Relocation of Molten Zircaloy in a CANDU Subchannel Geometry

Abstract

The results of the experiments described in this paper helped identify two mechanisms that will restrict bundle temperature escalation in those postulated CANDu nuclear power reactor accidents in which considerable heat is generated by the Zr/steam reaction. One mechanism involves the formation of a zirconium oxide crucible around the fuel--pins and the other, there location of molten sheath within the crucible. Both mechanisms result in a reduction in the area of Zircaloy-4 sheath exposed to the steam. Because the rate of heat generation during a reaction is proportional to area, reduction in the area of exposed sheath will limit the temperature escalation during an accident.