Patent Number: 048270636
Section: claims

1. Nuclear reactor fuel assembly, comprising mutually parallel fuel rods and guide tubes for control rods, two lattice-like spacers having mesh openings formed therein, one of said fuel rods or one of said guide tubes being guided and secured in each of said mesh openings, an additional lattice secured at least to one of said guide tubes between said two spacers as seen in the longitudinal direction of said fuel rods and said guide tubes, said additional lattice having mesh openings formed therein defining sides of said mesh openings and a smooth and flat surface of said additional lattice in said mesh openings, turbulence-promoting vanes protruding beyond said sides of said mesh openings formed in said additional lattice, one of said fuel rods being guided with play or one of said guide tubes being guided through each of said mesh openings formed in said additional lattice, and brackets gripping said additional lattice between at least one of said fuel rods or said guide tubes at the outside of the fuel assembly, the mesh openings of the additional lattice, disposed at the outside of the lattice, being open in direction facing away from the fuel assembly. 2. Fuel assembly according to claim 1, wherein said additional lattice has mutually parallel edges with zig-zag portions, each of said zig-zag portions being compactly disposed in the plane of one of said sides of one of said mesh openings formed in said additional lattice. 3. Fuel assembly according to claim 1, wherein said mutually parallel edges are leading and trailing edges. 4. Fuel assembly according to claim 2, wherein said zig-zag portions of said edges are mutually staggered. 5. Fuel assembly according to claim 3, wherein said zig-zag portions of said edges are mutually staggered. 6. Fuel assembly according to claim 1, wherein said additional lattice is spaced apart from said two first-mentioned spacers by unequal distances. 7. Fuel assembly according to claim 1, wherein said additional lattice has mutually parallel edges on which said turbulence-promoting vanes are disposed, each of said edges having ends and being associated with one of said sides of said additional lattice, each two adjacent turbulence-promoting vanes on one of said mutually parallel edges of said additional lattice being: twisted in mutually opposite directions about the longitudinal direction of said fuel rods and said guide tubes,  located on one of said edges of one of said mesh openings of said additional lattice for a fuel rod, and  tapered to a point and protruding beyond said side of said mesh opening associated with said edge at one of said ends of said edge. 8. Fuel assembly according to claim 7, wherein said mutually parallel edges are leading and trailing edges.