In case of severe accident when core melt is ejected
from vessel, external core catcher has been considered in APR1400 reactor.
Two-phasenatural circulation basedcore catcher cooling system removes decay
heat of corium to increases the reliability and safety. KAERI (Korea Atomic
Energy Research Institute) have developed core catcher concept which operates
as a passive system. As coolant flows through single channel below the core
catcher plate, bubbles are generated due to decay heat and a two-phase flow is
established.In order to stabilize the corium effectively and avoid critical
heat flux (CHF) at the plate surface, it is necessary to understand two-phase
flow behavior in the cooling channel.