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.