Method of manufacturing a nuclear fuel assembly

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, and
• co-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;
• and
• mounting 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.