Abstract: Triangular lattice for LWR square fuel assemblies.

Abstract: A fuel assembly for a nuclear reactor, comprising a number of parallel fuel rods which are retained by means of spacer grids, arranged along the fuel rods, as well as guide thimbles wherein the guide thimbles, are fixed to the spacer grids. The guide thimbles with associated fuel rods are further fixed between a top nozzle and a bottom nozzle. In the top nozzle, through-holes are arranged for connection to a top sleeve joined to the upper end of the respective guide thimble. In the top sleeve, a first locking element is arranged for cooperation with a second locking element arranged on a guide sleeve, which guide sleeve is insertable through that hole in the top nozzle which corresponds to the respective top sleeve. The locking elements are interlocked in connected position by means of a locking sleeve insertable into the guide sleeve. The locking sleeve comprises a third locking element in the form of a through-opening arranged in the wall, a corbelled-out portion being arranged in the edge of the opening.

Abstract: A fuel rod for nuclear reactors which contains UO.sub.2 or a mixed-oxide (MOX) of UO.sub.2 and PuO.sub.2 as a nuclear fuel and a combustible reactivity control material e.g., Gd.sub.2 O.sub.3. A plurality of hollow UO.sub.2 or MOX pellets each having a hole along its central axis are spitted with a long bar of Gd.sub.2 O.sub.3 to form a pellet stack, which is inserted and sealed in a cladding tube to form the fuel rod of the present invention. Since the Gd.sub.2 O.sub.3 bar can be manufactured in a non-nuclear fuel manufacturing facility, it is not required to provide two separate lines, i.e., a line for handling Gd.sub.2 O.sub.3 and a line for handling UO.sub.2 or MOX fuel, in one manufacturing facility. The optimum design for the performance of the nuclear fuel is possible by changing the diameter and/or Gd.sub.2 O.sub.3 concentration of the Gd.sub.2 O.sub.3 bar depending on the desired performance of the nuclear fuel.

Abstract: A fuel bundle is disclosed in which interspersed part length fuel rods define between the end of the fuel rods and the upper tie plate void regions which are not otherwise occupied. Full length fuel rods adjacent to these regions are provided with an expanded upper plenum region which effectively increases the fuel rod diameter at the end of the upper two phase region of the fuel bundle. Under normal circumstances and a fuel bundle with only full length fuel rods, such an expansion of the upper regions of the fuel rods would cause unacceptable pressure drop. Where such expansion occurs adjacent the vacated volumes created by the part length fuel rods, unacceptable pressure drop does not occur. Consequently, and with the expanded plenum volume, a longer length of active fuel pellets can be accommodated within the full length fuel rods.

Abstract: A fuel assembly in the form of an elongated channel having several corners is connected to a coolant intended to flow through the channel. A bundle of similarly elongated fuel rods, retained by a plurality of spacers, is arranged in the channel, and arranged in the upper part of the fuel assembly, at least between a pair of spacers, is a sleeve formed of a sheet around the bundle. The sleeve has an external shape which conforms closely to the walls of the fuel assembly and is perforated by a large number of openings, the total surface of which is at least as large as the sheet surface remaining on one side of the sleeve.

Abstract: Two embodiments of a high uranium fuel plate are disclosed which contain a meat comprising structured uranium compound confined between a pair of diffusion bonded ductile metal cladding plates uniformly covering the meat, the meat having a uniform high fuel loading comprising a content of uranium compound greater than about 45 Vol. % at a porosity not greater than about 10 Vol. %. In a first embodiment, the meat is a plurality of parallel wires of uranium compound. In a second embodiment, the meat is a dispersion compact containing uranium compound. The fuel plates are fabricated by a hot isostatic pressing process.

Abstract: The zirconium cladding of a coolant-displacement rod of a nuclear reactor is precollapsed in the zirconium oxide stack of pellets which supports the cladding. Current is conducted through the cladding in an atmosphere at reduced pressure containing residual oxygen, to heat the cladding to a temperature at which its yield strength is reduced. Then, while the rod remains at this temperature, it is subjected to isostatic pressure which collapses the cladding uniformly. The formation, by reason of exposure to neutron flux, of a long unsupported gap in the cladding which might be collapsed under the pressure of the coolant is precluded. In addition, the rod retains its symmetry. The outer surface of the cladding is oxidized, facilitating the movement of the rod into its thimbles of the core and improving the resistances of the cladding to reaction with the coolant.

Abstract: The fuel element comprises a plurality of modular capsules (5) arranged in sequence axially within a sheath (2). Each of the capsules (5) comprises a tubular case (10) closed at both ends by a porous element (13, 14) and enclosing a stack of pellets (11) in contact with the inner surface of the case (10) without radial clearance. The outside diameter of the capsules (5) is such that a very small radial clearance exists between the outer surface of the capsule (5) and the inner surface of the sheath (2).

Abstract: A cluster of standardized reduced length burnable absorber rods include a plurality of middle rod sections having a multiplicity of different axial lengths and containing burnable absorber material in sealed chambers therein, a plurality of upper end spacer sections having a multiplicity of different axial lengths and each defining an empty space, and a plurality of lower end spacer sections having a multiplicity of different axial lengths and each defining an empty space. Each of the rods is formed of one middle rod section tandemly arranged between and interconnecting one upper end spacer section and one lower end spacer section. The three interconnected sections which form each rod being selected so as to provide the same standard combined axial length for each of the rods in the cluster thereof although the axial lengths of the middle rod sections can vary from rod to rod and thereby the axial location of the burnable absorber material along the rod can also vary from rod to rod.

Abstract: A coolant-displacement rod for a nuclear reactor including a stack of zirconium-oxide pellets in cladding of ZIRCALOY-4 alloy. The outer surfaces of certain of the pellets spaced at intervals along the stack are depressed. The cladding grows permanently when exposed to neutron flux but the zirconium oxide is dimensionally stable. Under the hoop stress impressed by the coolant on the cladding, the part of the cladding encircling each of the pellets with the depressed outer surface engages the outer surface compartmentalizing the pellets into sub-stacks. The formation of a long unsupported gap under the cladding which might collapse under the pressure and at the temperature coolant is prevented by forming a plurality of short unsupported gaps instead of one long gap.

Abstract: An automated fuel rod production system includes a radioactive powder fabrication and processing stage, a pellet fabrication stage, a pellet processing stage, a tube preparation stage and a fuel rod fabrication and inspection stage, all of which provide a continuous (paced) mode of operation from the conversion of a radioactive gas to powder, through the fabrication of the powder into pellets, to completion of the assembly of the fuel rods. Extra capacity is designed into the system at critical points in the powder processing and pellet fabrication and processing stages to facilitate the continuous, paced mode of operation.