Abstract: In a nuclear reactor fuel bundle assembly having a plurality of fuel rods and a non-round water rod extending between upper and lower tie plates, and having at least one fuel rod spacer located along the non-round water rod, an improvement which includes cooperating components on the fuel rod spacer and on the water rod for permitting movement of the spacer along the water rod to a desired axial location and for thereafter preventing further axial movement of the spacer in at least one of two opposite axial directions, the cooperating components including at least one spring on one of the spacer and the water rod.

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: 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: A method of repairing a nuclear fuel rod assembly having a damaged fuel rod and/or a damaged spacer cell.

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: A fuel assembly avoiding the generation of irradiation damage, a Zr alloy used for the same, and a manufacturing method thereof. According to one embodiment, a super-saturated solid-solution Zr alloy powder having a crystal grain size in the range of 1000 nm or less and containing Fe, Ni and Cr is prepared by mechanical alloying, and the alloy powder is subjected to HIP, hot-working, cold-working and final heat-treatment.

Abstract: A method for mitigating crack initiation and propagation on the surface of metal components in a water-cooled nuclear reactor. An electrically insulating coating doped with a noble metal is applied on the surfaces of IGSCC-susceptible reactor components. The preferred electrically insulating material is yttria-stabilized zirconia doped with palladium or platinum. The presence of an electrically insulating coating on the surface of the metal components shifts the corrosion potential in the negative direction without the addition of hydrogen. Corrosion potentials .ltoreq.-0.5 V.sub.SHE are believed to be achievable even at high oxidant concentrations and in the absence of hydrogen, although the coatings are believed to be particularly suited to applications where a reductant, such as hydrogen, is present.

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 boiling water reactor fuel assembly with fuel rods having variable fuel rod pitches.

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.

Abstract: A pressurized water nuclear reactor pressure vessel has an upper core support plate with passageways for the passage of coolant, an upper support plate above the upper core support plate, and peripheral hollow support columns extending upwardly above the passageways in the upper core support plate for supporting the upper support plate above the upper core support plate and for guiding coolant from the passageways into the plenum. Each peripheral support column has a peripherally slotted upper portion for guiding the coolant in the peripheral support column into the plenum and an unslotted lower portion.

Abstract: A spacer for retaining nuclear fuel rods in laterally spaced relation to one another includes first and second sets of spacer strips extending in mutually perpendicular diagonal directions relative to a generally rectilinear peripheral spacer band. The strips have linearly extending sections with adjacent sections angularly related to one another and meeting at apices. The sections of each strip alternately intersect a diagonal line across the spacer with the apices alternately located on opposite sides of the diagonal line. Alternate apices have springs projecting to one side of the strip for engaging fuel rods and apices between the alternate apices have stops projecting on opposite sides of the strip for engaging the fuel rods. Slots are provided in the strips enabling intermeshing of the strips with one another to define discrete cells peripherally encompassing and retaining fuel rods within the spacer.

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 nuclear fuel assembly for a pressurized water reactor having lower and upper tie plates, guide tubes, spacer grids, an instrumentation tube, and extended fuel rods which extend to the lower tie plate and which are spaced radially and supported along the guide tubes by the spacer grids, at least one of the extended fuel rods having at a lower end a fuel rod lower end cap secured by a first spring within an aperture in the lower tie plate and which exerts a lateral force against the lower end cap. The upper tie plate further includes a fuel rod support housing which extends down over the upper end of the at least one of the extended fuel rods and has a second spring positioned in a bore in the fuel rod support housing which exerts a lateral force on the upper end of the extended fuel rod positioned within the bore in the fuel rod support housing.

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 spacer for use with a fuel bundle in a nuclear reactor includes a matrix of ferrules for surrounding individual fuel rods within a bundle; a band surrounding the matrix and defining a peripheral wall of the spacer, the band having an upper edge; and a plurality of laterally spaced flow tabs extending upwardly from the upper edge, each flow tab having a lower substantially vertical portion and an upper inclined portion extending away from the vertical portion. The vertical portion and the inclined portion are formed with centrally located creases which define reverse bends in the upper and lower portions of the tab.

Abstract: A fixturing tool includes a sleeve having a central region with a circular axial opening and four leaf springs projecting from each of the opposite ends of the central region. The central region is cruciform in cross-section with arcuate side walls between the projections of the cruciform. Unit cells are arranged on a base having openings corresponding in location to the centers of the unit cells in their final assembly in a spacer for a nuclear fuel rod bundle. Fixturing devices are freely and loosely disposed within the unit cells and pins are partially inserted through the fixturing devices to expand the leaf springs to engage the unit cells. Once the cells with fixturing devices and partially inserted pins are centered over the base openings, the pins are advanced into the openings in the base to accurately align each unit cell relative to one another to enable final welding of adjacent cells to one another.

Abstract: A fuel bundle assembly for a boiling water nuclear reactor includes an open ended tubular channel subdivided into four quadrants by at least two interior partitions, each quadrant having a sub-fuel bundle assembly having a plurality of fuel rods extending between upper and lower tie plates. An inter-bundle support plate receives a lower end of the channel and has four flow openings at an upper end thereof, such that the lower tie plate of each sub-fuel bundle supported in a respective one of the openings in the support plate. In one embodiment, the sub-fuel bundles within a channel are separated by a cruciform shaped coolant passage. In a second embodiment, the cruciform coolant passage is omitted to thus provide a homogeneous sub-fuel bundle configuration.

Abstract: The lower tie plate grid includes cylindrical bosses and webs interconnecting the bosses for supporting nuclear fuel rods and defining flow openings through the grid. Coolant flows through the flow openings for flow upwardly about the fuel rods. The grid includes upper and lower portions and a screen is disposed between the upper and lower grid portions upon assembly with the bosses and webs of the respective upper and lower grid portions in registry with one another. The grid portions are welded to one another whereby the apertured screen serves to separate debris from the coolant flowing through the flow openings. The screen has openings in registry with the openings defined by the bosses for receiving the end plugs of the fuel rods.

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 reactor coolant debris filter for insertion within a nuclear fuel assembly support.

Abstract: Disclosed is a grid structure for supporting fuel rods in a nuclear reactor. The grid structure is formed of a plurality of interconnected thin metal grid straps that are welded or brazed together to provide a structural network of interconnected open grid cells, similar to an "egg crate divider". The grid straps are provided at regular intervals, corresponding to the width of a grid cell, with pairs of spaced, substantially horizontal, slotted spring-like projections and a substantially X-shaped spring-like projection vertically intermediate the horizontal projections. The spring-like projections are designed to support and hold the fuel rods within the grid cells under both balanced and unbalanced forces acting on the fuel rod assembly while it is in service, surrounded by coolant in the nuclear reactor.

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 nuclear fuel assembly for a boiling water reactor having a spacer grid for positioning and retaining the fuel rods. The spacer grid comprising an upper grid structure and a lower grid structure. Each grid structure comprises a first set of grid strips and a second set of grid strips which intersect to form in each grid structure a lattice of rectangular and square shaped cells through which the fuel rods extend and which act against the fuel rods within the cells. The lattice in each of the upper grid structure and the lower grid structure being the same. The upper grid structure and the lower grid structure being oriented relative to one another so that each of the rectangular and square shaped cells in the upper grid structure is superimposed on a corresponding one of the rectangular and square shaped cells in the lower grid structure so as to act cooperatively against and provide support to a fuel rod on four sides of the fuel rod.

Abstract: A spacer for retaining a number of elongated fuel rods into a bundle to be placed in a nuclear reactor of BWR or PWR type. The bundle is intended to be traversed in the longitudinal direction by a coolant. The spacer includes a number of cells for the fuel rods surrounded by an outer frame which is formed from a first band standing on edge. This band has possibly been extended by a skirt arranged on the upstream side of the spacer. The band or skirt edge of the spacer located on the upstream side thereof is provided with guiding tabs which are formed from plate flaps which lie in planes which extend in parallel with the flow direction of the coolant and one side edge of which slantingly extends from the first band or skirt edge in an upstream direction towards the center of the spacer.

Abstract: A second fuel rod positioned at each corner of a channel box and second fuel rods adjacent to the former are formed to have a smaller outer diameter than that of ordinary first fuel rods, so that a pitch between the second fuel rods is narrower than a pitch between the first fuel rods. Making the outer diameter of the second fuel rods smaller than that of the first fuel rods reduces the power per unit length of the second fuel rods. The narrower pitch between the second fuel rods than the pitch between the first fuel rods provides two effects. First, a unit lattice cell becomes so small as to avoid an increase in the H/U ratio. Secondly, a new moderator region is formed between the second fuel rods and the first fuel rods adjacent thereto, the moderator region acting to intensify thermal neutron flux around those first fuel rods. These two effects enable a further reduction in the power per unit length of the second fuel rods.

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: A rectilinear sectioned water rod--preferably of square cross-section--is provided with horizontal grooves for keying to bands on the inner, water rod surrounding aperture of spacers. Each spacer is constructed preferably of Inconel and includes a specialized inner band for keying to the water rod. The inner spacer member includes an upper surrounding band, a lower surrounding band, and four connecting vertical members--one positioned at each corner of the water rod. Two adjacent vertical members are bent inward to contact one side of the water rod at spaced apart points on the corners of the water rod. The remaining two adjacent vertical members are bent inward to contact the remaining two corners at single points on each vertical member.

Abstract: A cross point spacer is provided with subchannel vertical tubes at the subchannel volumes, these tubes being supplied with an inner flow free cylindrical volume and an peripheral steam separator in the form of a surface which imparts a spiral flow pattern to steam/water mixture flowing peripherally upwardly within the subchannel tube. According to a first and preferred embodiment, the subchannel tube of the cross point spacer is provided with rifling. According to a second embodiment, twisted vanes are installed and fastened to the interior of the subchannel tube and drilled away at the central portion of the twisted vanes to leave strips of metal defining rifling like paths on the subchannel tube interior. In either case, the main and central portion of the subchannel volume through the spacer is provided with an unobstructed central portion for upward steam flow.

Abstract: An apparatus for attaching a key member to a nuclear fuel assembly grid and detaching the same therefrom is disclosed. The apparatus includes a supply and recovery mechanism, an inserting and removing mechanism, and a rotating mechanism. The supply and recovery mechanism operates to supply the key member to a prescribed position adjacent to the grid and recover the same. The inserting and removing mechanism is disposed between the supply and recovery mechanism and the grid, and operates to insert the key member supplied from the supply and recovery mechanism into the grid and remove the key member from the grid to recover the same to the supply and recovery mechanism. The rotating mechanism is disposed adjacent to the inserting and removing mechanism, and operates to rotate the key member inserted in the grid in a prescribed direction about the longitudinal axis to attach the same to the grid and rotate the same in a direction opposite to the prescribed direction to detach the same from the grid.

Abstract: A nuclear fuel assembly grid (100) made from a plurality of interlaced corrugated metal strips (102-116) forming an egg-crate configuration so as to define plurality of four-walled cells (118) for receiving respective individual fuel rods (120). The spaced apart vertical bend lines (160,162) of the currugation define vertices (130,132) and consecutive body panels (164,166) which alternate generally inwardly and outwardly between consecutive bend lines. A vertical slot (168) extending from one of the strip upper or lower edges (176) into each panel midway between consecutive bend lines, and overlapping a slot from an interlaced strip to form an hourglass-shaped cell having opposed convex walls and opposed concave walls and four 90 degree corners (150). Spring (148) and stop (153) structure projects from each wall of a cell, for centering and supporting the fuel rod within the cell.

Abstract: Fuel assembly including deflector vanes for deflecting a component of a fluid stream flowing past such fuel assembly. The fuel assembly comprises a lattice member having rhombic-shaped rod cells and generally rhombic-shaped thimble cells therethrough. A plurality of parallel fuel rods extend through respective ones of the rod cells and a plurality of parallel control rod guide thimble tubes extend through respective ones of the thimble cells. A plurality of deflector vanes are associated with each rod cell and are integrally attached thereto on the upstream edge of each rod cell. Each deflector vane extends above its associated rod cell and curvilinearly protrudes partially over the rod cell for deflecting a component of the fluid stream onto the exterior surface of the fuel rod that extends through the rod cell.

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: A fuel assembly, where crystallographic orientations of a channel box are brought into a random distribution; and cladding tubes, spacers and a channel box are made from highly corrosion-resistant, Fe--Ni, zirconium-based alloy, hardened in the (.alpha.+.beta.) phase or .beta.-phase temperature region, has an average discharge burnup level of 50 to 550 GWd/t.

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 spacer for a nuclear reactor fuel assembly includes a cell-formed lattice-work for retaining parallel, elongated elements such as fuel rods (4) into a bundle of substantially square cross section. The cells are formed from tubular, preferably round sleeves (1). Each one of these offers a passage for one of the elements for mutually fixing these elements. Each spacer is formed from two sub-spacers (5) somewhat spaced-apart from each other in the longitudinal direction of the bundle. A first sub-spacer in a pair fixes elements lying substantially on one side of a diagonal through the bundle, and a second sub-spacer fixes the other elements such that elements passing through the sleeves (1) of the first sub-spacer pass, possibly with some exception, at the side of the sleeves in the second sub-spacer and vice versa.

Abstract: A flow deflector grid (10) for a nuclear fuel assembly, comprising a plurality of metal strips (12,14) which intersect in a regular array to form an egg-crate type lattice, which defines a plurality of coolant flow channels (16). Each channel has sidewalls (42,44) defined by the strips, a height dimension defined by the height of the strips, a plurality of corners (46) defined by the strip intersections (26), a channel central axis parallel to the height dimension, and a flow cross section normal to the channel axis for coaxially receiving a fuel rod (18) spaced within the channel sidewalls. A unitary flow deflector member (30) is attached to and situated in the corner of each channel so as to be cradled between first and second sidewalls.

Abstract: A low pressure drop spacer for positioning and retaining the fuel rods of a nuclear fuel assembly in which a plurality of upper and lower spring forks which extend through apertures in the side wall of the spacer into the assembly and through apertures in grid members which divide the assembly. The intersection and superposition of the spring forks, side wall and grid members form fuel rod passageways through which the fuel rods extend.

Abstract: A grid key for interior grid cells. A rectangular main body portion is bent near the middle at approximately a 90 degree angle. Two tabs that are flush with the main body portion extend outward in opposite directions from one end and along a portion of the length of the main body portion. The opposing side of the tabs is tapered at a 45 degree angle back toward the main body portion. The main body portion has a thickened section that coincides with the tabs. The thickened section is wedged between the soft stops of an individual interior grid cell to retract the stops and allow loading of a fuel rod.

Abstract: A nuclear fuel perimeter strip grid corner-piece (12) of increased flatness having at least two flat side sections (18,20) on either side of a transverse bend line (22) is provided. The flat side section (20) or sections (20 and 32) which have small cut-outs for arches (34), as opposed to large spring (36) cut-outs, as the fuel support features adjacent to the bend line (22) of variable radii at portions (24 and 26) are stress-relieved by means of slots (30) of length equal to 1/2 to 1/3 of the width of the flat section. The slot (30) is of a width less than twice the material thickness, so as not to weaken the structure near bend (22).

Abstract: In a fuel bundle for a boiling water nuclear reactor, modification of the spacers at the peripheral spacer band is made to maintain a more uniform spacing of the peripheral fuel rods from the channel walls to avoid critical power limitations. The conventional fuel bundle construction include a plurality of side-by-side sealed vertically disposed nuclear fuel rods in a square array supported at a lower tie plate, at least some of the fuel rods fastened to an upper tie plate, and held in designed spaced apart relation as a unitary mass by intermittent vertically placed spacers. A square sectioned channel surrounds the upper tie plate, the lower tie plate, and the fuel rods and spacers therebetween. The square sectioned channel functions to confined fluid flow interior of the fuel bundle between the tie plates and through the fuel rods. At the same time, the channel separates a core bypass region exterior of the channel having high moderator density from the flow path interior of the fuel bundle.

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: A spacer for retaining parallel, elongated fuel rods includes a plurality of cells which are formed from tubular sleeves internally provided with fixed supports and at least one spring arranged opposite to the fixed supports. The spring is intended to make contact with a fuel rod inserted into the sleeve and is formed as a leaf spring which is cut out of the wall of the sleeve and which, when the sleeve is empty, is bent into the sleeve. The leaf spring is adapted, in tensioned position when the fuel rod is inserted into the sleeve, to be returned to a position substantially coinciding with the wall of the sleeve.

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 fuel assembly grid (10) in which the height dimension of the grid strips (A,B,C,D) varies along the strip length, so that channels or cells (24',28) immediately surrounding the guide tube (30) define a relatively longer flow path, than channels that are relatively remote from the guide tube. In particular, the grids have a first plurality of four-walled first cells (24) for receiving and supporting respective fuel rods (26) and a second plurality of four-walled second cells (28) that are larger in cross-sectional area than, and interspersed among, the first cells, for receiving respective guide tubes (30). The improvement according to the present invention, provides that the height dimension (H2) of each strip (C) that defines walls of particular first and second cells is greater at the walls of the particular second cells, than at the walls of at least some of the particular first cells.