Investigation of the stability of TRISO particle fuel under accident scenarios will aid in furthering the advancement of this fuel type. During an accident scenario, oxidants can be introduced to the core and expose the fuel compacts to an oxidizing atmosphere. The compromised compact could allow for low partial pressures of the oxidants to be introduced to the TRISO particles, specifically the silicon carbide (SiC) layer. The SiC layer acts as both the primary structural component of the TRISO particle and barrier to fission product release. Exposure of this layer to an oxidizing atmosphere could either cause SiC recession or the formation of a potentially passivating oxide layer depending on oxidant partial pressures and temperature. Degradation of the SiC can lead to the release of fission products present in oxidized layers into the compact. The investigation proposed will explore the impact of irradiation on the oxide layer formed during oxidant exposure. The data provided will inform on any variations in the surface chemistry and microstructure in the SiO2 layer formed from different oxidant exposures and how irradiation impacts the evolved microstructure.

Efforts outlined in the proposal aligned with the Department of Energy’s Office of Nuclear Energy’s goals to advance research in the technological advancement of advanced reactor types. TRISO particles are a candidate fuel form for various advanced reactors, including high-temperature gas-cooled reactors. Characterizing irradiated and unirradiated particles will provide precision measurement of microstructural features of relevance to the performance of these fuel concepts during various oxidant ingress scenarios. The results from this experiment will also aid in NEAMS efforts by informing fuel performance models on the oxidation behavior of the TRISO particles. This will further the efforts to further the qualification of this fuel form for various advanced reactor designs.