Patent Number: 061513768
Section: claims

1. A fuel assembly for a light-water reactor with a substantially square cross section comprising a plurality of fuel rods extending between a top tie plate and a bottom tie plate, wherein a coolant is adapted to flow from below and up through the fuel assembly and a fuel rod comprises a cladding tube which surrounds a column of fissionable material wherein at least one fuel rod is provided with an axial gap in the fissionable material and wherein a thickness of a unitary material around the axial gap is greater than a thickness of a material in a main part of the cladding tube. 2. A fuel assembly according to claim 1, wherein the axial gap is arranged in the upper part of the fuel rod. 3. A fuel assembly according to claim 1, wherein the axial gap is arranged surrounded by a top plug adapted to seal the upper end of the cladding tube and wherein the greater thickness is arranged in the top plug. 4. A fuel assembly according to claim 1, wherein a diameter of the axial gap corresponds to an inner diameter of the main part of the cladding tube. 5. A fuel assembly according to claim 1, comprising a plurality of fuel units, each comprising said plurality of fuel rods, wherein an axial extent of said axial gap is dependent on a length of said fuel rods. 6. A fuel assembly according to claim 1, wherein said unitary material is metallurgically homogeneous. 7. A fuel assembly according to claim 1, wherein a portion of said unitary material is formed into mixing vanes or flanges. 8. A fuel assembly according to claim 7, wherein said mixing vanes are formed as bars extending out from the outwardly-facing surface of the material and are disposed at an angle .alpha. in relation to a center axis of said cladding tube.