VVER-1000 fuel assembly bottom nozzle
A VVER-1000 nuclear fuel assembly having a modified bottom nozzle with chamfers at the upper edge of the frustoconical transition from a hexagonal upper section of the nozzle to the lower circular end that mounts on a lower core support.
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; and
an axis along an elongated dimension extending from the top nozzle to the bottom nozzle; and
wherein 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, and
a 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.