Oxide evolution on the SiC layer of TRISO particles during extended air oxidation

• Published in: Journal of nuclear materials 2022-01, Vol.558 (C), p.153385, Article 153385
• Main Authors: Bratten, Adam, Jalan, Visharad, Gerczak, Tyler, Wen, Haiming
• Format: Article
• Language: English
• Subjects: Air temperature; Atomic force microscopy; Crystal defects; FIB; Fuels; High temperature air; High temperature gases; Ion beams; Microscopy; Microstructure; Morphology; Nuclear fuels; Nuclear reactors; Oxidation; Porosity; Reaction kinetics; Scale (corrosion); Scanning electron microscopy; SiC; Silicon carbide; TRISO
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2021.153385

Tristructural isotropic (TRISO) fuel particles have been primarily developed for high-temperature gas-cooled nuclear reactors and can be subjected to oxidizing environments for extended periods in an off-normal accident scenario. Surrogate TRISO fuel particles were oxidized in air at 1,000 or 1,100 °C for up to 120 h. The oxide scale morphology and thickness were studied via scanning electron microscopy, focused ion beam, and atomic force microscopy. TRISO particles oxidized at 1,100 °C exhibited a highly crystalline oxide scale, which led to significant cracking and irregularly shaped closed porosity, whereas those oxidized at 1,000 °C possessed a primarily amorphous oxide scale, which contained small, rounded internal pores and no larger defects. The observed phenomena deviated from the expected behavior based on models for oxide growth on flat-plate and fiber SiC. The oxidation kinetics of TRISO fuel particles in high-temperature air were investigated without mechanically deforming the surface and were analyzed with respect to oxide morphology. [Display omitted]