The graphite-fuel matrix in the core region of HTGRs can come into direct contact with air at high temperature during air ingress accident. Nuclear grade graphite has been shown to undergo oxidation when subjected to oxidizing flow at high temperatures. There is, however, no agreement on the relative importance of the numerous factors that can contribute to the overall rate of oxidation. Examples of some of these potential factors include graphite temperature, fluid temperature, fluid composition, graphite composition, and graphite surface conditions. Separate effects experiments have, in general, not been able to fully capture these complex interactions.
In this work, a new experimental apparatus was designed to conduct mixed-effect experiments to understand the complicated interactions that would influence the oxidation rate and heat removal rate of graphite exposed to a high temperature air ingress. Utilizing thermographic methods, experiments detailing the local temperature response of a representative graphite flow channel were conducted at high temperatures (1173 K) in both oxidizing and inert gaseous environments.