Patent ID: 7085340
Filing Date: 2006-08-01
Classification: G21C,Y02E

Abstract:
1. A nuclear fuel assembly comprising: A parallel array of elongated nuclear fuel elements supported between a lower nozzle and an upper nozzle and having an axial length along the elongated dimension of the nuclear fuel elements with a mid third region along the axial length; A plurality of substantially evenly spaced main support grids arranged in tandem along the axial length of the fuel elements, between the upper nozzle and the lower nozzle, at least partially enclosing an axial portion of the circumference of each fuel element within a support cell of the main support grids, with each support cell supporting only a single fuel element, to maintain a lateral spacing between fuel elements; and At least one auxiliary grid positioned around the fuel elements in tandem with the main support grids at an elevation in the mid third region, the auxiliary grid comprising a plurality of support cells with one support cell for each fuel element, with each support cell supporting only a single fuel element, wherein the auxiliary grid is supported between two main support grids without any other auxiliary grids between the auxiliary grid and the adjacent main support grid and wherein the main support grids have a first fuel element support assembly and the auxiliary grid has a second fuel element support assembly and the first and second fuel element support assemblies are of a different design; and wherein the auxiliary grid support cells have walls that respectively at least partially enclose a portion of the circumference of the fuel elements along a portion of their axial length and the second fuel element support assembly is located on the walls of the auxiliary grid support cells and comprise a second set of dimples and/or springs that continuously contact and support the fuel elements and the main support grids' cells have walls that respectively at least partially enclose a portion of the circumference of the fuel elements along a portion of their axial length and the first fuel element support assembly is located on the walls of the main support grids' cells and comprise a first set of dimples and/or springs that continuously contact and support the fuel elements, wherein the second set of dimples and/or springs on the auxiliary support cells have a larger contact area with the fuel elements than the first set of dimples and/or springs on the walls of the main support grid cells.