Westinghouse Electric Company LLC

Westinghouse Electric Corporation

Yu Chung Lee

James A Sparrow

Peter H Beuchel

Levie David Smith, Iii

Yonghwan Kim

Edmund E DeMario

David L Stucker

Joonhyung Choi

Quang M Nguyen

Jin Liu

Michael G Smith

Kyouseok Lee

Jeffrey J Fodi

Darin L Redinger

A nuclear fuel assembly having a plurality of multi-leaf hold down spring sets extending from a top nozzle. Each spring set consists of a multiple number of springs leafs in order to provide a large working range of spring deflection. Each spring leaf has a straight, flat base section followed by a straight, flat tapered beam with a secondary spring set having a curvature at its peripheral end.

Nuclear fuel assembly hold down spring

A plate mounted fuel assembly hold-down system that provides a defined channel for both the insertion and removal of reactor head mounted, fixed in-core detector instrumentation, provides a guided path for the fixed in-core detector during insertion, and shields the instrument shroud against coolant cross flow. The hold-down assembly includes a base plate that seats on the adapter plate of the fuel assembly and has openings that align with the control rod guide thimbles. A hollow sleeve extends through and below a central opening in the base plate to mate with the fuel assembly instrument thimble. The sleeve extends above the base plate and through and above an upper core plate of the reactor. A hold-down bar is slidably mounted on the sleeve and is restrained below the top of the sleeve. A spring is positioned around the sleeve and is captured between the hold-down bar and the base plate.

Nuclear core component hold-down assembly

An integral multilevel debris-catching system for a nuclear reactor fuel assembly having a lower protective grid incorporating laterally offset debris-catching arches at several elevations, extended solid fuel rod bottom end plugs and a bottom debris-filtering nozzle. Dimples and opposing opposite springs and the debris-trapping arches, which are spaced from the end plugs, are all located at elevations below the fuel cladding.

Nuclear fuel assembly protective grid

A reduced pressure drop debris filter bottom nozzle for use in a fuel assembly of a nuclear reactor includes a plate member formed with a plurality of first flow holes and a plurality of second flow holes. The first flow holes are oblong in cross section and may be of an oval configuration. The first flow holes each have in cross section a major axis and a minor axis, the major axis being longer than the minor axis. The second flow holes are circular in cross section and may have a diameter substantially equal to the minor axis of the first flow holes. The bottom nozzle also features support ligaments that extend between the first flow holes and that are axially aligned with fuel rods within the fuel assembly.

Reduced pressure drop debris filter bottom nozzle for a fuel assembly of a nuclear reactor

An improved grid for use in a fuel assembly of a nuclear reactor includes a plurality of straps connected in a lattice, with a plurality of mixing vanes being disposed on the straps and being arranged such that the hydraulic forces on the mixing vanes generally cancel one another out. The mixing vanes of diagonal quadrants of the grid are generally aligned with diagonally disposed imaginary alignment planes. Each strap includes a plurality of strap members, with each strap member including a spring and a pair of dimples. The spring includes a contoured spring embossment having a greater radius of curvature in a relaxed condition than the radius of a fuel rod. Each dimple includes a similarly configured contoured dimple embossment. The spring embossment is mounted on a pair of legs that extend nonlinearly between a first plate and a second plate of each strap member to increase compliance thereof.

Nuclear reactor with improved grid

A support grid for laterally maintaining the relative position of elongated fuel elements within a fuel assembly for use within a core of a nuclear reactor. The grid is formed in the shape of a lattice with the intersecting lattice members defining a plurality of cells, most of which respectively support the nuclear fuel elements. The remaining cells support nuclear control rod guide tubes and instrumentation thimbles. The cells supporting the nuclear fuel elements are provided with diagonally positioned springs on two, adjacent walls. The springs support the fuel elements against dimples which protrude from the opposite cell walls. The adjacent, diagonal springs in each fuel element cell are inclined in opposite directions. The walls of the cells supporting the control rod guide tubes are embossed along their height at the locations intermediate the intersection between adjoining walls with a concave notch having a curvature which conforms to the outside surface curvature of the control rod guide tubes. The grid is provided with mixing vanes which are positioned in a symmetrical, regional pattern, with the pattern varying between adjacent regions, and configured such that the hydraulic forces across the center of the grid are balanced. The grid is reinforced with welds at the mid point of the intersection of the lattice straps.

Nuclear fuel assembly with hydraulically balanced mixing vanes

Disclosed is a grid structure for supporting fuel rods in a nuclear reactor. The grid structure is formed of a plurality of interconnected thin metal grid straps that are welded or brazed together to provide a structural network of interconnected open grid cells, similar to an 'egg crate divider'. The grid straps are provided at regular intervals, corresponding to the width of a grid cell, with pairs of spaced, substantially horizontal, slotted spring-like projections and a substantially X-shaped spring-like projection vertically intermediate the horizontal projections. The spring-like projections are designed to support and hold the fuel rods within the grid cells under both balanced and unbalanced forces acting on the fuel rod assembly while it is in service, surrounded by coolant in the nuclear reactor.

Grid structure for supporting fuel rods in a nuclear reactor

An expandable top nozzle subassembly for a nuclear fuel assembly includes an upper structure having a top plate and a depending peripheral sidewall enclosure, a lower adapter plate disposed below the top plate and within the enclosure with the adapter plate and sidewall enclosure being slidably movable relative to one another so as to move the top plate toward and away from adapter plate, and a plurality of resiliently-yieldable biasing devices extending between and engaging the top plate and lower adapter plate. Interengagable structure on a lower edge of the enclosure and on a peripheral edge of the adapter plate capture and retain the adapter plate within the enclosure upon movement of the enclosure relative to the adapter plate which moves the top plate away from the adapter plate. The biasing devices in the form of coil springs are movable between compressed and expanded states in response respectively to application and removal of a hold-down force on the upper structure in the direction of the adapter plate for permitting and causing movement of the enclosure relative to the adapter plate so as to move the top plate toward and away from the adapter plate and thereby the top nozzle subassembly between compressed and expanded conditions.

Nuclear fuel assembly with expandable top nozzle subassembly

A fuel pellet for a nuclear reactor fuel rod is fabricated with smooth and gently sloping surfaces having no sharp edges or areas of high stress concentration. The bearing surfaces of the fuel pellets are contoured so that the pellets are easily stacked within a fuel rod and permit pivoting action between the fuel pellets. The fuel pellets are stacked end to end in a fuel rod which is incorporated into a fuel assembly for a nuclear reactor.

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Columbia, SC, United States of America

Yu Chung Lee