Nuclear reactor (alternatives), fuel assembly of seed-blanket subassemblies for nuclear reactor (alternatives), and fuel element for fuel assembly

A fuel assembly for use in a nuclear reactor, the fuel assembly comprising:

• a frame configured to be removably disposed in a nuclear reactor;
• and
• a plurality of fuel elements supported by the frame,
• wherein at least some of the plurality of fuel elements each comprise:
• a kernel having a multi-lobed profile that forms spiral ribs that comprise fissionable material,
• a central metal displacer extending along a longitudinal axis of the kernel, and
• a metal cladding enclosing the kernel,
• wherein the at least some of the plurality of fuel elements are each fabricated by joint extrusion of the displacer, kernel, and cladding through a die.

A method of manufacturing a fuel element for use in a nuclear reactor, the method comprising:

• joint extruding a kernel, a central metal displacer, and a cladding through a die to form the fuel element,
• wherein, after said extruding, the kernel has a multi-lobed profile that forms spiral ribs that comprise fissionable material;
• wherein, after said extruding, the displacer extends along a longitudinal axis of the kernel;
• and
• wherein, after said extruding, the metal cladding encloses the kernel,
• wherein, after said extruding, the spiral ribs have a pitch of axial twist of between 5% and 20% of a length of the fuel element.