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Numerical simulation on a HPLWR fuel assembly flow with one revolution of wrapped wire spacers

Numerische Berechnung der Strömung im HPLWR Brennelement beim Einsatz von Brennstäben mit Drahtabstandshaltern
A. Kiss, E. Laurien, A. Aszódi and Y. Zhu
From the journal Kerntechnik

Abstract

Three dimensional computational-fluid-dynamics simulations are performed for the fluid flow within a 40 rod fuel bundle in a square arrangement with a central moderator channel. To ensure spacing between the rods, the design of the bundle uses thin wires wrapped counter-clockwise around each rod. This geometry is presently investigated in the framework of the European High-Performance Light-Water Reactor (HPLWR), which operates at supercritical pressure of 25 MPa. A section with one revolution located in the evaporator region of the HPLWR core is investigated using hydraulic (to ensure fully developed flow inlet boundary conditions and reference for heated cases) and thermal-hydraulic boundary conditions. The geometry of wrapped wires gives rise to additional mixing and a circulating or ‘sweeping’ flow near the outer and inner regions of the fuel element next to the wall of the so called fuel assembly and moderator box. Some interesting flow features associated with the complex three-dimensional flow with significant transverse velocity components are visualized as the first evaluated result of this diversified investigation.

Kurzfassung

Für ein Brennelement des European High-Performance Light-Water Reactors (HPLWR), der bei überkri-tischen Drücken von 25 MPa betrieben werden soll, wird eine Analyse der Kühlmittelströmung im Brennelement mit dem 3D-Computational Fluid Dynamics (CFD) Programm CFX-11 durchgeführt. Das Brennelement ist quadratisch aufgebaut und besteht aus einem zentralen Moderatorkanal und 40 Brennstäben. Die Abstandshalter bestehen aus dünnen Drähten, die gegen den Uhrzeigersinn um jeden Brennstab gewickelt sind. In den Berechnungen wird der Bereich einer Umwicklung des Abstandshalters in dem so genannten Verdampfer-Kernbereich im Detail untersucht unter Berücksichtigung hydraulischer und thermohydraulischer Randbedingungen. Diese sind so gewählt, dass als Randbedingung eine vollständig entwickelte Strömung im Eintritt vorliegt und dass diese als Referenz für die verschiedenen Randbedingungen bzgl. der Temperaturverteilungen dienen. Die Geometrie der gewickelten Drähte führt zu einer zusätzlichen Vermischung und ”Mitriss“-Strömung in der Nähe der äußeren und inneren Regionen des Brennelements, das sich in Wandnähe der Brennelementumwandung und Moderatorbox befindet. Einige interessante Strömungseigenschaften der komplexen 3D-Strömung mit signifikanten Queranteilen der Geschwindigkeit werden als erste Ergebnisse dieser Untersuchungen vorgestellt.


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Received: 2010-1-11
Published Online: 2013-04-05
Published in Print: 2010-08-01

© 2010, Carl Hanser Verlag, München