Patent Number: 042749212
Section: claims

1. Fuel assembly for gas-cooled fast breeder nuclear reactors comprising a cluster of parallel-disposed fuel rods, and a steel casing surrounding said cluster of parallel-disposed fuel rods and defining a coolant flow configuration, the fuel rods being disposed in a manner that the axes thereof intersect imaginary coaxial circles, said casing being of circular cylindrical shape having a wall of lesser thickness than that of an hexagonal fuel-assembly casing of equal strength under like pressure and temperature stresses, so that the resultant increase in nuclear core volume of an assembly of a plurality of said circular-cylindrical fuel-assembly casings over the nuclear core volume of an assembly of hexagonal fuel-assembly casings due to a presence of wedge-shaped spaces between the circular-cylindrical fuel-assembly casings is at most equal to a consequent reduction in nuclear core volume due to a reduction in the amount of steel of the less thicker walls of the circular-cylindrical fuel-assembly casings. 2. Fuel assembly according to claim 1 comprising coolant subchannels extending in the middle of the cluster and being bordered by fuel rods of reduced output having a lower enrichment than the remaining fuel rods of the fuel assembly. 3. Fuel assembly according to claim 1 including a central guide tube disposed coaxially to the casing, and a breedermaterial element received in the interior of said central guide tube. 4. Fuel assembly according to claim 1 including a central guide tube disposed coaxially to the casing, and a control element formed of absorber material axially adjustably disposed in the interior of said central guide tube. 5. Fuel assembly according to claim 1 including coolant subchannels extending in the middle of the cluster concentrically to said circular-cylindrical casing and comprised of cylindrical guide tubes.