Abstract
Surrogate tristructural-isotropic (TRISO)-coated fuel particles were oxidized in 0.2 kPa O2 at 1200–1600°C to examine the behavior of the SiC layer and understand the mechanisms. The thickness and microstructure of the resultant SiO2 layers were analyzed using scanning electron microscopy, focused ion beam, and transmission electron microscopy. The majority of the surface comprised smooth, amorphous SiO2 with a constant thickness indicative of passive oxidation. The apparent activation energy for oxide growth was 188 ± 8 kJ/mol and consistent across all temperatures in 0.2 kPa O2. The relationship between activation energy and oxidation mechanism is discussed. Raised nodules of porous, crystalline SiO2 were dispersed across the surface, suggesting that active oxidation and redeposition occurred in those locations. These nodules were correlated with clusters of nanocrystalline SiC grains, which may facilitate active oxidation. These findings suggest that microstructural inhomogeneities such as irregular grain size influence the oxidation response of the SiC layer of TRISO particles and may influence their accident tolerance.
| Original language | English |
|---|---|
| Pages (from-to) | 3922-3933 |
| Number of pages | 12 |
| Journal | Journal of the American Ceramic Society |
| Volume | 106 |
| Issue number | 6 |
| DOIs | |
| State | Published - Jun 2023 |
Funding
The authors would like to thank Dr. Rachel Seibert for her thoughtful review of this manuscript. The MATLAB script used for measuring the oxide thickness in the cross-section micrographs was developed by Grant Helmreich at Oak Ridge National Laboratory. SEM, FIB, and (S)TEM works were supported by the University of Missouri Electron Microscopy Core “Excellence in Electron Microscopy” award. This study was financially supported by the Nuclear Energy University Program (award number DE-NE0008753) under the Office of Nuclear Energy of the US Department of Energy. H. M. Wen also acknowledges the US Nuclear Regulatory Commission Faculty Development Program (award number NRC 31310018M0044). The authors would like to thank Dr. Rachel Seibert for her thoughtful review of this manuscript. The MATLAB script used for measuring the oxide thickness in the cross‐section micrographs was developed by Grant Helmreich at Oak Ridge National Laboratory. SEM, FIB, and (S)TEM works were supported by the University of Missouri Electron Microscopy Core “Excellence in Electron Microscopy” award. This study was financially supported by the Nuclear Energy University Program (award number DE‐NE0008753) under the Office of Nuclear Energy of the US Department of Energy. H. M. Wen also acknowledges the US Nuclear Regulatory Commission Faculty Development Program (award number NRC 31310018M0044). This manuscript has been authored by UT‐Battelle, LLC, under contract DE‐AC05‐00OR22725 with the US Department of Energy (DOE). The US government retains, and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid‐up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe‐public‐access‐plan ).
Keywords
- SiC
- TRISO particles
- electron microscopy
- high temperature
- oxidation