Abstract: A reusable fastener device includes an attachment nut and a retainer housing mounted to the adapter plate of the fuel assembly top nozzle and removable with the top nozzle upon reconstitution of the fuel assembly. The attachment nut has a central tubular stem and upper and lower flanges connected to and extending radially outwardly from opposite ends of the stem. The stem is internally threaded for mating with the threaded upper end plug extension of the strucutural member. The upper flange of the nut has a conical-shaped lower surface and a periphery adapted for engagement in order to rotate the nut for threading onto and unthreading from the structural member extension between fastened and unfastened positions. The lower flange of the nut is in the form of a plurality of radial segments extending outwardly from the stem and angularly spaced from one another so as to define a plurality of cutouts therebetween which alternate with the segments.

Abstract: A fuel assembly for use at non-control rod locations of a nuclear reactor core includes top and bottom nozzles and longitudinal structural members extending between and attached to the nozzles for forming an integral unitary structure. One or more of the structural members includes an elongated hollow cladding tube extending between the top and bottom nozzles and end plugs secured to opposite ends of the tube for hermetically sealing and attaching the tube to the top and bottom nozzles. The improvements in the structural member relate to features for reducing fuel assembly bow. Such features relate to a quantity of thermal or irradiation-induced creep resistant material and pretensioning means positioned within the tube. The creep resistant material is a ceramic material in stacked pellet form and coated with a burnable adsorber material.

Abstract: A nuclear reactor in which control rods are inserted in the thimbles of only certain of the fuel assemblies (which may be called controlled assemblies) in the core and the remainder of the assemblies (which may be called non-controlled assemblies) are provided with hollow structural members containing burnable poison which form these non-controlled assemblies into integrated units. The hollow structural members are formed with end plugs welded to the lower end and are open at the top. The end plug of each member is secured to the bottom nozzle of the non-controlled fuel assembly. A skeleton is formed of the bottom nozzle, the structural members secured to it and a plurality of grids spaced along the structural members. A bulge tool is then inserted in each hollow member and it is on each side of each grid. Neutron absorbers are then inserted in each hollow member and an upper end plug is welded to it. The fuel rods are then inserted in the assembly and the upper end plugs are secured to the top nozzle.

Abstract: Zirconium alloy or Zircaloy grid straps in a fuel assembly grid have predetermined texture (or grain orientation) to offset stress relaxation which occurs upon irradiation of the grid. Particularly, by providing "f-factor" values of the material greater in generally orthogonal, longitudinal directions of the straps than in the strap height direction, the grid strap material will undergo irradiation shrinkage in the longitudinal directions which will serve to offset stress relaxation and maintain sufficient spring force on the fuel rods extending through the cells formed by the grid straps.

Abstract: The present invention pertains to zirconium base alloys containing about 0.1 to 0.6 weight percent tin; about 0.07 to 0.24 weight percent iron; about 0.05 to 0.15 weight percent chromium; and up to about 0.05 weight percent nickel. The balance of the alloy is zirconium with incidental impurities. The levels of the incidental impurity, oxygen, is controlled to a level of less than about 350 ppm. These alloys have been designed to minimize the adverse effects of pellet-clad interaction, when they are used as a liner bonded to the inside surface of water reactor nuclear fuel cladding. Specific cladding and fuel element designs according to the present invention are described.

Abstract: A hydride blister-resistant nuclear fuel rod cladding has a tubular cladding formed from a zirconium-based alloy which has a thin nickel base film, of a thickness of about 0.01 to 5 microns distributed over between 1-40 percent of the area of the internal surface of the tubular cladding. The dispersed nickel base film provides multiple sites for hydride transport from the interior of the nuclear fuel rod and prevents localized hydride transport and resulting hydride blistering.

Abstract: A trap for catching debris carried by coolant flowing from the bottom nozzle of a fuel assembly to the bottom or lowermost one of the grids of the assembly which support the fuel rods in an organized array therein includes a structure disposed between the bottom nozzle and the bottom grid and generally aligned with the lower end plugs of the fuel rods. The structure forms a multiplicity of hollow cells each being open at opposite ends and defining a central cavity which receives one of the fuel rod lower end plugs while providing for passage of coolant flow therethrough from the bottom nozzle to the bottom grid. Also, the trap includes means in the form of dimples defined in each of the cells for catching debris carried into the cells by the coolant flowing therethrough. The dimples are formed from the wall portions defining the cells and extend into the cavities of the cells.

Abstract: A nuclear reactor component such as a fuel rod, burnable absorber rod, or neutron absorber rod, comprising a hermetically sealed metallic tube containing a solid material such as a nuclear fuel, burnable absorber, or neutron absorber, within a helium atmosphere, which solid material will release tritium into the helium atmosphere, has added thereto about 2-3 percent by volume of a gas, selected from oxygen, carbon monoxide and carbon dioxide. The addition of this gas to the helium atmosphere is effective to form an oxide layer on the inner surface of the metallic tube and significantly reduce the permeation of tritium through the metallic tube, such that the tritium is retained within the reactor component.

Abstract: An open lattice elongated nuclear fuel assembly including small diameter fuel rods disposed in an array spaced a selected distance above an array of larger diameter fuel rods for use in a nuclear reactor having liquid coolant flowing in an upward direction. Plenums are preferably provided in the upper portion of the upper smaller diameter fuel rods and in the lower portion of the lower larger diameter fuel rods. Lattice grid structures provide lateral support for the fuel rods and preferably the lowest grid about the upper rods is directly and rigidly affixed to the highest grid about the lower rods.