Investigations on Sodium Boiling Accidents in a Large Fast Breeder Reactor, (I)

The radial propagation of sodium boiling by thermal process in a 1,500 MWe FBR is analyzed with the BOIP-T code. Since the model used embodies some uncertainty, several modes of molten fuel behavior are considered. The time required for boiling to propagate from one channel to its neighbor is calculated. Even on the most conservative basis, the boiling propagation requires at least 10 sec, which indicates that the radial propagation of sodium boiling could be prevented by a suitable core protection system.