Patent ID: 7469030

Claim:
A nuclear fuel element comprising a bundle of fuel rods and a framework for holding the bundle, wherein each of the fuel rods are of substantially cylindrical shape, and said framework comprises a plurality of spacer grids for a fuel assembly in a light-water-cooled nuclear reactor, for providing a transverse retention of the bundle of fuel rods in mutually parallel arrangements, at least one of the plurality of spacer grids comprising: an array of cells juxtaposed and placed in a regular lattice, each bounded and separated from neighboring cells by at least one peripheral wall which is open at two opposed ends, along a direction of an axis of the cell, the axis being vertical, so as to receive one of the fuel rods, said one of the fuel rods passing along the cell axis parallel to the peripheral wall, and an arrangement for bearing on and retaining the one of the fuel rods in a central position in which an axis of the one of the fuel rods lies along the axis of the cell, a free space being left between a cylindrical external surface of the one of the fuel rods and the peripheral wall of the cell, in which the arrangement for bearing on and retaining the one of the fuel rods in each of the cells housing a fuel rod comprises a wall having a form of a helical sheet extending transversely in the free space between the external surface of the one of the fuel rods and the peripheral wall of the cell so as to bear on the one of the fuel rods over a substantial part of the height of the cell in a direction of the axis of the cell, wherein the wall having a form of a helical sheet comprises at least one element in a helical arrangement with respect to the axis of the cell, wherein the at least one element in a helical arrangement consists of a part of the peripheral wall of the cell cut in the peripheral wall along a direction inclined to the axis of the cell and folded so as to constitute a blade-shaped first part of direction transverse to the peripheral wall and a second part folded with respect to the first part, the second part extending approximately parallel to the peripheral wall and constituting a bearing surface for the external surface of the one of the fuel rods, wherein the second part is joined to the peripheral wall of the cell via the transverse first part constituting a spring leaf retaining the one of the fuel rods and for guiding a cooling fluid in a helical arrangement with respect to the axis of the cell, and wherein the second part folded with respect to the first part bears on the one of the fuel rods over a part of the height of the cell in the direction of the axis of the cell.