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Numerical simulation of VVER type reactor internal flow and optimization of the flow diffuser with Code Saturne

Abstract:

In the pressurizer water reactor (PWR) vessel, the coolant flow field is very complex due to the presence of various internal structures, especially in the lower plenum. Different types of current reactors have distinct designs, such as EPR, VVER, APR+ and AP1000. The lower plenum structures have a significant influence on the coolant flow field and flow rate distribution at the core inlet. From the safety point of view, a homogeneous core inlet flow distribution is expected. Xi’an Jiaotong University and EDF proposed a project recently, which aims to study and optimize various PWR flow diffusers using computational fluid dynamics (CFD) methodology. In this paper, the numerical simulation of VVER type reactor internal flow is reported. PIRT (Phenomena Identification and Ranking Table) is used to identify the main phenomena and key parameters related to the coolant internal flow and the flow rate distribution at the core inlet. According to the PIRT analysis, two structural parameters considered to have great influence on the core inlet flow rate distribution are analyzed, which are the shape of the bottom wall and the flow channel constriction rate in the lower plenum. The geometry models and meshes of each parameter are generated using Salome platform, and the CFD simulations are performed using the EDF open source software Code_Saturne. Three dimensional coolant flow fields in the lower plenum are obtained and the calculated results are discussed in respect of the core inlet flow rate distribution. The present work can provide useful information for the flow diffuser optimization and new design study.