Oxidation behaviour of the matrix materials in spherical fuel elements

The oxidation resistance of the matrix materials is vital to the normal operation of HTGR and is also an important parameter for evaluating the safety response under accidental air or water-ingress conditions: The oxidation kinetics of the three matrix material components: natural graphite, artificial graphite and resin carbon, was studied in a flowing gas mixture of oxygen and nitrogen using an auto thermogravimetric system. The results indicate that the artificial graphite has the slowest oxidation rate followed by the natural graphite and then the resin carbon with the highest oxidation rate. Vacuum heat treatment of the natural graphite at 1950 °C decreases the impurities and increases the oxidation activation energy. Differences between the activation energy and the oxidation rate of the resin carbon heat treated at 1 950 ° and 1 600 °C resulted from changes in the micro-pore texture and the reduction of impurities.