Numerical analysis of graphite oxidation and thermohydraulics of air ingress accidents in htgrs

摘要

In primary coaxial pipe rupture accidents in HTGR, air enters the reactor pressure vessel (RPV) due to the natural circulation developed after pressure equalization between the outside and inside of the RPV, and oxidizes graphite components such as fuel elements and reflector-blocks. The amount of oxidation of the graphite components in a reactor is a major concern in safety evaluations. A computer program to calculate simultaneously the natural circulation of a multicomponent gas mixture, as well as chemical reactions and the change in composition of the component gas mixture, has been developed and calculation results has been verified through a comparison with experimental results. The calculation results show good agreement with the experimental results.