Optimized flower tubes and optimized advanced grid configurations

Abstract

A support grid for a nuclear fuel assembly, the fuel rod assembly having a generally cylindrical fuel rod with a diameter, wherein the support grid includes a frame assembly having a plurality of outer straps and a plurality tubular members and / or helical frame members. The tubular members / helical frame members have a contact portion structured to contact an adjacent helical frame member and at least one helical fuel rod contact portion with a lesser diameter. The lesser diameter is generally equivalent to the fuel rod diameter such that a fuel rod disposed in the helical frame member would engage the inner helical frame member at helical fuel rod contact portion. The helical fuel rod contact portion may have a variable pitch.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This is a continuation-in-part application claiming priority under 35 U.S.C. §119(e) to U.S. patent application Ser. No. 11 / 033,434, filed Jan. 11, 2005, entitled HELICALLY FLUTED TUBULAR FUEL ROD SUPPORT.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to nuclear reactor fuel assemblies and more particularly to an array for supporting fuel rods wherein the array, or support assembly, consists of a matrix of substantially flat members forming a grid-like frame assembly and a plurality of helically fluted tubular members wherein the helical portions may have a variable pitch.[0004]2. Background Information[0005]In a typical pressurized water reactor (PWR), the reactor core is comprised of a large number of generally vertically, elongated fuel assemblies. The fuel assemblies include a support grid structured to support a plurality of fuel rods. The fuel assembly includes a top nozzle, a bottom noz...

AI Technical Summary

Benefits of technology

[0012]In a preferred embodiment, the tubular member has a wall of uniform thickness so that the helical fuel rod contact portion defines a passage with a helical shape on both the side adjacent to the fuel rod and the side adjacent to the cell wall. These helical shaped passages act to mix the water so that mixing vanes are not required. There are at least two advantages to using the helical shaped passages; first, the water flow does not impinge on the shaped passage, so there is a minimal pressure drop created by the mixing structure. Second, by reversing the direction of the helical passage in selected cells, the amount of torque exerted on the frame assembly may be controlled.

Problems solved by technology

However, given the relatively short height of a typical cell, the pitch (radial distance / height) of the helical fuel rod contact portion may be too great thereby restricting the flow of water through the helical portion of the passage.

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