Westinghouse Electric Company LLC

Westinghouse Electric Corporation

Quang M Nguyen

Edmund E DeMario

Lewis A Walton

Paul M Evans

Radu O Pomirleanu

Yu Chung Lee

Mark P Goldenfield

Raymond W Brashier

Levie David Smith, Iii

Michael Anthony Marzean

Abdelaziz M Elmahdi

Virgil Jamie Vasquez

Jeffrey J Fodi

Darin L Redinger

John C Rue, Jr

Gregory E Settle

Gregory D Livermore

A bi-alloy spacer grid (BASG) is provided with grid straps and springs made using different zirconium alloys. The grid straps are made from a relatively low growth zirconium alloy, and the springs are made from a relatively high growth zirconium alloy. The springs are coupled to the grid straps by welding, mechanical interference, or secondary forming in place. When subjected to irradiation, the springs grow relative to the grid straps thereby maintaining contact with the fuel rod cladding, while the grid straps resist growth to maintain structural stability of the entire fuel assembly. The optimized balance of the high growth springs and low growth grid straps mitigates the formation of gaps between the fuel rods and grid support structures). The growth properties of the grid straps and springs may be further controlled through optional different fabrication processes.

Bi-alloy spacer grid and associated methods

A nuclear fuel assembly having a parallel array of elongated fuel elements supported between an upper and lower nozzle. Main support grids are substantially evenly spaced along the elongated dimension of the assembly to maintain the spacing between fuel elements. A plurality of auxiliary vibration-resistant grids respectively positioned between the main support grids in the middle third elongated dimension of the fuel elements, that are smaller in height and provide a larger fuel element contact area than the main support grids.

Nuclear reactor fuel assemblies

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

A new spring design for a strap employed in a grid of a nuclear reactor fuel assembly includes a pair of ligaments that each connect with the free portion of the retention plate. The ligaments each are equally spaced a certain distant from the termination of the slots within the strap body. The spring additionally includes a spring contact plate that is wider than the connections of the spring ligaments with the free portion to increase the surface area with which the spring contact plate is in contact with and retains the fuel rod, and thus reduces the contact stresses therebetween. The spring contact plate additionally includes an embossed spring contact member protruding outwardly therefrom reduces the frictional stresses on the fuel rod when it is inserted into and removed from the cell and during vibration of the fuel rod and/or the strap.

Fretting resistant spring design

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 springs are formed from narrow, parallel slits in the cell wall that terminate along a line parallel to the line of intersection with the adjacent wall. The spring slits continue along that parallel line in a direction away from the spring to increase its flexure. The lattice is formed in an 'egg-crate' pattern with the orthogonal members fitting over opposing vertical slits in the adjoining straps. The vertical slits are extended more than half way over the width of the straps to further increase the flexure of the retaining springs.

Nuclear fuel assembly grid with diagonal fuel retaining springs

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Export, PA, United States of America

Quang M Nguyen