Kinetic modeling of IG-110 oxidation in inert atmosphere with low oxygen concentration for innovative high-temperature gas-cooled reactor applications

The oxidation behavior of IG-110, a graphite core component, was investigated at temperatures ranging from 400 to 1000 degrees C in a 10 ppm Ar/O-2 flow to simulate the oxidation process between the graphite core component and helium coolant with low O-2 concentrations employed in advanced High-Temperature Gas-cooled Reactors (HTGRs). The results reveal that IG-110 undergoes significant mass loss at temperatures above 700 degrees C, resulting in total mass changes of -1.5%, -5.3%, and -9.0% at 700, 800, and 1000 degrees C, respectively, during a 10-hour oxidation period. No significant mass loss is observed below 600 degrees C. To understand the oxidation mechanism of IG-110 under low O-2 concentrations, we propose a kinetic model as the current chemical kinetic-controlled model does not fully explain the oxidation behavior observed in our research. Our analysis shows lower estimated reaction rates compared to studies at higher O-2 concentrations; the activation energy values exhibit good agreement. The proposed kinetic model sheds light on the oxidation mechanism of IG-110 under 10 ppm Ar/O-2 flow. This study provides new insights into the oxidation behavior of graphite core components in HTGRs and highlights the importance of controlling the O-2 concentration in the helium coolant to prevent severe degradation of SiC-matrix fuel compacts.