattice, was mapped for each sample fuel variant. The morphology of the SiC/IPyC interfaces were characterized by TEM following site-specific focused ion beam (FIB) specimen preparation. It was determined that the SiC layer had a heavily faulted microstructure typical of chemical vapor deposition (CVD) SiC and that the average grain diameter increased radially from the SiC/IPyC interface for the samples manufactured with similar CVD conditions, while the last sample showed a nearly constant grain size across the layer.