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CFD Model for Inlet Flow Region of 17×17 Fuel Assembly |
Milorad B. Dzodzo, Bin Liu, Pablo R. Rubiolo, Zeses E. Karoutas,
Michael Y. Young
Science and Technology Department, Westinghouse Electric Company LLC
A numerical investigation was performed to study the variation in axial and lateral velocity profiles occurring downstream of the inlet nozzle of a typical Westinghouse 17×17 pressurized water reactor (PWR) fuel assembly. A Computational Fluid Dynamic (CFD) model was developed with commercial CFD software. The model comprised the lower region of the fuel assembly, including: the Debris Filter Bottom Nozzle (DFBN), P-grid, Bottom Inconel grid, one and half grid span, as well as the lower core plate hole. To be able to provide the converged solution and due to the very complex geometry, two different meshing approaches were used for the upper and lower portions of the domain.
The purpose of the study was to obtain insight into the flow redistribution resulting from the interaction of the jet arising from the lower core plate hole and the fuel assembly structure. In particular the axial and lateral velocities before and after the nozzle were studied.
The results, axial and lateral velocity contours, streamlines and maximum axial and lateral velocity distributions at various elevations are presented. The CFD model results indicated that the large jet flows from the lower core plate are effectively dissipated by DFBN nozzle and the grids components of the fuel assembly. The breakup of the large jets in the DFBN and the lower grids helps to reduce the steep velocity gradients and thus the rod vibration and fretting-wear risk in the lower part of the fuel assembly.
The presented CFD model is one step towards developing advanced tools that can be used to confirm and evaluate the effect of complex PWR structures on flow distribution involving several fuel assemblies.
Contact
Dr. Milorad B. Dzodzo
Fellow Engineer
Thermal, Fluid & Nuclear Engineering
Science and Technology Department
Westinghouse Electric Company
1344 Beulah Road
Pittsburgh, PA 15235, USA
dzodzomb@westinghouse.com