Fluctuating pressure measurements induced by flow through mixing grid
Conference Paper
Overview
Identity
Additional Document Info
View All
Overview
abstract
Nuclear fuel assembly design innovations are regularly incorporated into existing designs in order to achieve higher safety, performance and flexibility. The parameters of importance associated with a particular fuel design are obtained by traditional calculations, experimentation and an extensive certification process. Advancements in analytical methods have occurred since the late 1990's to improve the prediction of the local thermal-hydraulic conditions in fuel assemblies. One method utilized in Pressurized Water Reactor (PWR) fuel is the use of Computational Fluid Dynamics (CFD) to predict the temperature, flow structure, flow rate and flow behavior downstream of grids with mixing vanes. The CFD simulations are aimed to forecast the fuel behavior under various scenarios in order to draw lines regarding fuel integrity under all operating conditions. Flow-induced vibrations of fuel rods generating grid-to-rod fretting are the dominant fuel leakeing mechanism worldwide. Benchmarking of the CFD models has been performed with the available data to provide a reasonable prediction. As advancements in both computational speed and data acquisition methods have improved dramatically over recent years, there is an opportunity to further improve the CFD model methodology and provide closer predictions to PWR conditions. This paper discusses the advanced hydraulic data obtained on Westinghouse PWR mixing vane grids at Texas A&M University. The data acquisition of interest is from a Laser Doppler Velocimetry (LDV) and rod-mounted miniature pressure sensors (RMPS) technique which can get local instantaneous pressure-velocity correlation and the pressure rod-wall power spectra. The power spectra from the miniature sensors show the shift in frequencies as a function of axial distance from the mixing-vanes. The quality of the data represents a step-change improvement from the prior data used to benchmark the CFD methodology.
