Patent Number: 
Section: claims

1. A method of manufacturing a fuel assembly for use in a core of a nuclear power reactor, the method comprising:manufacturing each of a plurality of elongated fuel elements by:mixing powdered fuel material with powdered metal non-fuel material, wherein the powdered fuel material comprises fissile material,sintering the mixed powdered fuel material and metal non-fuel material to create a fuel core stock,surrounding the fuel core stock with a cladding material, andco-extruding the fuel core stock and cladding material to create the fuel element, the fuel element having a spirally twisted, multi-lobed profile that defines a plurality of spiral ribs, the multi-lobed profile comprising lobe tips and intersections between adjacent lobes, the cladding being thicker at the tips than at the intersections; andmounting the plurality of elongated fuel elements to a frame of the fuel assembly,wherein a moderator:fuel ratio in a region of the fuel elements defined by a shroud of the fuel assembly is 2.5 or less. 2. The method of claim 1, wherein:the plurality of elongated fuel elements comprise a plurality of elongated metal fuel elements; andthe powdered fuel material comprises powdered metal fuel material; andthe fuel core stock comprises a metal fuel core stock comprising an alloy of the metal fuel material and the metal non-fuel material. 3. The method of claim 1, wherein the powdered fuel material comprises powdered ceramic fuel material. 4. The method of claim 1, wherein the plurality of elongated fuel elements provide at least 60% by volume of the overall fissile material of the fuel assembly. 5. The method of claim 1, wherein an average thickness of the cladding after co-extrusion is at least 0.6 mm. 6. The method of claim 1, further comprising positioning a displacer within the mixed powdered fuel material and metal non-fuel material before said sintering such that said sintering results in a fuel core stock that includes the displacer. 7. The method of claim 1, wherein:the frame comprises a lower nozzle that is shaped and configured to mount to a core of a land-based nuclear power reactor; andthe fuel assembly is thermodynamically designed and physically shaped for operation in the land-based nuclear power reactor. 8. The method of claim 7, further comprising placing the fuel assembly into the land-based nuclear power reactor.