Numerical study on the heat transfer phenomena in water pool type reactor cavity cooling system of very high temperature gas-cooled reactor

Many studies have been performed on High Temperature Gas-cooled Reactor (HTGR) which is able to make a mass production of hydrogen with economy and efficiency. The HTGR is designed to remove heat using passive cooling system in order to have an inherent safety and high heat removal capacity during the accident. Therefore, Reactor Cavity Cooling System (RCCS), is installed between the reactor vessel and the containment in cavity, is considered to remove heat during normal operation and accidents. The cooling type of RCCS was divided by cooling method water-cooled and air-cooled type. The concept of the water pool type RCCS, which was proposed at Seoul National University, consists of a reactor vessel, water pool surrounding the vessel, upper tank, cooling pipes and air supply system. It was designed to overcome the disadvantage of both the weak cooling ability of air cooled type and the complex structures of water cooled type. In this study, preliminary numerical analysis for experimental facility was performed to evaluate the proposed RCCS design. CFX was used for modeling of experimental facility and the surface temperature of cooler calculated by RETRAN-3D/INT was used as a boundary condition. The calculation results from CFX and RETRAN-3D/INT show good agreements with each other and it is found that the proposed RCCS design has sufficient cooling capability. (authors)