To improve the heat removal efficiency from the core and achieve the higher power density operation in High Temperature Gas-cooled Reactor, the use of a sleeveless SiC matrix fuel compact shall be proposed. In the present study thermogravimetric test on polycrystalline reaction-sintered SiC and IG-110 graphite was performed to evaluate the oxidation behavior under conditions of air ingress accident. The results showed that graphite oxidation in air was a severe weight loss reaction under elevated temperature. On the contrary, SiC was found to follow passive oxidation mode with a slight weight gain process up to 1400 ℃. Therefore, SiC is suggested as a preferable candidate in comparison to graphite because of its stable anti-oxidation property. The measured reaction rates were well fitted to Deal-Grove model, thus, ideal SiC passive oxidation kinetic was observed. Moreover, the activation energy was determined as 323 kJ/mol for polycrystalline reaction-sintered SiC.

Preventing severe corrosion incidents caused by air ingress accidents in high-temperature gas-cooled reactors (HTGRs) while improving heat removal efficiency from the core is of paramount importance. To enhance both safety and efficiency, a sleeveless silicon carbide (SiC)-matrix fuel compact has been proposed. This study evaluates the 10-hour oxidation of reaction-sintered SiC (RS-SiC)-matrix fuel compact under the conditions of an air ingress accident within the temperature range of 1000 to 1400 °C. The oxidation tests were conducted in a stagnant air environment without flow. As a result, it is demonstrated that RS-SiC exhibits exceptional resistance to air oxidation up to 1400 °C, as shown by the thermogravimetric analysis (TGA), with minimal mass loss due to the oxidation of free carbon. Scanning electron microscopy with energy-dispersive X-Ray spectroscopy (SEM–EDX) analysis reveals that the morphology and thickness of the SiO₂ layer formed on the RS-SiC surface vary with temperature. At 1400 °C, uniform oxide layer thickness ranging from 1.59 to 4.10 μm and localized nodule-like oxide formations of approximately 10 μm are observed. In contrast, at 1000–1200 °C, thinner oxide layers are identified, indicating that oxide growth accelerates at higher temperatures. The oxidation rates measured provide insights into the mechanisms of oxide growth.

I. In a severe nuclear accident scenario, reactor core disruption following serious structural damages may lead to fuel debris formation and spreading, causing radioactive material release inside t...