| Abstract Scope |
The silicon carbide (SiC) layer in TRISO fuel particles acts as the primary barrier to fission product release and is essential to the safety and longevity of High-Temperature Gas-Cooled Reactors (HTGRs). Under steam ingress accident conditions, the SiC layer becomes directly exposed to elevated temperatures and a mixed-gas atmosphere. This can result in active oxidation, which leads to the recession of the SiC layer, increasing the risk of fission product release as this layer thins. Accurately measuring the thickness of the SiC layer is challenging due to the small size and complex multilayer spherical structure of the TRISO particle. In addition, inherent thickness variability within single particles as well as between different particles due to the deposition process complicates consistent direct measurements using conventional methods. Therefore, this research evaluates Raman Spectroscopy as a novel, non-destructive approach to quantify SiC recession and compare the results to the previous study (Electron microscopy-based methods, Shadow imaging via optical microscopy). This work utilized TRISO surrogate particles from Oak Ridge National Laboratory (ORNL), specifically from the AGRBW-4A2 lot, with a ZrO₂ kernel and without buffer or OPyC layers, allowing direct evaluation of SiC oxidation behavior. Our results shed light on how factors such as high temperature, oxidant partial pressure, and oxidation duration influence SiC behavior under steam oxidation conditions, thereby improving our understanding of TRISO fuel performance under extreme accident scenarios and supporting the development of safer, more resilient nuclear fuel systems. |