Apparatus for supporting radioactive fuel assemblies, such as spent nuclear fuel. In one aspect, the invention is an apparatus, which can be in the form of a fuel basket, fuel rack, or the like, in which hexagonal storage tubes are used not only for their internal cells but are also strategically patterned to create resultant cells with their outside surfaces. In another aspect, the invention is an apparatus having flux traps surrounding each cell wherein the size of the flux traps decrease with distance from the center of the storage grid.