A CFD analysis of coolant flow in a PWR lower plenum without geometrical simplification

Numerous simulations and safety analyses for nuclear power plants (NPPs) are performed during the period from the design stage to commercial operation in order to ensure the safe operation of NPPs. In general, the simulations are carried out using vendor-specific design codes and best-estimate system analysis codes such as MARS, RELAP, TRAC and CATHARE. Most of these system codes were developed based on 1-dimensional lumped parameter models in order to reduce computing expenses. During the past decade, however, computers and 3-dimensional (3-D) computational fluid dynamics (CFD) codes have been dramatically enhanced. It is believed to be beneficial to take advantage of advanced commercial CFD codes in safety analysis and design of NPPs. The present work aims to analyze the flow distribution in downcomer and lower plenum of Korean standard nuclear power plants (KSNPs). The lower plenum geometry of a PWR is very complicated since there are so many reactor internals, which hinders in CFD analysis for real reactor geometry up to now. The present work takes advantage of 3D CAD data for the KSNP so that real geometry of lower plenum without geometric simplification is used. The STAR-CD, a commercial CFD code, is used to analyze flow and pressure distribution in this work. The results give a figure about flow distribution in reactor vessel, which is one of major safety concerns. The calculated pressure drops across certain sections were evaluated to compare with the values in design sheet. (authors)