A numerical study for the effect of flow skirt geometry on reactor internal flow

Abstract

A series of 1/5 scale reactor flow distribution tests had been conducted in order to determine the hydraulic characteristics of the APR+ (Advanced Power Reactor Plus) which were used as the input data for the open core thermal margin analysis code. In this study, in order to examine the applicability of computational fluid dynamics with the porous model in the analysis of reactor internal flow, simulation was conducted with the commercial multi-purpose computational fluid dynamics software, ANSYS CFX V.14. In addition, among the various reactor internals the effect of flow skirt geometry on reactor internal flow was investigated. It was concluded that depending on the shape of flow skirt the flow distribution was locally somewhat different. Standard deviation of mass flow rate (σ) for the original shape of flow skirt was smaller than that for the modified shape of flow skirt. This means that the original shape of flow skirt may give the more uniform distribution of mass flow rate at core inlet plane, which may be more desirable for the core cooling. Porous model for some reactor internal structures could adequately predict the hydraulic characteristics inside reactor in a qualitative manner. However, while the predicted high core inlet flow rate region was located in the core center zone, the measured one was located in the core outer boundary. This difference may result from the fact that some internal structures including the lower support structure assembly were not modeled with the real geometry but treated as the porous domain. If the sufficient computation resource is available, the predicted core inlet mass flow distribution is expected to be more accurate by considering the real geometry of the internal structures, especially located in the upstream of core inlet.