Patent Number: 061447161
Section: claims

1. A nuclear fuel assembly having a support grid for maintaining a plurality of elongated nuclear fuel elements in a parallel, spaced array, the grid having a lattice structure which defines a plurality of cells through which the fuel elements are respectively supported, each of the cells having a plurality of walls which intersect at corners and surround the corresponding fuel element at the support location, at least one wall in the cells supporting the fuel elements includes a diagonal spring extending into the cell from a point near a lower portion of the grid proximate one corner of the wall to a point near an upper portion of the grid proximate the other corner of the wall, and wherein the spring is formed from a cut-out section of the cell wall formed from narrow, substantially parallel slits in the wall along the diagonal of the spring in a manner that minimizes the cross flow of coolant between cells at the spring location during reactor operation. 2. The nuclear fuel assembly of claim 1 wherein the walls of the cells are formed from an intersection of lattice straps where one of the intersecting straps has a slit extending from its upper end along the line of intersection and the other intersecting lattice strap has a slit extending from its lower end along the line of intersection, wherein the slits intersect and fit over each other in an egg-crate configuration and each slit extends over more that half the height of the corresponding lattice strap so as to soften the force of the springs against the fuel elements. 3. The nuclear fuel assembly of claim 2 wherein the straps are welded together at their lines of intersection so that their corresponding adjoining edges are substantially aligned. 4. The nuclear fuel assembly of claim 2 wherein the ends of the abutting slits of intersecting straps are spaced from one another. 5. The nuclear fuel assembly of claim 1 wherein the support grid spring is attached to the cell wall along a vertical line parallel to the intersection of cells walls, wherein the restriction to coolant flow at any point along the spring is limited to the thickness of the spring material. 6. The nuclear fuel assembly of claim 1 wherein the diagonal slits in the cell walls which form the spring terminate at either end in slits in the cell walls running substantially parallel to the adjacent walls in a direction away from the spring. 7. The nuclear fuel assembly of claim 1 wherein the diagonal spring has a chamfer along at least a portion of one edge. 8. A nuclear fuel assembly having a support grid for maintaining a plurality of elongated fuel elements in a parallel, spaced array, the grid having a lattice structure which defines a plurality of cells through which the fuel elements are respectively supported, each of the cells having a plurality of walls which intersect at corners and surround the corresponding fuel element at the support location, at least one wall in the cells supporting the fuel elements includes a spring for supporting the fuel element, the spring is formed from two parallel slits in the cell wall, where the slits run on an angle to the line of intersection of the cell walls and terminate at each end in a slit that runs parallel to the line of intersection in a direction away from the spring. 9. The fuel assembly of claim 8 where the parallel slits that form the spring are at forty five degree angle with the line of intersection of the cell walls.