Abstract: In a nuclear reactor, the core is composed of fuel assemblies disposed in side-by-side spaced relationships with an outer group thereof defining the periphery of the core and an inner group thereof positioned inwardly of the outer group. A baffle structure extends about the reactor core adjacent the fuel assemblies in the outer group. Any jetting of coolant fluid through the baffle structure will impinge upon fuel rods in the outer group of fuel assemblies so as to cause vibration of the fuel rods. To prevent such vibration, a plurality of annular anti-vibration grids are axially spaced along and connected to guide thimbles of the fuel assemblies in the outer group thereof between at least some of the support grids of such fuel assemblies. The annular grids are separate from and unconnected to the support grids.

Abstract: Spacer grids for a nuclear fuel assembly are arranged in superadjacent groups having grid springs and opposing dimples which contact a fuel rod passing through a cell of the spacer grid with a selected spring force. As fabricated, the lowermost grid exerts the greatest initial spring force on the rod; intermediate grids exert a smaller spring force; and the uppermost grid exerts yet a lower spring force. The fuel rod is supported laterally while it is permitted to age expand axially with little axial compression resulting from the spring forces of the springs and dimples, whereby bowing of the rod is diminished.

Abstract: A nuclear reactor fuel assembly for accommodating mutually parallel rods disposed side by side therein includes a spacer formed of two mutually parallel grid sections having sides, each of the grid sections including outer straps flatly facing the rods at which the grid sections are interconnected, each of the grid sections including main sleeves being positioned like positions of the same color in rows and columns disposed at right angles to each other on a chess board leaving a free intermediate position between each two occupied positions, the main sleeves dividing the grid sections into grid mesh openings at the positions each able to receive a respective rod therein, each main sleeve in one of the grid sections having edges and being aligned with a main sleeve in the other grid section forming pairs of main sleeves, connecting straps each interconnecting the main sleeves of a pair of main sleeves forming contact springs for rods, each of the connecting straps having a width being smaller than the circumf

Abstract: Disclosed is an interlocking egg-crate hexagonal grid for supporting a nuclear fuel pin in a hexagonal array. The grid is formed from strips bent at an angle of about 120.degree. at each vertex. Over some faces of each hexagonal cell the strips are coplanar but are arranged, by stacking and interlocking, to avoid any double thickness of metal in that plane. Springs and dimples are formed in the faces of each cell to hold the fuel pin substantially centered.

Abstract: A fuel assembly has a bundle of elongated fuel rods disposed in a side-by-side relationship so as to form an array of spaced fuel rods, an outer tubular flow channel surrounding the fuel rods so as to direct flow of coolant/moderator fluid along the fuel rods, a hollow water cross extending centrally through and interconnected with the outer flow channel so as to divide the channel into separate compartments and the bundle of fuel rods into a plurality of mini-bundles thereof being disposed in the respective compartments, and a plurality of spacers axially displaced along the fuel rods in each of the mini-bundles thereof. Each of the fuel rods includes an outer cladding tube with an inner clad surface and a plurality of fuel pellets contained within the tube. Each spacer is composed of a plurality of interleaved inner straps and an outer strap encompassing the inner straps.

Abstract: In a nuclear reactor fuel element for receiving mutually parallel rods, the improvement includes a rectangular grid-shaped spacer including planar webs crossing and facing the rods defining grid mesh openings receiving the rods, the webs including two outer webs forming an outer corner of the spacer and defining a corner grid mesh opening at the outer corner, the outer corner having an outward curve being curved in a direction parallel to the longitudinal direction of the rods, the outer webs having edges at the curve transverse to the rods being drawn inward toward the rods in the corner grid mesh opening forming a bevel in longitudinal direction of the rod.

Abstract: A spacer grid for a nuclear fuel assembly having grid springs and opposing dimples which contact a fuel rod passing through a cell of the spacer grid along arcuate surfaces to cradle the fuel rod and cushion any vibration impact between the fuel rods and the grid springs and dimples during reactor operation and during fuel assembly shipping. The increased bearing surface between the fuel rods and grids also serves to reduce fuel rod scratching during fuel rod insertion. The grid springs and dimples may also be provided with ramped edges to further reduce fuel rod scratching. Stiffening ribs may be on the grid springs and/or dimples. The cradling action of the grid springs and dimples reduces deviations in fuel rod position from a centered position in a spacer grid cell.

Abstract: A double lock joint structure is used in a reconstitutable fuel assembly for attaching the adapter plate of the assembly top nozzle in releasable locking engagement upon the upper end portions of the assembly guide thimbles. The joint structure includes axially extending slots defined in each guide thimble upper end portion permitting inward elastic collapse thereof to a compressed position and outward elastic return thereof to an expanded position. The joint structure also includes axially spaced upper and lower annular bulges formed in the upper end portion. The upper annular bulge has an outside diametric size greater than the inside diametric size of the adapter plate passageway when the guide thimble upper end portion is at its expanded position and less than the inside diametric size of the adapter plate passageway when the upper end portion is collapsed to its compressed position allowing insertion and withdrawal of the upper end portion into and from the adapter plate passageway.

Abstract: The invention relates to a spacer arranged to retain and fix elongated fuel rods into bundles insertable into a nuclear reactor fuel assembly, said spacer being of a zirconium alloy having a low neutron absorption. To counteract play and hence wear in case of increasing burnup when the springs relax and the rod diameter is reduced by shrinkage, the spacer is made with different textures in the springs (2, 3) and the surrounding structure (1, 6). The difference in texture gives the springs a great axial irradiation growth and the surrounding structure a small axial irradiation growth, which contributes to a remaining deflection tendency of the springs in relation to the surrounding structure during the life of the fuel assembly.

Abstract: An improved grid structure is provided for a nuclear reactor fuel assembly whose sole purpose is to promote a crossflow mixing of the coolant through the fuel assembly rather than the support of the fuel rods. The grid straps form an egg-crate configuration creating cell openings for receiving the fuel rods. Associated with each cell opening is at least one coolant flow mixing vane that projects over the cell opening and four dimple protrusions which are open to the flow of coolant therethrough. The dimple protrusions extend into the cell opening to a further extent than the mixing vane so as to prevent damaging impact of the fuel rod with a vane upon transverse movement of the fuel rod across the cell opening. In reducing the pressure drop of the coolant flow through the assembly, the height of the inner grid straps is substantially less than the height of the outer border strap.

Abstract: Vertical and axial movement of fuel rods relative to grid spacers in a fuel bundle of a BWR or PWR nuclear reactor is prevented by use of sleeves welded to various vertical positions upon a fuel rod, whereby the sleeves have horizontally and vertically oriented windows and slots for engaging protrusions and corner springs, respectively, located in the openings for receiving fuel rods of the grid spacers.

Abstract: A fuel assembly has a plurality of elongated fuel rods, a plurality of grid structures axially spaced from one another along the fuel rods between opposite ends thereof and supporting the fuel rods in a side-by-side spaced array, and a pair of tie plates disposed at the respective opposite ends of the fuel rods. Each of the fuel rods has a pair of end plugs sealing opposite ends thereof, with at least the end plug at one of the opposite ends of each fuel rod having an extension member thereon which extends axially outward from the end plug and is of a diameter less than that of the fuel rod. At least one of the tie plates has a plurality of holes defined by endless sidewalls formed therethrough between opposite sides of the tie plate and in an array which matches that of the fuel rods.

Abstract: Nuclear reactor fuel assembly having a grid-shaped spacer with square grid meshes, wherein mutually parallel rods are arranged, respectively, in a grid mesh, the spacer having flat outer straps extending transversely to the rods and an intermediate strip extending parallel to the rods between two of the respective outer straps, the intermediate strip being inclined relative to the two outer straps, including a rejection rise formed at the outside of the intermediate strip and extending in direction of a diagonal of a grid mesh located at a corner between the two outer straps, the rejection rise being disposed transversely to the two outer straps and being inclined downwardly towards two respective ends of the intermediate strip in longitudinal direction of the rods.

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: A nuclear reactor fuel assembly having a grid-shaped spacer for retaining fuel rods, the spacer includes four flat, sheet metal outer straps disposed on edge at right angles to the fuel rods defining corners of the spacer, inner sheet metal straps disposed within the outer sheet metal straps, the inner straps include two given inner straps each being transverse to one of two respective given outer straps at a corner of the spacer dividing the spacer into meshes for fuel rods including a corner mesh at a corner of the spacer and two other meshes laterally adjacent the corner mesh, a contact spring for a fuel rod disposed in the corner mesh, the contact spring having two end parts each being locked in a respective recess formed in one of the given inner straps locking the contact spring to one of the given outer straps, the recesses starting from an end edge of the one given inner strap parallel to the fuel rods, two extended arms in the corner mesh each being integral with a respective one of the end parts and

Abstract: An insert for providing a reduced inside diameter for a structural tube, specifically an instrumentation guide tube, of a nuclear fuel assembly. The insert has forming lobes which coact with the structural tube to plastically deform the structural tube and mechanically lock it with respect to grid straps of a grid assembly. The insert also has centering lobes to prevent it from being expanded in other than a coaxial alignment with the structural tube. An expansion tool is provided for sequentially registering with and expanding sequential forming lobes in a simplified manner whereby all of the operations necessary to assemble the structural tube in the fuel assembly can be easily and accurately performed.

Abstract: A nuclear reactor fuel of the kind comprising multi-pins (10) located in a hexagonal wrapper (11) and stabilized by a series of spacing grids (12) has an internal grid support cage (13) formed by six vertical limbs (20) inside the wrapper. The limbs of the cage have upturned parts (14) which engage into the cellular structure of the grids such as lying between two adjacent unit cells (16). The cells have tabs (21 in FIG. 3 and 52 in FIG. 5) which can be welded to the upturned parts.

Abstract: A fuel rod support grid includes interleaved straps arranged to form a matrix of hollow cells. Each cell receives one fuel rod and is defined by pairs of opposing elongated walls which are shared with adjacent cells. Each wall of the pairs thereof forming a single cell has one side which is a part of the perimeter of the single cell and has an opposite side which is part of the perimeter of one of several cells disposed about and adjacent to the single cell. The improvements incorporated by the support grid comprise a first set of dimples formed at an upper end of each wall of the pairs thereof defining each cell of the grid and a second set of dimples formed at a lower end of each grid cell wall.

Abstract: A grid structure of slotted straps interfitted at their slots to form cells containing fuel elements or thimbles. The straps are of nonuniform thickness having strips of substantially greater thickness than the regions between the strips. The strips of greater thickness extend parallel to the slots. The straps are joined along these strips of greater thickness. Grids of zirconium alloy resisting crushing are formed by joining intersecting straps by welds in the strips of greater thickness.

Abstract: A nuclear fuel assembly comprises two end pieces connected by guide tubes. Grids are distributed along the guide tubes and define passages distributed according to a regular pattern. Some of the passages receive the tubes. Other passages retain fuel elements parallel to the tubes. Individual sleeves containing a burnable poison are carried by the tubes, each in a space bounded by one grid on one side, by an other grid or an end piece on the other side. The length of the sleeves is selected for allowing differential thermal expansion of the tubes and grids. One end of each sleeve may be secured to lugs of an associated grid.

Abstract: A spacer grid for a nuclear reactor fuel assembly, comprising an assembly of two families of thin partitions which are respectively parallel in each family and perpendicular from one family to the next and which bound pockets of square section through each of which a fuel rod of the cluster extends, the walls of the pocket being formed with bearing points to retain the fuel rods of the cluster, wherein it comprises bearing bridges formed by profiled bosses produced in pairs on a sheet metal tongue obtained by making two longitudinal parallel slots in the thin partition on either side of such bosses, the bosses being oppositely directed in two adjacent pockets, and the reaction of the fuel rods on the bosses after they have been positioned in the grid produces a torque on the resilient sheet metal tongue, the deformation of the tongue thus enabling the assembly tolerances of the fuel rods to be absorbed in the grid. Application to nuclear reactor assemblies.

Abstract: An element for a core of a nuclear reactor, includes a square grid assembly formed of a plurality of spacers distributed over the length of the element, structural elements interconnecting the spacers, rods regularly disposed in the square grid assembly and surrounded by the spacers, including a plurality of the rods disposed at an edge of the core, and neutron-shielding material having a substantially square cross section respectively disposed in each of the plurality of rods at the edge of the core.

Abstract: A plurality of independent cells having a regular octagonal or circular cross section are arranged in the form of a lattice. Cross-sectionally square independent cells are substituted for two octagonal or circular cells in the central portion of the lattice arrangement. These two square independent cells are so formed that each side of the cells has the largest possible length when the cells are placed among the adjacent cells having a regular octagonal or circular cross section. Spacer support rods serving also as water rods are inserted into the square cells in such a fuel spacer, which consists of a combination of cells having a regular octagonal or circular cross section and cells having a square cross section as mentioned above, to form a fuel assembly.

Abstract: It has two groups of thin partitions, which are parallel in one group and perpendicular from one group to the next, which are grooved and nested to define square cavities. Support points are made in the walls of the cavity to hold in place the fuel elements. In each group, a thin partition is constituted by two superimposed sheets. The height of the first sheet is equal to double the height of the second sheet. A first sheet is positioned above the second sheet in one of the groups and below the latter in the other group. Each second sheet is nested into the first sheet of the other group.

Abstract: A nuclear fuel spacer grid with improved grid straps. The grid has an egg-crate array of interleaved grid straps creating cells for enclosing the fuel rods. Near beginning of life in the reactor, the grid straps bend in a spring-like manner to flexibly grip the fuel rods with their preferably rigid protrusions. In a cell, the protrusions on two non-opposing grid straps are closed to longitudinal coolant flow while the protrusions on the remaining grid straps associated with the cell are open to such flow. Near end of life the grid straps loose resiliency due to irradiation--induced stress relaxation and the fuel rod has a loose fit against the protrusions due to radiation effects. However, the fuel rod is held in position in the cell by the coolant flow therethrough which forces the fuel rod away from the closed protrusions and into contact with the open protrusions. The protrusions in one cell are coplanar. The protrusions in the cells lie in one of two longitudinally separated planes.

Abstract: A nuclear fuel spacer grid with improved outer straps. The grid has an egg-crate array of interleaved grid straps creating cells for enclosing the fuel rods. The grid also has four outer straps connected together in a square-shaped array surrounding the grid strap's heightwise edges. The outer straps have a central portion to which is attached the grid straps' heightwise edges. The outer straps also have a top and a bottom resilient lengthwise border portion extending vertically beyond and horizontally outwardly beyond their associated outer straps central portions.

Abstract: A spacer for supporting a plurality of fuel rods forming a nuclear fuel assembly. The spacer comprises a peripheral band surrounding a bundle of the fuel rods and a plurality of spacer framework units, each holding therein one fuel rod. The spacer framework units are welded or brazed to the peripheral band so as to be arranged inside the peripheral band. Spring members are integrally formed on each of the spacer framework units. The spacer framework units, the spring members and the peripheral band are made of a zirconium alloy containing 5-25% by weight niobium and 0.1-1% by weight chromium and/or iron.

Abstract: Spacer for centering fuel rods of fuel assemblies in water-cooled nuclear reactors, including a grid of sheet metal webs formed of a zirconium alloy and being disposed on edge, rigid bumps formed from at least some of the webs for contacting a fuel rod, at least some of the webs having relatively wide cutouts and relatively narrow lateral slots formed therein, and resilient contact elements formed of chrome nickel steel and having a head part, a base part, a resilient band connecting the head and base parts together into one piece and a bent-out point formed on the resilient band for contacting a fuel rod, the head and base parts of the contact element being insertable into the cutouts and movable into a locked position in the lateral slots formed in the webs.

Abstract: A nuclear reactor fuel assembly spacer grid having grid straps and a first type of spring clip. The grid straps define standard cells enclosing fuel rods and thimble cells enclosing control rod guide thimbles. The spring clip is bent to widthwise encircle a grid strap and has its two ends welded together. The first type of spring clip is used at a location on a grid strap having a standard cell and an adjacent thimble cell. The spring clip has a spring portion compressibly contacting the fuel rod in the standard cell. The spring clip also has a pair of separated flat portions straddling the control rod guide thimble in the thimble cell so as not to interfere with the guide thimble. The spring clip is made of a material having good radiation stress relaxation properties.

Abstract: In a fuel assembly for a nuclear reactor a fuel element spacer formed of an array of laterally positioned cojoined tubular ferrules each providing a passage for one of the fuel elements, the elements being laterally supported in the ferrules between laterally oriented spring members and oppositely positioned rigid stops, the wall thickness of the ferrules being relatively large and the height of the ferrules being relatively small to reduce hydride concentration in the ferrule material while maintaining relatively low flow resistance.

Abstract: A bracing grid (27) made from joggled strip (20) and which is one of a number of similar grids supporting fuel pins (26) in a fuel sub-assembly for a nuclear reactor is characterized in having the peripheries of the grids completed by unit edge cells (21). Where the periphery of the grids accommodate sub-assembly corner posts (30) the continuity of the unit edge cells is maintained around the corner posts.

Abstract: In a nuclear fuel assembly spacer providing passages for fuel rods or other elongated elements, a spring component of H-shape including a pair of spaced spring members of hairpin-like configuration connected by a retaining strap wherein an arched side of one of the spring members projects into one of the passages and the arched side of the other of the spring members projects into an adjacent one of the passages for resilient engagement with the fuel rods or other elongated elements extending through the passages.

Abstract: A grid for the support of nuclear fuel rods arranged in a triangular array. The grid is formed by concentric rings of strap joined by radially arranged web sections.

Abstract: A spacer for use in a fuel assembly of a nuclear reactor having thin, full-height divider members, slender spring members and laterally oriented rigid stops and wherein the total amount of spacer material, the amount of high neutron cross section material, the projected area of the spacer structure and changes in cross section area of the spacer structure are minimized whereby neutron absorption by the spacer and coolant flow resistance through the spacer are minimized.

Abstract: In a fuel assembly for a nuclear reactor a fuel element spacer formed of an array of laterally positioned cojoined tubular ferrules each providing a passage for one of the fuel elements, the elements being laterally supported in the ferrules between slender spring members and laterally oriented rigid stops.

Abstract: Apparatus and method for preventing the rotation of one or more elongated rods used in nuclear fuel assemblies include an end plug secured to one longitudinal end of such an elongated rod and having an out-of-cavity, non-round structure affixed thereto and configured to mate with a complementary shaped structure in a lower tie plate of a nuclear fuel assembly in such a manner as to prevent the rotation of the rod about its longitudinal axis. In one embodiment, the end plug includes a pair of flats formed on a portion of the end plug and configured to abut against a pair of flats formed on the outer surface of a cylindrical boss or sleeve of the lower tie plate, thereby to prevent the rotation of the rod. In another embodiment, four grooves, disposed 90.degree. apart about the periphery of an end plug of a rod form a spline. The grooves are configured to receive four, radially inwardly protruding, key members disposed 90.degree.

Abstract: Welding plates for laser beam welding of a fuel rod grid are provided, each welding plate having a surface with a set of equally spaced, parallel grooves and with a second set of such grooves perpendicular to the first set. Each of the welding plates is provided with openings therethrough at the points of intersection of the straps forming the grid, so as to expose those points of intersection to a laser beam for laser beam welding of the points of intersection. A vane side welding plate has the walls of the laser beam access openings placed so as to hold vanes extending from the straps in deflected position. Stand-off pins and clamping bolts are provided, the latter having heads with access openings for the laser beam. The welding plates are provided with protrusions which extend laterally thereof, the protrusions having precisely located holes with precision bushings therein.

Abstract: A nuclear reactor fuel assembly for a nuclear reactor comprises a housing with a wall and spacer means removably located within the housing, the spacer means comprising a plurality of spacer cells each adapted to receive an elongated fuel rod for the purpose of locating a bundle of such fuel rods in spaced-apart relationship within the housing. A portion of the housing which confronts the spacer means is provided at least at one location with a first locking means, and one of the spacer cells is provided with a second locking means movable between active and inactive positions. This second locking means is prevented from moving past the first locking means in the direction of elongation of the fuel rods when the second locking means is in its active position but is able to move past the first locking means when in its inactive position. The second locking means is moved from its inactive position to its active position by the insertion of a fuel rod into said one spacer cell.

Abstract: A nuclear reactor fuel assembly spacer grid. The grid straps form an egg crate configuration creating standard cells to enclose the fuel rods. The standard cells have at least one of their straps with an integral spring portion extending into the standard cell and pushing against the fuel rod. A distinct backup spring is positioned transverse to and behind each of the spring portions of the straps and is positioned so as not to touch the fuel rods. The straps are made of a material having a low neutron capture cross-section while the backup spring is made of a material having good radiation stress relaxation properties.

Abstract: A storage device for receiving spent nuclear fuel elements comprising a plurality of chambers which are separated by partitions from each other. The partitions form arches in such a way that relatively large arches alternate with relatively small arches. Each arch of relatively large size engages physically an arch of relatively small size, and vice versa. Considering two contiguous identical partitions, this implies that the partitions are arranged out of registry.

Abstract: The grid for the parallel rows of tubes is composed of metal guide strips and spacer strips. The guide strips are disposed in pairs with semi-cylindrical portions defining circular openings for the tubes. The spacer strips are formed with bent portions to bear against the semi-cylindrical portions of the guide strips as well as rectilinear portions which are radial to the tubes.

Abstract: A composite nozzle for a fuel assembly adapted for installation on the upper or lower end thereof and which is constructed from two components. The first component includes a casting weldment or forging designed to carry handling loads, support fuel assembly weight and flow loads, and interface with structural members of both the fuel assembly and reactor internal structures. The second component of the nozzle consists of a thin stamped bore machine flow plate adapted for attachment to the casting body. The plate is designed to prevent fuel rods from being ejected from the core and provide orifices for coolant flow to a predetermined value and pressure drop which is consistent with the flow at other locations in the core.

Abstract: A nuclear fuel assembly grid (12) having four substantially solid perimeter plates (28) forming a rigid quadrangle (20) surrounding the fuel elements (36) and having stop surfaces (32) formed on the internal surfaces thereof for contacting each adjacent fuel element. A plurality of interlaced strips (24) are attached to and extend from each plate to the oppositely facing plate, forming a lattice of regularly spaced openings (16) through which the fuel elements traverse the grid. These strips are of two types, the first consisting of two perpendicular center strips (44,44') that divide the grid into four symmetric quadrants, each center strip having a spring tab (48') projecting into each opening (16') contiguous to the center strip. The second type of interlaced strip consists of the remainder of the strips (52), half of which are oriented parallel to one center strip and the other half are oriented parallel to other center strip.

Abstract: The present invention relates to a spacer grating for fuel element in a nuclear reactor of the PWR type, said grating being constituted by intersecting plates. Over the greater part of the walls equipped with springs, double springs comprise two active parts on either side of the wall on which the double spring is placed, allowing the symmetrical action of this spring on two different pencils inside two adjacent cells. On the other walls equipped with springs, single springs comprise one active part only, disposed in one of the two cells separated by the wall on which is placed the spring of which the other part is not capable of coming into contact with a fuel pencil. The invention is particularly applicable to the manufacture of fuel assemblies in nuclear reactors of the PWR type.

Abstract: A spacer grid assembly provides elastic support and secure positioning of fuel elements in a nuclear reactor. This spacer grid assembly comprises two families of thin perforated sheets, the sheets of one family being parallel to each other and perpendicular to the sheets of the other family. The interlaced assembly of these interfitting sheets forms a three-dimensional lattice of square-sectioned cells for positioning and securing the fuel elements vertically. This spacer grid assembly comprises large recesses within the cell walls that define the spring means. The spring means comprises two plates shaped as a flexible vault, a sheet stud connecting these plates, and two triangular strips integral with this sheet stud on one side and opposite each other on this same side, and ending in circular and protruding pads. These pads contact the fuel element and transmit the bearing power of the spring means to the fuel element.

Abstract: A grid for a nuclear reactor fuel assembly which includes two sets of interwoven straps which form square openings of egg-crate configuration. One set is placed on top the other with the openings in alignment to receive fuel rods. The vertically aligned square openings thus constitute single cells through which fuel rods are adapted to extend. The top edges of straps in the bottom grid are provided with narrow slots which extend in multiple rows diagonally across the grid when the straps are assembled. A spring, one for each row of diagonal slots, is threaded through the slots before the top grid is set in place. Each single cell contains two pairs of vertically spaced dimples on adjacent walls of the straps as in conventional construction. That portion of the spring, which extends through each cell, engages a side of the fuel rod in the cell and urges it into contact with the dimples, thus providing five points of support for each fuel rod which extends through the cells.

Abstract: A spacer grid for a nuclear fuel assembly wherein hangup between diagonally adjacent fuel assemblies in the reactor core during loading and unloading is essentially precluded by providing an inclined plane deflection surface at each corner of the spacer grid.

Abstract: The present invention relates to a device for fixing a spring to a spacing grid for fuel elements of nuclear reactors.This device is characterized in that it is constituted by two retaining bridges (8) for the spring (6) made in one of the thin metal sheets constituting the grid and maintaining the spring (6) against said sheet. Two other bridges (10) located outside the bridges (8) constitute abutments for stopping the translation of the spring (6). A double stamping (12) made in the thin metal sheet at the approaches of each retaining bridge (8) constitute a precise translation guide for the spring (6).Application to the spacing grids of fuel elements of nuclear reactors.

Abstract: Advantage is taken of the non-uniform axial neutron flux density distribution in a nuclear reactor core by using fuel rod spacers of low neutron absorption in high neutron flux density regions and fuel rod spacers of low coolant flow resistance in the lower neutron flux density regions of the core, this spacer combination also providing higher fuel bundle thermal limits.

Abstract: A spacer grid for fuel assemblies in a water reactor is provided. The grid shell is shaped so that a pressing in Zircaloy can be made. Cross members in a lattice in the shell provide spacing for the fuel pins of the fuel assembly. Each fuel pin has its own cell in the lattice, and at least some of the joints between the members comprise two attachment points spaced along one of the members at a single intersection.