Non-Intrusive SPIV of Flow Behavior Inside a 5x5 Rod Bundle with Spacer Grids

Abstract

New and improved thermal hydraulic data is essential for ensuring safe operation for Pressurized Water Reactors (PWR). Excessive fission product buildup on fuel rods produces uneven subcooling during operation which poses safety risks. Local sub-channel and fuel rod conditions are key parameters of interest in order to establish accurate critical heat flux parameters. Computational Fluid Dynamics (CFD) calculations are needed to produce these parameters but are very challenging due to the complex nature of two-phase and flow field in a PWR. CFD calculations rely on development of improved complex flow simulations with reasonably detailed flow structures with dynamic interaction of the flow. Having a better understanding of flow behavior in these geometries directly translates to the safety of nuclear power plants. To validate and benchmark contemporary CFD calculations, a scale modeled test facility was built. Experimental measurements were taken inside a 5x5 rod bundle with spacer grids to help validate current CFD codes. A non-intrusive approach was taken using Stereoscopic PIV (SPIV) techniques along with a Matching Index of Refraction (MIR) optical approach. This paper presents SPIV and pressure analyses on an existing Westinghouse 5x5 Spacer Grid facility.