Carryover characteristic during reflood process in large scale separate effects tests

Abstract

A study on carryover characteristic in the core and upper plenum during the reflood phase in PWR-LOCA was performed with the use of data from the slab core test facility (SCTF) having eight rod bundles scale. Void fraction distribution in the core was strongly related to quench propagation in rod bundles. A correlation for mass effluent rate out of core was derived from the void fraction distribution characteristic. The correlation was found to be widely applicable. On the other hand, the capture of entrained liquid in the upper plenum by structures and water pool is below 30% of the entrainment mass flow rate during most of the reflood phase and increase when the steam velocity decreases. Since entrainment rate into hot leg increases with increase of liquid flow out of the core, the reflood velocity should tend to be suppressed with time because of stronger steam binding effect.