Abstract: A side-slotted nozzle type double sheet spacer grid for nuclear fuel assemblies is disclosed. The spacer grid includes intersecting inner strips and four perimeter strips. Each inner strip has unit strip parts, each fabricated by integrating two unit sheet parts together into a single structure, such that the two unit sheet parts face each other and a nozzle type coolant channel is defined between the two unit sheet parts. Each perimeter strip is fabricated by integrating an inner thin sheet having the unit sheet parts with a flat outer thin sheet having a width corresponding to the width of the inner thin sheet into a single structure. The coolant channel has one or more outlets formed by cutting an upper portion of one of the two unit sheet parts of each unit strip part. Each unit sheet part has a slot longitudinally formed on each side surface of a spring that is projected from the unit sheet part to support a fuel rod within a four-walled cell.

Abstract: A fuel assembly having a plurality of fuel rods arranged in a square lattice array. The fuel rods include a plurality of short-length fuel rods each having a fuel active length shorter than that of each of remaining ones of the fuel rods. At least one water rod is arranged in a region in which one or more of the fuel rods are arrangeable in the array, and a plurality of fuel spacers are provided at a plurality of positions in the axial direction for holding the plurality of fuel rods and the at least one water rod, with mutual radial intervals therebetween being kept immovable. The plurality of short-length fuel rods include at least one first short-length fuel rod arranged in the outermost peripheral region of the square lattice array. Each of the plurality of fuel spacers include a plurality of cylindrical members.

Abstract: A spacer grid for nuclear fuel assemblies is disclosed. This spacer grid has a plurality of side weld supports, that is, main supports, upper sub-supports and lower sub-supports, on its interlaced inner straps, with two flow mixing vanes integrally extending upward from each of the main supports. This spacer grid is fabricated by seam-welding the interlaced first and second inner straps to each other along the upper axial junction lines of the crossing main and upper sub-supports at the top of the intersections, and along the lower axial junction lines of the crossing lower sub-supports at the bottom of the intersections, thus forming side weld lines at the intersections.

Abstract: A spacer grid for use in a nuclear fuel assembly has double-deflected vanes that guide an axial flow of coolant around fuel rods and thereby generate swirl flow. The vanes each have a double bend projecting upwardly from first inner straps and projecting toward one fuel rod. The vanes are sufficiently wide at their bases to prevent inadvertent deformation due to contact with fuel rods during an insertion of fuel rods into the cells. The vanes also make a smooth variation in the cross-sectional area of the coolant channel at the outlet of the spacer grid, thus reducing a loss of pressure during reactor operation.

Abstract: A fuel element for a nuclear reactor has fuel rods with nuclear fuel guided through spacers. The spacers are equipped with devices that exert a swirling impulse upon a coolant flowing along the fuel rods. In order to present as little flow resistance as possible for the coolant, these swirl-introducing devices have the form of a vane with a spoonlike or bladelike shape and they extend into the coolant flow. Owing to the shape—here the vane is curved in the longitudinal and in the transverse directions—practically all cross sections of the vane have such a high geometrical moment of inertia that even a vane made of a thin sheet metal is sufficiently rigid. Fuel elements configured according to the invention are particularly suitable for use in boiling water nuclear reactors.

Abstract: A spacer grid for use in a nuclear fuel assembly has double-deflected vanes that guide an axial flow of coolant around fuel rods and thereby generate swirl flow. The vanes each have a double bend projecting upwardly from first inner straps and projecting toward one fuel rod. The vanes are sufficiently wide at their bases to prevent inadvertent deformation due to contact with fuel rods during an insertion of fuel rods into the cells. The vanes also make a smooth variation in the cross-sectional area of the coolant channel at the outlet of the spacer grid, thus reducing a loss of pressure during reactor operation.

Abstract: A double strip mixing grid for nuclear reactor fuel assemblies is disclosed. This grid is fabricated by intersecting at right angles a plurality of double strips, each fabricated by welding two thin sheets together into a single structure with coolant channels. The mixing grid, having the channels, effectively mixes low temperature coolant with high temperature coolant within a fuel assembly, thus improving the thermal efficiency of the fuel assemblies. This mixing grid also effectively prevents the coolant from being partially overheated, thus improving the soundness of nuclear reactors. This mixing grid also has swirling flow blades and/or lateral flow blades to further improve the thermal efficiency of the fuel assembly. This mixing grid elastically supports the fuel rods by the sheets of the double strips, collaterally acting as positioning springs.

Abstract: A fuel assembly attains high burnup and increases reactor shut-down margin when loaded into a reactor core wherein a water gap width on a control rod side and a water gap width on a side opposite to the control rod side are almost equal to each other. The fuel assembly has a plurality of fuel rods arranged in a square lattice pattern, each fuel rod being filled with nuclear fuel pellets and also has at least one neutron moderator rod shifted toward one corner where a control rod is inserted, away from a cross sectional center of the fuel assembly.

Abstract: A core inlet structure for coolant disposed in a reactor pressure vessel of a boiling water reactor includes a core support plate provided with a plurality of fuel support holes, a reinforcing beam supporting the core support plate, a plurality of control rod guide pipes standing perpendicularly and having upper end portions fitted to the fuel support holes, and a fuel support member inserted into upper end portions of the control rod guide pipes and supported by the core support plate so as to support lower end portions of fuel assemblies. An inlet orifice is formed to the fuel support member so as to adjust flow rate of a coolant flowing in the fuel assemblies, and a vortex control structure is provided for the inlet orifice or provided at a portion on a coolant upstream side of the inlet orifice.

Abstract: A duct-type spacer grid for nuclear fuel assemblies is disclosed. In this spacer grid, a plurality of duct-shaped grid elements, individually having an octagonal cell, are closely arranged in parallel and are welded together, thus forming a matrix structure. The grid elements do not pass across the center of the subchannel of the assembly, thus effectively reducing pressure loss. Each of the grid elements is formed as an independent cell, and so they effectively resist against a lateral impact. A plurality of integral type swirl flow vanes, having different heights or same height, axially extend from the top of the grid to be positioned within each subchannel. The swirl flow vanes are bent outwardly, and so they do not contact the fuel rods during an insertion of the fuel rods into the cells. In the spacer grid, the fuel rods are supported within the cells by line contact springs without using any dimple.

Abstract: In a boiling water fuel assembly, some of the fuel rods are shortened. It is necessary to establish a sufficiently high maximum power for transition to boiling. To optimize this power, spacers are at a constant distance at a bottom and are at a shorter distance at a top. The spacers belonging to upper group have turbulence-generating vanes which, however, do not project above the shortened fuel rods.

Abstract: Water rod segments are provided in a nuclear fuel bundle and releasably connected one to the other at joints within openings through the spacers. A lowermost water rod segment passes through a number of the spacers, with water rods segments above the lowermost segment being screwthreaded one to the other forming joints therebetween within the spacer openings. Capture flanges are provided immediately above and below the spacers on each of the segments such that the spacer is captured between adjoining segments. Interior passages through the segments communicate water along the water rod to an upper region of the fuel bundle. Swirler vanes are disposed about the water rod segments and terminal ends of the swirler vanes may form the capture flanges, retaining the spacer between adjacent segments.

Abstract: A spacer grid with hybrid flow-mixing devices for nuclear fuel bundle is made up of an intersection of a plurality of thin straps at right angles to form a plurality of cells for receiving and supporting fuel rods. Each strap is composed of two types of strap units, called a primary strap unit and a secondary strap unit, which are alternately arranged along the strap. The primary strap unit is a strap section having a primary vane set, and a secondary strap unit is a strap section having a secondary vane set. The straps intersect such that, by primary and secondary strap units, each intersection forms a hybrid flow-mixing device around the top of each junction. The primary vane set, consisting of a trapezoidal primary vane stand and two bent primary mixing vanes on both sides, protrudes upwardly from the strap and is primarily for generating cross flow between channels.

Abstract: A support grid for laterally maintaining the relative position of elongated fuel elements within a fuel assembly for use within a core of a nuclear reactor. The grid is formed in the shape of a lattice with the intersecting lattice members defining a plurality of cells, most of which respectively support the nuclear fuel elements. The remaining cells support nuclear control rod guide tubes and instrumentation thimbles. The cells supporting the nuclear fuel elements are provided with diagonally positioned springs on two, adjacent walls. The springs support the fuel elements against dimples which protrude from the opposite cell walls. The adjacent, diagonal springs in each fuel element cell are inclined in opposite directions. The walls of the cells supporting the control rod guide tubes are embossed along their height at the locations intermediate the intersection between adjoining walls with a concave notch having a curvature which conforms to the outside surface curvature of the control rod guide tubes.

Abstract: A spacer grid for PWR assemblies is characterized by curved flow channels between adjacent fuel rods and straight, essentially flat strips connecting opposite side plates of the spacer. The latter strips prevent bowing-out of the side plates during fuel assembly fabrication and during operation in the reactor. Additionally, the spacer grid allows accurate positioning of the fuel rods on a square lattice with a precisely defined pitch, and support of the rods in their spacer cells is such that rod bow will be minimized. The direction of the nozzles on the flow channels has been chosen to promote cross-flow of the coolant through the assembly.

Abstract: The invention relates to a fuel assembly for a boiling water reactor which is adapted, during operation of the reactor, to allow water to flow upwards through the fuel assembly while absorbing heat from a plurality of fuel rods, whereby part of the water is transformed into steam. The fuel assembly comprises a steam channel through which the steam flows through the fuel assembly. The steam channel (16a, 16b, 16c, 16d) consists of an empty volume which at least extends through part of the fuel assembly. The fuel assembly is designed such that the water and the steam are brought to rotate around the steam channel whereby the water is thrown away from the steam channel whereas the steam which is separated from the water flows upwards through the steam channel.

Abstract: A fuel assembly includes a plurality of fuel rods placed in a square lattice array of 9-rows/9-columns and at least one water rod. In this fuel assembly, the fuel rod pitch of the plurality of fuel rods is in a range of 14.15 mm to 14.65 mm, and means for offsetting and holding a fuel bundle composed of the fuel rods and the water rod is provided in such a manner that the center in a cross section of the fuel bundle is offset from the center in a cross section of the lower tie plate toward the channel fastener side. With this configuration, it is possible to provide a fuel assembly for a D-lattice core, which is capable of achieving the fuel economy comparable to that of a C-lattice core without reducing the thermal margin, and of using the existing fuel spacers.

Abstract: A flow diverter is provided for attachment to a spacer cell above a part-length fuel rod. The flow diverter includes a tubular base having a plurality of laterally projecting tabs extending in an upstream direction for diverting flow from between the spacer cells into the volume above the spacer void of a fuel rod. A vortex generator is secured to or forms an integral part with the flow diverter for swirling the flow onto and into the interstices of laterally adjacent fuel rods. The flow diverter and vortex generator are formed of tubular stock. The vanes of the vortex generator are formed by providing slits along the tubular stock and twisting alternating edges of the stock inwardly to form the vanes.

Abstract: A fuel bundle assembly for a boiling water nuclear reactor comprising a plurality of fuel rods having respective fuel columns therein, and arranged in an ordered array, extending between upper and lower support structures, the plurality of fuel rods enclosed within a hollow, open-ended channel member at least partially enclosed by the open-ended channel member; at least one water rod supported on the lower tie plate and extending upwardly toward the upper tie plate, the at least one water rod having an upward flow path including at least one inlet at a lower end of the upward flow path, and a downward flow path including at least one outlet at a lower end of the downward flow path, the at least one outlet located about midway along the fuel columns within the fuel rods.

Abstract: A fuel assembly for a boiling water reactor which is designed to allow water, during operation of the reactor, to flow upwards through the fuel assembly while absorbing heat from a plurality of fuel rods, whereby part of the water is transformed into steam. The fuel assembly comprises a first steam pipe (10a) arranged with its longitudinal axis parallel to the longitudinal axis of the fuel assembly and the steam pipe comprises an inlet for the steam arranged in the first end of the steam pipe and an outlet for the steam arranged in the second end of the steam pipe. The fuel assembly also comprises a second steam pipe (10b) arranged above and at a distance from the first steam pipe such that an opening is formed between the steam pipes. The outlet of the first steam pipe has a diameter which is larger than the diameter of the inlet of the second steam pipe.

Abstract: A duct-type spacer grid for nuclear fuel assemblies is disclosed. In this spacer grid, a plurality of duct-shaped grid elements, individually having an octagonal cell, are closely arranged in parallel and are welded together, thus forming a matrix structure. The grid elements do not pass across the center of the subchannel of the assembly, thus effectively reducing pressure loss. Each of the grid elements is formed as an independent cell, and so they effectively resist against a lateral impact. A plurality of integral type swirl flow vanes, having different heights or same height, axially extend from the top of the grid to be positioned within each subchannel. The swirl flow vanes are bent outwardly, and so they do not contact the fuel rods during an insertion of the fuel rods into the cells. In the spacer grid, the fuel rods are supported within the cells by line contact springs without using any dimple.

Abstract: A nuclear fuel spacer grid, fabricated by intersecting a plurality of zircaloy or inconel grid strips and used for placing and supporting a plurality of elongated fuel rods within a nuclear fuel assembly, is disclosed. In the spacer grid of this invention, each of the grid strips is not cut away to form separate springs or dimples for supporting the fuel rods, but has an axial slot extending from one end of each strip to a length. The grid strips are intersected at the slots prior to being welded together into a single grid structure at a welding tap formed at an outside end or a middle portion of each of the slots. Each of the grid strips also has a dipper-shaped coolant mixing vane, or a dipper vane, at each of the upper and lower ends thereof. The spacer grid thus maximizes the thermal hydraulic coolant mixing effect within a fuel assembly and stably supports the fuel rods within the assembly while improving the mechanical/structural strength of the assembly, such as a buckling strength.

Abstract: The invention concerns a spacer (14) for a nuclear boiling water reactor. The spacer (14) comprises a plurality of cells (16) for holding or allowing elongated elements (12) to pass through the cells. Between the cells (16) there are a plurality of flow channels (18). The spacer comprises at least a plurality of deflecting members (22). The deflecting member comprises a vane (24) which extends in a direction from a cell (16) into the neighbouring flow channel (18). The vane is inclined relative to a vertical plane (26) and is wider in its upper part than in its lower part. The invention also concerns a fuel assembly for a nuclear boiling water reactor, comprising a deflecting member with vane of similar construction.

Abstract: A fuel assembly, particularly, a fuel assembly including short-length fuel rods and fuel spacers, is used for a boiling water reactor, which is capable of sufficiently reducing the pressure loss of at least one of the fuel spacers positioned above the upper ends of the short-length fuel rods, irrespective of the arrangement of the short-length fuel rods, and also ensuring the structural strength of the fuel spacer. The fuel assembly includes fuel rods located in a square lattice array, two water rods arranged in a region in which seven of the fuel rods are arrangeable, two fuel spacers for holding the fuel rods and the water rods with mutual intervals kept immovable. Each of the fuel spacers includes cells which are connected to each other and in which the fuel rods are to be inserted, respectively, and a band for surrounding the outermost peripheries of the cells. The short-length fuel rods include four first short-length fuel rods arranged in the outermost peripheral region of the square lattice array.

Abstract: A duct-type spacer grid for nuclear fuel assemblies is disclosed. In this spacer grid, a plurality of duct-shaped grid elements, individually having an octagonal cell, are closely arranged in parallel and are welded together, thus forming a matrix structure. The grid elements do not pass across the center of the subchannel of the assembly, thus effectively reducing pressure loss. Each of the grid elements is formed as an independent cell, and so they effectively resist against a lateral impact. A plurality of integral type swirl flow vanes, having different heights or same height, axially extend from the top of the grid to be positioned within each subchannel. The swirl flow vanes are bent outwardly, and so they do not contact the fuel rods during an insertion of the fuel rods into the cells. In the spacer grid, the fuel rods are supported within the cells by line contact springs without using any dimple.

Abstract: The present invention relates to a fuel assembly for a light-water reactor with a substantially square cross section wherein the fuel assembly comprises a plurality of fuel rods (4). The fuel rods (4) extend between a bottom tie plate (5) and a top tie plate (6) and a coolant is adapted to flow upwards through the fuel assembly. At least one of the top tie plates (6) or the bottom tie plates (5) comprises flow openings (22, 22a, 22b) for the passage of the coolant and side supports (17) for supporting the fuel rods (4) in the lateral direction. The side supports (17) are designed in one and the same sheet-metal piece as the flow openings (22, 22a, 22b) and the side supports (17) are folded substantially 90° in relation to the other structure of the top tie plate (6) or the bottom tie plate (5).

Abstract: A fuel assembly for a boiling water reactor comprising a plurality of fuel units, stacked on top of each other, each of which comprising a plurality of fuel rods extending vertically between a top tie plate and a bottom tie plate, and means for keeping the fuel elements together. The fuel elements are surrounded by a fuel channel with a substantially square cross section. At least two of the fuel units differ from each other in regard to fuel distribution or free flow area.

Abstract: A nuclear fuel assembly grid has a plurality of mutually interleaved straps forming an array of fuel rod receiving cells. Each strap is formed with regularly distributed slots for interleaving with other straps of the grid. The strap has dimples located between some at least of the slots for maintaining fuel rods in the cells. An uptstream portion of the plate extending in transverse relation to a coolant flow direction has a double sided concave chamfer.

Abstract: The present invention relates to a fuel assembly for a light-water reactor with a substantially square cross section wherein the fuel assembly comprises a plurality of fuel rods (4). The fuel rods (4) extend between a bottom tie plate (5) and a top tie plate (6) and a coolant is adapted to flow upwards through the fuel assembly. At least one of the top tie plates (6) or the bottom tie plates (5) comprises flow openings (22, 22a, 22b) for the passage of the coolant and side supports (17) for supporting the fuel rods (4) in the lateral direction. The side supports (17) are designed in one and the same sheet-metal piece as the flow openings (22, 22a, 22b) and the side supports (17) are folded substantially 90° in relation to the other structure of the top tie plate (6) or the bottom tie plate (5).

Abstract: An improved support grid of a nuclear reactor fuel assembly is described. The support grid has a plurality of first and second straps which are assembled so as to form an eggcrate structure defining grid cells in a square arrangement. The support grid includes a plurality of mixing vanes integrally formed on a side edge of the first and second straps adjacent to an area where the straps cross. The mixing vanes slanted to be adjacent to a fuel rod are each shaped to show no welding apertures formed therein in their horizontal planes of projection thereby maximizing the coolant impinging area to agitate and swirl a coolant flow.

Abstract: A nuclear fuel spacer grid, fabricated by intersecting a plurality of grid strips and used for placing and supporting a plurality of elongated fuel rods within a nuclear fuel assembly, is disclosed. The spacer grid of this invention has a plurality of dimple vanes on its grid strips. The dimple vanes are designed to guide the coolant from one cell to neighboring cells of the spacer grid, thus accomplishing a desired coolant mixing effect and increasing the thermal allowance of the fuel rods and accomplishing a high performance fuel assembly. The spacer grid also has a multi-spring structure, consist in of one arc-shaped main spring and two bow-shaped sub-springs. The main spring directly supports the fuel rod within the spacer grid, while the sub-springs have the same radius of curvature as that of the external surface of the fuel rod and effectively support the fuel rod when the main spring fails to support the fuel rod.

Abstract: A fuel assembly for a nuclear reactor is described, the fuel assembly including: a plurality of fuel pins (12) extending substantially parallel to the axis of the assembly and to each other; at least two structural grids spaced apart from each other, the grids being in contact with said fuel pins (12) and maintaining said fuel pins substantially mutually parallel and preventing contact therebetween, wherein the fuel assembly further comprises at least one mixing grid (50) situated intermediate said at least two structural grids, the fuel assembly being characterized in that said mixing grid (50) is positioned and fixedly located out of substantial contact with said fuel pins (12), the mixing grid also having turbulence inducing means (61) to promote turbulence in a coolant (62) flowing through said fuel assembly in use and in that the mixing grid is formed from sheet metal wherein the plane of the metal sheet from which the mixing grid is formed lies in a plane which is transverse to the axis of the fuel pin

Abstract: The invention relates to a fuel assembly for a boiling water reactor which is adapted, during operation of the reactor, to allow water to flow upwards through the fuel assembly while absorbing heat from a plurality of fuel rods, whereby part of the water is transformed into steam. The fuel assembly comprises a steam channel through which the steam flows through the fuel assembly. The steam channel (16a, 16b, 16c, 16d) consists of an empty volume which at least extends through part of the fuel assembly. The fuel assembly is designed such that the water and the steam are brought to rotate around the steam channel whereby the water is thrown away from the steam channel whereas the steam which is separated from the water flows upwards through the steam channel.

Abstract: A fuel assembly spacer grid including swirl deflectors respectively arranged at interconnections between interconnecting longitudinally and laterally-extending straps on upper ends of the interconnecting straps adapted to support fuel elements of a nuclear fuel assembly. Each of the swirl deflectors has four vanes bent to have an air vane shape. By virtue of this configuration, an improvement in the efficiency of the spacer grid cooling the fuel elements. The spacer grid also includes springs each configured to generate not only a main spring force caused by a displacement of the spring occurring when the spring comes into contact with a fuel element placed in a reactor core, but also an additional spring force caused by hydraulic pressure applied to the spring. Each spring, which is in a fixed state at one end thereof, has a free bent portion at the other end.

Abstract: A fuel bundle assembly for a boiling water nuclear reactor comprising a plurality of fuel rods having respective fuel columns therein, and arranged in an ordered array, extending between upper and lower support structures, the plurality of fuel rods enclosed within a hollow, open-ended channel member at least partially enclosed by the open-ended channel member; at least one water rod supported on the lower tie plate and extending upwardly toward the upper tie plate, the at least one water rod having an upward flow path including at least one inlet at a lower end of the upward flow path, and a downward flow path including at least one outlet at a lower end of the downward flow path, the at least one outlet located about midway along the fuel columns within the fuel rods.

Abstract: A support rod 14 carrying one or more separation devices 12, e.g., swirlers, is releasably secured in a fuel bundle. The support rod and separation devices are sized to pass through openings in the spacers S otherwise containing full length fuel rods. The lower end of the support rod is releasably connected to the upper end of a part-length fuel rod PLR which in turn is releasably connected to the lower tie plate. The support rod, separation devices and part-length rod may be installed and removed relative to the fuel bundle as an integral assembly with the part-length rod and separation devices passing through the openings in the spacers. When installed, the separation devices lie above upper spacers in the vent volumes to flow liquid on and into the interstices of the surrounding fuel rods.

Abstract: A grid with coolant deflecting channels for used in nuclear fuel assemblies is disclosed. In the grid, two sets of intersecting grid strips are arranged in sets at right angles to each other prior to being encircled by four perimeter strips, thus forming a plurality of four-walled cells individually placing and supporting an elongated fuel rod therein. Each of the grid strips is made up of two narrow sheets which are deformed at a plurality of regularly spaced portions to provide nozzle-type coolant deflecting channels. The channels individually have an upright Y-shaped or reversed Y-shaped configuration capable of so deflecting coolant as to mix low temperature coolant with high temperature coolant. The channels thus form a uniform temperature distribution within a fuel assembly. The channels are so inclined with respect to the axes of the fuel rods as to form wide and linear positioning springs at middle portions thereof.

Abstract: A spacer for retaining and positioning elongated elements at one or a plurality of levels in a nuclear reactor fuel assembly comprises a grid structure of joined-together sleeve cells. A coolant is adapted to flow upwards through the fuel assembly. The majority of the sleeve cells are provided with an upstream edge with a waveform. The edge is waveformed in such a way that the upwardly flowing coolant first encounters a peak of the wave which is disposed between the joints of the sleeves and thereafter a valley of the wave which is disposed at the joints of the sleeves. The peaks are arranged closer to a center of the sleeve cell than the valleys. Between the peaks and valleys, oblique edges are formed.

Abstract: A swirler is releasably attached to a spacer and lies in the opening through the spacer lying above a part-length fuel rod in a nuclear fuel bundle. Adjacent ferrules have upstanding tabs with loops forming part of connecting elements for releasably securing the swirler to the spacer. The spacer is mounted on a mounting ring having radially outwardly directed elements terminating in barbed ends for insertion through the loops in response to rotation of the swirler mounting ring relative to the tabs. The barbed ends can be squeezed together to release the swirler from its attachment with the spacer.

Abstract: A spacer including a plurality of cells to retain and mutually fix parallel, elongated elements, extending through the cells, in a bundle in a fuel assembly for a nuclear reactor where a coolant is adapted to flow from below and upwards. Between the cells, secondary channels are formed. At least one of the spacers includes at least two deflection members being substantially arranged so as to be surrounded by the cells. The deflection members are axially spaced-apart in the direction of flow of the coolant and relative to each other at a pitch angle for stepwise axial and radial deflection and guiding of at least part of the coolant flow towards fuel rods included in the bundle. The fuel rods are arranged close to the secondary channels.

Abstract: A protection flap provided on mixing vanes of structural or mid-span mixer grids in order to eliminate or substantially reduce fretting of fuel rods retained by such grids. The flap is an extension or addition of vane material bent upwardly so as to be substantially parallel to the longitudinal axis of the fuel rod being retained. The flap provides a smooth, vertical surface against which the fuel rod contacts in case of vibration, bowing or shifting.

Abstract: A nuclear fuel core in a pressurized-water reactor including fuel assemblies, each of which comprise a top tie plate; a bottom tie plate, the top tie plate and the bottom tie plate having through-openings for passing coolant flowing from beneath upwards through each of the fuel assemblies; elongated elements, arranged between the top tie plate and the bottom tie plate; a mixing cross section having a mixing center, the mixing cross section extending through four orthogonally arranged fuel assemblies and having a size corresponding to at least that of two fuel assemblies; and a plurality of spacers for retaining and mutually fixing the elongated elements, the plurality of spacers having flow control members for controlling coolant flow around the mixing center. A nuclear fuel core in a boiling water reactor is also disclosed.

Abstract: The spacer comprises a plurality of strips interleaved with one another to form an eggcrate-type pattern defining essentially rectilinear cells for each fuel rod. Each strip includes a central body portion with cantilevered loop spring-like projections extending to opposite sides, with spring contact portions projecting inwardly. Stops are provided along each of the central body regions of the strips intermediate the loop springs that project to the opposite side of the strip. Adjoining walls have loop spring portions for biasing the rod into engagement with opposing stops whereby each fuel rod is supported at six contact points, i.e., four spring contact points and two hard stop contacts opposite the paired spring contacts.

Abstract: The invention relates to a fuel assembly (1) and a spacer (7) for a nuclear reactor wherein the spacer comprises a plurality of cells (9) for retaining and mutually fixing parallel elongated elements (3, 8) extending through the cells to form a bundle in the fuel assembly. The cells are tubular and internally provided with four elongated, non-independently resilient supports (10), formed in the sleeve material, or with two elongated, non-independently resilient supports (10), formed in the sleeve material, and two independently resilient supports (16), wherein the supports are intended to provide an all-sided positioning of the elongated element. (FIG.

Abstract: An arrangement of fuel rod support members having dimples and springs is presented to prevent abrasive wear of the fuel rods caused by bouncing of the fuel rods against the supporting members caused by vibrations in a diagonal direction of the support grids. The supporting members are disposed such that dimples are respectively provided on one pair of adjacent walls located on one side of the vibrational direction while springs are respectively provided on adjacent walls located on the opposite side of the vibrational direction.

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 fuel assembly for use in a pressurized water nuclear reactor includes an assembly having guide tubes joined at their upper ends to posts having heads against which is biased a holddown plate spaced from a flow plate. The holddown plate is slidably mounted on the posts. The flow plate is fixed to the posts. The joints have one either post or tube member with spring fingers with projecting steps to lock in abutting relation behind the flow plate with a ring projection on the other captured in a recess in the adjacent finger surfaces. This structure provides a quick connect joint between the tube and the post.

Abstract: In a fuel bundle for a boiling water nuclear reactor comprising a plurality of fuel rods (20) secured within an array and extending between upper and lower tie plates (24, 22), and including at least one additional partial length fuel rod (20') extending from said lower tie plate (22) but terminating short of said upper tie plate (24), an improvement in the form of a removable extension rod (32) secured to said at least one additional fuel rod (20') and extending substantially to said upper tie plate (24). The removable extension rod (32) also permits variance in the reactivity of the partial length fuel rod (20') particularly in the two phase region of the bundle (10).

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: Triangular lattice for LWR square fuel assemblies.