Patent Number: 
Section: claims

1. An elongated nuclear fuel assembly including:a top nozzle;a bottom nozzle;a plurality of fuel rods respectively situated between below the top nozzle and above the bottom nozzle; andan axis along an elongated dimension extending from the top nozzle to the bottom nozzle; andwherein the bottom nozzle comprises:a multi-sided face having sides extending in the axial direction and around the circumference of the bottom nozzle,a circular, tubular mounting at a lower end of the bottom nozzle, anda transition region between the multi-sided face and the bottom nozzle, wherein the transition region has a frustoconical shape having a plurality of flat taper regions formed therein, each flat taper region corresponding to one side of the multi-sided face such that each flat taper region directly adjoins its corresponding side of the multi-sided face and edges of each flat taper region are aligned with edges of its corresponding side of the multi-sided face where each flat taper region adjoins its corresponding side of the multi-sided face,wherein, outside of the flat taper regions, the transition region linearly transitions in radius from a radius of the multi-sided face to a radius of the circular, tubular mounting,wherein the flat taper regions extend approximately half of a height of the transition region,wherein each of the flat taper regions extends at an angle between 5-15 degrees relative to its corresponding side of the multi-sided face. 2. The nuclear fuel assembly of claim 1 wherein the multi-sided face has more than four sides. 3. The nuclear fuel assembly of claim 2 wherein the bottom nozzle has a hex face. 4. The nuclear fuel assembly of claim 1 wherein the sides of the multi-sided face are substantially parallel to the axis of the fuel assembly. 5. The nuclear fuel assembly of claim 1 wherein each of the flat taper regions extends at an angle between 8-12 degrees relative to its corresponding side of the multi-sided face. 6. The nuclear fuel assembly of claim 1 wherein each of the flat taper regions extends from its corresponding side of the multi-sided face.