An analysis of the air-graphite reaction in the VHTR core on the accident of air ingress

In the case of a large rupture accident in the primary coolant system of VHTR, it will be necessary to suppose the long term graphite oxidation in the reactor due to the air ingress with natural convection. Therefore, the accident analysis code for the evaluation of graphite oxidation accident has been developed. The results of the analysis on the basis of VHTR conditions show that the portion of graphite with higher temperature and with higher oxygen partial pressure has the larger loss of the surface, and that the portion of graphite with lower temperature and with higher oxygen partial pressure has the deeper burn-off effect. (author)