Density Change of Reactor Graphites as a Result of the Graphite/Oxygen Reaction in the Pore Diffusion Region

[Automatically extracted and translated] Carbon in the form of graphitic material is used for essential primary circuit components in gas-cooled high-temperature reactors (HTR) due to its excellent thermal, mechanical, and neutron-physical properties. Part of the HTR-specific spectrum of incidents is associated with the ingress of air into the HTR primary circuit and its chemical reaction with the hot graphite. Due to the extremely low probability of occurrence of such incidents, they are also referred to as 'hypothetical' incidents. Hypothetical air ingress incidents have been extensively investigated, with statements focusing on the influence on thermodynamics, graphite erosion, and the formation of combustible gases. In the course of these investigations, kinetic data of the reaction with oxygen in the 'pore diffusion region' were experimentally determined on various graphitic materials for the German HTR concepts. At the end of the kinetic experiments, density profiles are measured in the area of the corroded surfaces of the graphite samples. The presentation and evaluation of these measurement results is the subject of this report.