Abstract: The spacer grids consist of interlaced metal straps defining a regular lattice of cells. A spring for holding a fuel rod against bearing stops is fixed on at least one wall of each of the cells. In its part which constitutes the wall of the cell, the strap includes at least one stop produced by cutting and pushing the metal of the strap into the cell, so as to limit the displacement of a fuel rod housed in the cell. Stops for limiting the displacement of the fuel rod are placed preferably o the walls of the peripheral cells or corner cells of the spacer grid, opposite a peripheral belt of the spacer grid. The invention also relates to a fuel assembly which includes, in addition to structural spacer grids, end grids and additional mixing grids interposed between the structural spacer grids.

Abstract: A nested sleeve grid restraint system and a method for making a nested sleeve grid restraint system are disclosed. The nested sleeve grid restraint system comprises an insert tube installed in and secured to the intermediate spacer grid and concentrically around a fuel assembly instrumentation tube, the insert tube having ends extending from the intermediate spacer grid, respectively, above and below the intermediate spacer grid; two spacer sleeves, each having flared ends; the spacer sleeves each being fitted concentrically around the fuel assembly instrumentation tube, respectively, above and below the intermediate spacer grid; the flared ends of the spacer sleeves fitting over the ends of the insert tube extending above and below the intermediate space grid whereby the insert tube nests in the spacer sleeves.

Abstract: The ferrule spacer includes a ferrule having an elongated slot with a pair of tabs projecting laterally into the slot. An elongated spring has opposite ends bearing against the interior wall of the ferrule and flats overlying the tabs along the outside of the ferrule. The mid-span portion of the spring projects in a central aperture between the ferrule tabs for biased bearing engagement against the fuel rod. The fuel rod is maintained against oppositely disposed stops formed on the ferrule. The spring is inserted and removed from the inside of the ferrule.

Abstract: A spacer grid spring (6) consists of a single metal leaf including two end parts (6a, 6b) substantially in the same plane and a central part (6c) out of the plane of the end parts (6a, 6b). At least one of the end parts (6a, 6b) is laterally provided with two flanges (6d, 6e) folded out of the plane of the end part (6a, 6b), in the opposite direction from the central part (6c) of the spring (6). The call wall (5) intended to receive the spring (6) includes, in an arrangement adjacent to each of two dimples (7a, 7b) placed at the ends of the wall (5), a part (8a,8b) for holding an end (6a, 6b) of the spring, and an opening (10a, 10b) passing through the wall (5) adjacent to the holding part (8a, 8b).

Abstract: A spacer for a nuclear fuel bundle comprises a plurality of discrete, generally cylindrical ferrules, with each ferrule having a pair of circumferentially spaced fuel rod contacting portions along one side of the ferrule and three superposed openings in the ferrule along an opposite side thereof. A leaf spring having opposite end projecting portions and a central projecting portion is disposed between adjacent ferrules with the end projecting portions and the central portion disposed within the openings of the ferrule. The central portion includes a boss projecting inwardly for engagement against the fuel rod in one ferrule and the end projections contain bosses projecting inwardly and spaced from the fuel rod of the one ferrule. The end projections bear against an adjacent ferrule. The spring is captured between the two ferrules and contacts the ferrules at a plurality of laterally and vertically spaced contact points so that the spring is stabilized against flow-induced vibration.

Abstract: With an arrangement that the axial distance from the upper end of a first opening area to the upper end of the second opening area is equal to the axial distance from the upper end of a first coupling member to the upper end of a second coupling member, when a spring member is moved upwardly relative to round cells, the upper end of the second coupling member comes into contact with the upper end of the second opening area, and the spring members receives upwardly acting forces from fuel elements. The spring member is thereby prevented from inclining with respect to flow of a coolant. Simultaneously, the upper end of the first coupling member contacts the upper end of the first opening area, and the spring member is stably held in a condition where it is aligned with the direction of the coolant flow.

Abstract: A method of forming a nuclear fuel assembly grid, as well as the resulting grid itself, are disclosed. In the formation of the grid, formed straps having slits are prepared, arranged into a grid form by intersecting the straps with each other through the slits, and the intersections of the associated straps are brazed. Prior to the step of arranging the straps, those portions to be brazed are subjected to a pretreatment, in which an paste, prepared of a mixture of a filler metal and a vehicle, is applied to the portions to be brazed to form a thin film thereon.

Abstract: A spacer includes a plurality of ferrules welded to one another to form a structural integral matrix for locating fuel rods in a fuel bundle. Each ferrule has a pair of stops along one side of the ferrule and a central opening along its opposite side. An elongated flat spring having openings straddling a central cross-piece is disposed along an outer edge of the ferrule with the spring openings receiving band portions of the ferrule above and below the opening through the ferrule. The intermediate cross-piece bears against an adjoining ferrule whereby the end portions of the spring bear against the rod in the one ferrule, biasing it against the opposite stops. Thus ferrule/spring construction reduces the quantity of material of the ferrule, thereby improving performance without sacrificing structural integrity.

Abstract: A grid-shaped spacer includes a sheet-metal web having a web aperture formed therein defining two spaced mutually opposite aperture edges. The aperture edges oppose an elongation of an elongate spring which is curved about a direction transverse to its own longitudinal direction and which has a tab that engages through the web aperture at each of two spring ends. At least one of the tabs is snapped into a notch formed in one of the spring edges opposing the elongation of the spring.

Abstract: A fuel assembly and a spacer for a boiling reactor comprises an elongated fuel channel which is connected to a coolant intended to flow therethrough. In the fuel channel there is arranged a bundle of also elongated fuel rods retained by a plurality of spacers. The spacers have an external spacer frame which is provided all around with a plurality of openings. There is arranged, at the inside of the spacer frame, an edge which is obliquely positioned in relation to the longitudinal direction of the fuel assembly and which extends in an inclined manner in a direction downstream of the spacer and toward the corner of the spacer to deflect coolant to the fuel rods arranged at these corners.

Abstract: A fuel assembly is presented in which a plurality of support grids are disposed along the longitudinal direction of the fuel rods. The straps forming the grid cells of the support grids are provided with mixing vanes for generating turbulent flow of the cooling water passing through the grid cells. In a plan view of the support girds, each of the mixing vanes protrudes inwardly of the grid cells and is disposed along a positive diagonal direction and a negative diagonal direction. This configuration of the mixing vanes are effective in preventing the generation of systematic vibrations in the fuel assembly by canceling the effects of the turbulent flows of the cooling water. The direction of protrusion of the mixing vanes can be in two diagonal directions within one support grid, or it can be unidirectional along either diagonal direction within one support grid.

Abstract: A fuel assembly comprises a plurality of fuel rods, tie plates for holding both ends of these fuel rods, and spacers which support these fuel rods. The spacer comprises a plurality of cells into which the fuel rods are inserted respectively, the adjacent cells being joined to each other at axial ends thereof, whereby a space between these cells being held or retained, and a plurality of loop springs held respectively on the cells. Each of the loop springs has a pair of resilient members which are located within the pair of adjacent cells and which urge the fuel rods in a radial direction, and a pair of connections which connect axial ends of the resilient members to each other. Each of the connections have a passage through which coolant flows axially and which is defined by a closed peripheral wall. The closed peripheral wall is not uniform in thickness. The pair of adjacent cells have at axial end portions of peripheral walls openings for accommodating or receiving the connections of the loop spring.

Abstract: A boiling water reactor fuel assembly having a lowered fuel rod support plate and increased fuel rod length while restraining the fuel rods against lateral vibration.

Abstract: Spring assemblies are employed in adjoining ferrules of a spacer in a nuclear fuel bundle to bias the fuel rods against stops and hence position the fuel rods in the spacer. The spring assemblies in one form include back-to-back spring bodies having central leaves with forward projections extending through rectilinear openings in adjacent ferrules to engage fuel rods to bias the rods against stops at the opposite sides of the ferrules. Outer pairs of leaves straddle the central leaf and project rearwardly and join the spring bodies one with the other whereby the central leaves, end portions of the springs connected to the central and outer leaves, and the outer leaves act as paired springs in series, providing a low spring constant. In another form, a single spring body has a central leaf with a projection extending through an aperture of a ferrule to bias the fuel rod. The outer leaves bear against the outer surface of the adjoining ferrule.

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 nuclear fuel rod spacer grid is formed of slottedly interlocked sets of flat strips. One set of strips is formed with integral coplanar tab portions which have one or more edge portions bent at angles to form integral mixing vanes.

Abstract: A spacer array is disclosed in which alternating cells are disposed at differing elevations. In a preferred octagonal spacer cell array, alternate fuel rods within the rows and columns of the fuel bundle matrix are surrounded by octagonal spacer cells at a first elevation. Likewise, and in the same preferred octagonal spacer array, the remaining alternate fuel rods within the rows and columns of the fuel bundle matrix are surrounded by octagonal spacer cells at a second elevation. The octagonal spacer cells of the spacer array at one level adjoin the octagonal spacer cells of the spacer array at an adjacent level. Specifically, each octagonal spacer cell has the top and/or the bottom of as many as four of its eight sides disposed for joinding with one side of as many as four octagonal cells in an adjacent cell layer. Each cell has approximately 0.6 of an inch height, or one-half the 1.2 inch height of the prior art.

Abstract: An all Zircaloy spacer having integral springs and single metallic layer spacer thickness between fuel rods is disclosed. Each spacer cell includes upper and lower octagonal crowns. These octagonal crowns have a full panel height adjoining the defined sub-channel volume between fuel rods and half panel heights adjoining adjacent cells. The crowns at opposite ends of each octagonal spacer cell are designed to interleave to form a single wall thickness of the spacer material. Accordingly, half wall heights at one crown are defined toward the spacer cell while half wall heights at the other crown end are defined away from the spacer cell. By inverting and adjoining the respective spacer cells at their respective crowns, the crowns form upper and lower crown matrices holding adjoining cells of the spacer together. From two adjacent sides of the four sub-channel adjacent full height sides, cell legs extend between the crowns with upper and lower stops immediately adjacent the crowns.

Abstract: A boiling water reactor includes fuel assemblies having a case containing fuel rods which are parallel to walls of the case. Flow subchannels are formed by each four of the fuel rods. At least two and preferably four vanes in the flow subchannels are tapered in a vertical coolant flow direction and are three-dimensionally curved in such a way as to generate a swirl in the coolant flow. It is therefore possible to obtain a relatively high output from the fuel assembly.

Abstract: An improved ferrule spacer for use with high density fuel rod arrays within boiling water reactor fuel bundles is disclosed. Ferrules are constructed in mating ferrule pairs. Each ferrule is divided into upper and lower ferrule halves. One ferrule half has sides thereof with the walls removed. The other ferrule half has its in place. The ferrule pairs are confronted with one ferrule inverted with respect to the other and with each complete ferrule wall of one ferrule half being juxtaposed to a ferrule half at a missing wall. Preferably, and at the point of tangency between the ferrule pairs, an aperture for receiving and confining an "H" type double loop spring is defined. The disclosure includes ferrules having a circular surround for the fuel rods and ferrules having an octagon sectioned surround for the fuel rods. Each member of the ferrule pair is symmetrical and completely interchangeable to provide for both convenient assembly and a small inventory of assembly parts.

Abstract: A gridlike spacer for fuel assemblies having rods in a bundle, includes polygonal grid meshes having ribs intersecting at corners and extending transversely to the rod bundle between the rods of the rod bundle. The ribs have lateral surfaces facing the rods penetrating the meshes. Springs each protrude diagonally into at least one corner of a respective one of at least a majority of the grid meshes. Each of the springs has a middle part for laterally supporting a given rod penetrating the respective mesh. The middle part is a cylinder segment curved convexly about an axis of curvature at right angles to the rod bundle. Each of the springs has two spring ends adjoining one another in the direction of the rod bundle. The middle part changes over at the spring ends with a convex curvature into two legs being approximately parallel to the rod bundle. The legs are supported at least on the lateral surface of one of the ribs facing toward the given rod.

Abstract: A plurality of fuel rods containing fissile material are arranged in triangle lattices. A plurality of water rods groups are arranged among the fuel rods. Each of the water rods groups includes no fuel rod but a plurality of water rods which are arranged adjacently each other in triangle lattices having substantially same pitch as the fuel rods. The water rods groups are arranged not adjacently each other, and are surrounded with the fuel rods. the outer diameter of the water rod is smaller than the pitch. The fuel assembly is able to suppress increment of pressure loss because of formation of coolant path among adjacent water rods. Further, void reactivity coefficient is able to be small.

Abstract: Method of making a fuel assembly lattice member and the lattice member made by such method. The method includes placing a plurality of elongate metal straps on a computer controlled conveyor which successively conveys the straps into alignment with each of a plurality of computer controlled piercing and drawing dies belonging to a progressive die machine. The dies are selectively actuated by the computer to form such elements as curved deflector vanes and spring members on each strap member. After the piercing and drawing operations are completed, the straps are joined by welding to form a lattice member of hexagonal cross section, the lattice member defining a plurality of rhombic-shaped fuel rod cells and a plurality of generally rhombic-shaped guide tube thimble cells therethrough. The rod cells are capable of receiving respective ones of a plurality of fuel rods and the thimble cells are capable of receiving respective ones of a plurality of thimble tubes.

Abstract: A nuclear fuel assembly for a BWR comprises a plurality of fuel rods, a polygonal channel box surrounding the fuel rods, a plurality of spacers axially spaced from each other and each keeping the fuel rods laterally spaced from each other, and a plurality of vanes disposed only in a region at and around a corner within the channel box, for generating swirling flows in the region to thicken a liquid film on each fuel rod in the region.

Abstract: A nuclear fuel assembly grid (1) has a plurality of flat strips (10,12) that are orthogonally interlaced along vertical slots (38,60) through their upper or lower edges and welded together to form an egg crate-like array of four-walled cells (14) for receiving respective fuel rods (16), each cell including springs (20,30) and arches (32,34) projecting from the walls for contacting and supporting a respective fuel rod in the interior of the cell. At least some of the cells having flow deflection vanes (36,56) projecting integrally from a cell wall into the interior of the cell without contacting the fuel rod. Preferably, the vane is bent along a bend line (52) that is parallel to the upper edge (24) of the strip, into the interior of the cell, thereby forming an angle of between about 15 degrees and 30 degrees relative to the plane defined by the body, or plate portion of the strip.

Abstract: The grid comprises two sets of straps intersecting and fixed at their points of intersection, delimiting cells designed to be crossed some by thimble guides and the others by fuel rods, fitted with mixing vanes. It is provided with a surround carrying guide vanes, connected to at least some of the thimble guides. It is suitable for use in fuel assemblies for pressurized water reactors.

Abstract: A spacer sleeve for positioning and restraining a nuclear fuel rod in a nuclear fuel assembly, having a thin walled tubular member having an inner wall and an outer end, and extending a height from a lower end to an upper end and being positioned around the fuel rod to form an unrestricted coolant flow passage along the height of the tubular member, the flow passage having a cross-sectional flow area formed between the fuel rod cladding and the inner wall of the tubular member, and a thin tab extending from the tubular member into the unrestricted flow area and secured to a portion of the cladding of the fuel rod.

Abstract: A spacer for a fuel assembly of a pressurized water reactor includes a first group of first webs standing on end and extending parallel to one another in a plane. Each of the first webs has longer sides and shorter sides. One of the longer sides of each of the first webs has a slit formed therein with a narrowed point and an impressed indentation. A second group of second webs stand on end and extend at right angles to the first webs. Each of the second webs has longer sides and shorter sides. Another of the longer sides of each of the second webs has a slit formed therein with a narrowed point and an impressed indentation. Each respective one of the first webs is connected to a respective one of the second webs to form a grid by inserting the webs into each other at the slits and locking the narrowed point of one web into place in the impressed indentation of another web with a plug-in connection.

Abstract: A spring design particularly suitable for use in the core of a nuclear reactor includes one surface having a first material oriented in a longitudinal direction, and another surface having a second material oriented in a transverse direction. The respective surfaces exhibit different amounts of irraditation induced strain.

Abstract: An improved spacer is disclosed which contains an Inconel grid and a Zircaloy surrounding band. The Inconel grid can be fabricated from the extremely thin and highly elastic spring metal utilizing a modification of a prior art cell construction that includes paired inwardly bent vertical spring legs with cantilevered and rod encircling upper and lower arm pairs The spring legs extend at spaced apart locations between the upper and lower arm pairs and have a medial spring rod contacting portion for biasing the rods into stops on the rod encircling arm pairs. The springs at the upper and lower ends are provided with spring dimple stops to prevent over stressing of the spring during assembly or handling of the fuel bundle into which the spacer is incorporated. The rod encircling arm pairs have an offset from center where the two arms meet at their distal ends to complete encirclement of the rods. This offset from center enables the cells to be fastened in cell pairs at their respective embracing arms.

Abstract: Grid strips for a nuclear fuel assembly grid have elongated weld tabs. The weld tabs are bent against the strips along the intersection with an adjacent orthogonal strip. The tabs are dimensioned and positioned to initially extend substantially the entire length of the intersection of two grid strips. The tabs are then melted during the welding process.

Abstract: In a fuel bundle having a matrix of parallel side-by-side fuel rods supported between a lower tie plate and an upper tie plate, a new ferrule and spring construction for the required spacers used to maintain the fuel rods in their required precise side-by-side alignment is disclosed. Paired ferrules are each provided with apertures for capturing a single spring between the ferrules. The springs are provided with a continuously looping main body having protruding tabs on opposite sides of the springs. The paired ferrules are confronted at their respective apertures for the capture of the springs. The shape of the apertures permits insertion of the spring after the ferrules have been welded together. The springs are compressed while being inserted. After insertion the springs return to their original shape and are confined between the ferrules. After insertion of the fuel rods, the springs are compressed to an intermediate position, but are still confined within the ferrule apertures.

Abstract: A fuel bundle having spacers optimally deployed is disclosed wherein the distance between the spacers varies along the length of the fuel bundle. The fuel bundle has a dense fuel rod array (preferably in the range of 10.times.10). It includes at least one part length rod extending from the lower tie plate toward but not to the upper tie plate, which part length rod terminates at a spacer and defines under the upper tie plate overlying the end of the spacer a vent volume for the preferential venting of vapor moderator (steam) from the fuel bundle. A vertical spatial distribution of the spacers is disclosed in which the bottom spacers in the single phase region of the fuel bundle are relatively closely vertically spaced and the upper spacers are relatively more distantly vertically spaced one from another.

Abstract: A fuel assembly for a nuclear reactor with a number of parallel fuel rods which are retained by means of spacer lattices and guide tubes (3), which guide tubes (3) are also fixed to the spacer lattices, a top tie plate (4) and a bottom tie plate between which the guide tubes (3) with associated fuel rods are fixed. The top tie plate (4) has been provided with through-holes (10) for connection to a top sleeve (7) joined to the upper end surface of the respective guide tube (3). According to the invention, there is arranged inside the top sleeve (7) a first locking element (9) for cooperation with a second locking element (13). This is arranged on a guide sleeve (11) which is insertable through a hole (10) in the top tie plate (4), which hole corresponds to the respective top sleeve (7).

Abstract: There is disclosed a grid in a nuclear fuel assembly for supporting fuel rods and thimbles, which includes a plurality of elongated straps intersecting perpendicularly with each other to define a plurality of grid cells. A plurality of engaging units are provided on the grid cells for supporting thimbles, respectively. Each engaging unit includes at least one engaging member provided on at least one of the opposite ends of the straps of the grid cell and defining an engaging portion. A plurality of cylindrical sleeves are arranged in the grid cells for supporting thimbles, respectively. Each sleeve has at least one engaging projection associated with the engaging portion of the engaging member. The engaging projection of the sleeve and the engaging portion of the engaging member are formed such that when the sleeve is turned circumferentially, the engaging projection is held in engagement with the engaging portion.

Abstract: A spacer for a fuel bundle is disclosed in which a grid type construction provides an approximation to a traditional ferrule spacer. First and second sets of diagonally extending strips of Zircaloy are utilized extending along opposite diagonals across a square sectioned spacer. One set of strips is disposed in a first parallel array along a first diagonal, with each strip of the set being spaced from other strips of the set at rod width spaced intervals along the second and remaining diagonal. The other set of strips is disposed in a second parallel array along an second diagonal, with each strip of the set being spaced from the other strips of the set at rod width spaced intervals along the first diagonal.

Abstract: A spacer grid for a nuclear fuel assembly comprises a plurality of sets of plates which are interleaved and mutually interconnected to define cells each for receiving a fuel rod and further comprising a plurality of hairpin springs each carried by and retained on a respective one of the plates and each projecting into at least one respective cell when in released condition. Each spring is provided with one or two retention spurs arranged for retaining it temporarily in a retracted condition with respect to the respective plate. The retention spurs are releasable by a force of predetermined direction applied on the spring.

Abstract: A bracing grid suitable for use in a light water reactor has a plurality of mutually intersecting sets of plates defining cells which receive fuel rods. The plates carry springs for retaining the rods by friction. Each spring is formed has a U legs located each on one side of a plate, the branch being for contact on the elements in two mutually adjacent cells separated by the plate. The two legs are connected by a loop straddling the plate and are connected to each other by a weld at the base of the loop, through a window formed through the plate. The legs of each spring are also mutually connected by mechanical locking means which retain the two legs with respect to each other and with respect to the respective plate.

Abstract: An improved spacer is disclosed which contains an Inconel grid and a Zircaloy surrounding band. The Inconel grid can be fabricated from the extremely thin and highly elastic spring metal utilizing a modification of a prior art cell construction that includes paired inwardly bent vertical spring legs with cantilevered and rod encircling upper and lower arm pairs. The spring legs extend at spaced apart locations between the upper and lower arm pairs and have a medial spring rod contacting portion for biasing the rods into stops on the rod encircling arm pairs. The springs at the upper and lower ends are provided with spring dimple stops to prevent over stressing of the spring during assembly or handling of the fuel bundle into which the spacer is incorporated. The rod encircling arm pairs have an offset from center where the two arms meet at their distal ends to complete encirclement of the rods. This offset from center enables the cells to be fastened in cell pairs at their respective embracing arms.

Abstract: A spring-and-spacer assembly for maintaining fuel rods upright in a fuel assembly of a nuclear reactor core is provided. The spring is in the form of a continuous loop with first and second legs having mid-leg rod-contact regions. Bend regions are positioned on each side of each contact region extending toward the interior of the loop spring. In most positions, the spring is used to load two adjacent fuel rods. In configurations in which there is an unpaired fuel rod, a plate having a tab for contacting the spring is provided. The spring provides the desired force, such as about 2.5 pounds per fuel rod, in a small rod-to-rod spacing of less than about 0.14 inches.

Abstract: A spacer with a spring construction for the fuel bundle having matrix of parallel side by side fuel rods supported within a fuel channel between a supporting lower tie plate and holding upper tie plate is illustrated. The spacers each have a corresponding matrix of individual ferrules each surrounding the discrete fuel rods to be spaced within the matrix of fuel rods at any given elevation within the fuel bundle. Each of the individual ferrules surrounding the individual fuel rods are provided with stops against which the fuel rods are biased to ensure the required side-by-side spacing. Each ferrules must have at least one spring for forcing the fuel rods against the stops of its spacer ferrules to enable the spacer to assure required side-by-side alignment of the fuel rod. The springs are provided with a continuously looping main body having protruding tabs on opposite sides of the springs.

Abstract: A spring-and-spacer assembly for maintaining fuel rods in a upright preferred position in a fuel assembly of a nuclear reactor core is provided. The spring has a leg portion and two loop portions, one at each end of the leg. Each loop engages an ear formed in a ferrule of the spacer. Each loop contains a dimple which contacts an ear of the ferrule. The central leg portion has a dimple, or a projection, which contacts a fuel rod and biases the fuel rod against stops. The spring load is transmitted to the ferrule ears by the dimples in the spring loops. Preferably, the spring rotates about the dimple when flexed, contributing to spring flexibility. The high spring flexibility permits use of the spring in connection with small rod-to-rod spacing fuel assemblies. This construction permits providing a low-mass, low-surface area spring, in turn providing for low neutron absorption and low flow obstruction.

Abstract: A nuclear reactor fuel assembly includes at least one uprightly disposed spacer having a grid of intersecting sheet-metal struts defining meshes therebetween. Mutually parallel rods are each disposed in a respective one of the meshes. Strip-like contact springs are parallel to the rods and each have a side facing toward and a side facing away from a respective one of the struts. Each of the contact springs are disposed in a respective one of the meshes and have two strip ends both being retained on the one strut. Each of the contact springs have a contact location being resilient relative to the one strut for contacting a rod. The contact location is spaced apart from both of the strip ends. Each of the contact springs has an undulatory transverse curve disposed at the contact location on the side of the contact spring facing toward the one strut. The contact springs are continuously smooth and flat from the contact location to the strip ends resting on the one strut.

Abstract: A spring member is formed of at least two layers metallurgically bonded together uniformly and having significantly different rates of irradiation growth, so that the differential growth of the layers results in increased stress in a predetermined direction. The layers may be of different metals or of similar metals which have been treated to give them different growth rates, such as zircaloy with different tin and oxygen content. Examples of other properties which may be used to obtain differential growth rates for the two layers when they are of material with substantially the same constituents are alpha-beta phase transformation temperature, the annealing temperature, the work history, partial recrystallization, and precipitation hardening.

Abstract: An improved nuclear fuel assembly (10) of the type having a plurality of intersecting metal strips (14) welded at the strip intersections (32). At least some of the strips (16a, 18a) have nonlinear upper or lower edges (32a, 44a) at the intersections such that some of the intersection welds (34) at the strip upper or lower edges are at different elevations (34b) relative to intersection welds at other upper or lower edges (34a, 34c, 34d).

Abstract: A nuclear fuel rod support grid has a plurality of straps being interleaved with one another to form a matrix of hollow cells. Each cell receives one fuel rod and is defined by intersecting pairs of opposing wall portions of the straps which are shared with adjacent cells. A plurality of fuel rod engaging and clamping springs and dimples are associated with the wall portions of the straps and protrude into the cells so as to clamp a fuel rod therebetween. A pair of spacers separate from the grid straps but detachably mounted to the wall portions thereof defining each cell are installed in each cell along the strap walls portions defining each cell and at a pair of diagonal opposite corners of the cell. Each spacer has a right angle configuration in cross section for fitting into the respective one cell corner. One spacer supports the springs and the other spacer supports the dimples.

Abstract: A hairpin spring for holding a fuel rod in a fuel assembly grid consists of a metal strip bent to form two mutually confronting legs arranged to be welded together locally. At least in a zone which bears on the other leg, one of the legs is U-shaped and straddles the other leg through a respective window of the grid. The legs of the U may be formed as appendices bent substantially at 90.degree.. The arms may also close up slightly so that the other leg can snap thereinto or flare for self-centering of the other arm.

Abstract: A bimetallic spacer for supporting fuel rods in position in a nuclear reactor fuel assembly substantially comprises inner and outer structural elements of a first metallic material and spring elements of a second metallic material. The structural and spring elements together define a lattice, the interstices of which receive the individual fuel rods. The structural elements and spring elements in the spacer are connected together by forming the structural elements with openings and fitting the ends of the spring elements in the openings. At one end of the opening in the structural element, two slots can be provided for forming a tongue-shaped member which is moved aside to make space for the spring element and then moves back when the end of the spring element is in position, thus preventing a possible vertical return movement of the end of the spring element.

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, each of the grid sections including outer straps flatly facing the rods, each of the grid sections including main sleeves being positioned like positions of the same color in rows and columns disposed at right angles 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 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 circumference of one of the main sleeves, and spacer sleeves each being disposed between and rest

Abstract: Device for the spacing and holding in place of fuel rods arranged in accordance with a mesh network in a nuclear reactor, incorporating a spacing structure having recesses regularly arranged in accordance with a mesh network superimposed on the mesh network of the rods, cylindrical sleeves formed from rings connected by elastic strips curved towards the inside of each sleeve and means for fixing the sleeves to said structure.