Patent Number: 047818859
Section: claims

1. Nuclear reactor fuel assembly, comprising a fuel assembly top fitting having a square cross section, a fuel assembly base having a square cross section, an elongated fuel channel with a square cross section and channel walls, fuel rods containing nuclear fuel and an elongated prismatic water channel box both being disposed in said fuel channel in a spacing configuration defined by a lattice having mesh openings with sides parallel to said channel walls, said fuel rods being mutually spaced apart in said mesh openings, said water channel box having a cross section spanning more than one of said mesh openings, and said water channel box being spaced apart from said fuel channel by an interspace being completely filled with said mesh openings and said fuel rods disposed therein. 2. Nuclear reactor fuel assembly according to claim 1, wherein said water pipe is centrally disposed in said lattice. 3. Nuclear reactor fuel assembly according to claim 1, wherein said cross section of said water channel box is square. 4. Nuclear reactor fuel assembly according to claim 2, wherein said cross-section of said fuel channel has cross-section sides, said cross-section of said water channel box is square and has cross-sectional sides, said cross-sectional sides of said water channel box are each parallel to a respective cross-sectional side of said fuel channel, and said cross-sectional sides of said water channel box are each spaced apart from a respective one of said cross-sectional sides of said fuel channel by the same distance. 5. Nuclear reactor assembly according to claim 4, wherein said lattice has n.times.n mesh openings, where n.gtoreq.8, said cross section of said central water channel box spanning (n-6).times.(n-6) mesh openings leaving remaining mesh openings between said water channel box and said fuel channel being occupied solely by fuel rods. 6. Nuclear reactor fuel assembly, comprising an elongated fuel channel with a square cross section, fuel rods containing nuclear fuel being mutually spaced apart in an array in said fuel channel, each of said fuel rods being surrounded by a space with a substantially equal volume, and a prismatic water channel box having a cross section spanning more than one of said spaces, said water channel box and said fuel channel being mutually spaced apart defining a region therebetween being completely filled with said spaces and said fuel rods disposed therein.