Evaluation of Internal Structure Effects on Thermal-Hydraulic Behavior in a Sodium-cooled Pool Type Reactor

Under a Mid- and Long-term Nuclear R and D Program, various conceptual design options for a sodium-cooled fast reactor have been proposed to fulfill the safety criteria and secure a reliable decay heat removal performance. Every design option has its own features to enhance and secure a decay heat removal performance. In the recently proposed reactor pool design for a 600MWe demonstration reactor, DHX was positioned in the hot pool, and the baffle plate was removed. The one of the important design point in this concept is the flow-guide, which induce the stack effects. Stack effect is the phenomenon caused by pressure and temperature differentials which results in fluid being drawn through stack. In this geometry, the flow-guide is installed in the hot pool and partially divides the hot pool into two regions such as UIS region and annular region. In this study the effects of the flow guide on thermal-hydraulic behaviors of reactor pool are investigated numerically. A complex geometrical arrangement in the reactor pool was modeled in COMMIX-1AR/P using a porous-medium approach. In order to estimate the effects of flow-guide in the reactor pool, the imaginary reactor having the same geometry except flow-guide is modeled additionally. The overall thermal-hydraulic behaviors in the reactor pool have been evaluated at a steady state condition and the effects of flow-guide are discussed