Abstract: A nuclear reactor core mechanical support bracket is disclosed. The support bracket includes a housing, a spring disposed internally within the housing, a shaft slidingly disposed within the housing, a shaft travel pin, and a flange. The shaft is configured to engage the spring to compress and decompress the spring as the shaft travels in and out of the housing. The shaft travel pin controls the travel of the shaft. The flange is configured to mount the nuclear reactor core mechanical support bracket to a canister of a nuclear reactor. The shaft includes an inset configured to interface with a nuclear reactor core component.

Abstract: An apparatus for controlling movement of a first component integrated with a second component may include a first clamp configured to engage the first component, a second clamp configured to engage the second component, and a plurality of connectors configured to connect the first and second clamps. The connectors may allow movement of the first clamp relative to the second clamp in a first direction between the first and second clamps. The connectors may limit movement of the first clamp relative to the second clamp in a second direction perpendicular to the first direction.

Abstract: The pressurized water reactor according an embodiment comprises: a cylindrical reactor pressure vessel (1) to which inlet nozzles are connected; fuel assemblies which are contained within the reactor pressure vessel (1); a cylindrical reactor core barrel (3) which surrounds the fuel assemblies and forms an annular downcomer (6) between the reactor core barrel (3) and the inner surface of the reactor pressure vessel (1); and radial supports. The radial supports are supports which are arranged below the downcomer (6) at intervals in the circumferential direction, each has vertical flow path formed therein, and position the reactor core barrel (3) and the reactor pressure vessel (1). The radial supports each has, for example, a flow path-equipped radial keys (21) and a key groove member (40).

Abstract: A method and apparatus for repairing and/or preventatively maintaining a jet pump restrainer assembly used in a Boiling Water Reactor (BWR), the repair including attaching a bearing plate or plates to a horizontal surface of a jet pump restrainer assembly bracket, the bearing plate or plates acting to supplement and/or replace an existing contact surface between a mixer wedge and the jet pump restrainer assembly bracket of a jet pump restrainer assembly.

Abstract: Nuclear reactor systems and methods are described having many unique features tailored to address the special conditions and needs of emerging markets. The fast neutron spectrum nuclear reactor system may include a reactor having a reactor tank. A reactor core may be located within the reactor tank. The reactor core may include a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium. A pump may circulate the liquid sodium through a heat exchanger. The system may include a balance of plant with no nuclear safety function. The reactor may be modular, and may produce approximately 100 MWe.

Abstract: A core shroud is provided, which includes a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners. Each unitary corner comprises a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion. At least one of the subassemblies comprises a plurality of the unitary corners disposed side-by-side in an alternating opposing relationship. A plurality of the subassemblies can be combined to form a quarter perimeter segment of the core shroud. Four quarter perimeter segments join together to form the core shroud.

Abstract: A method to confine a nuclear reactor fuel bundle assembly including: inserting a lower portion of the fuel bundle assembly into an open end of a lower fuel particle barrier; supporting the lower portion of the fuel bundle with the lower fuel particle barrier; grasping the lower portion of the fuel bundle assembly with the lower fuel particle barrier; lowering an upper fuel particle barrier over an upper tie plate of the fuel bundle assembly; moving at least a portion of a handle fixed to the upper tie plate through an open slot in the upper fuel particle barrier; closing the open slot with a closure device after the handle passes through the slot, and preventing fuel particles being released from the nuclear reactor fuel bundle assembly by the upper and lower fuel particle barriers.

Abstract: A nuclear reactor fuel bundle confinement system including: a fuel bundle with an upper tie plate; a channel enclosing the fuel bundle; a handle for the fuel bundle extending above the fuel bundle; an upper fuel particle barrier positioned over the upper tie plate and above the fuel rods, wherein the fuel particle barrier has a permeable panel at least co-extensive with an open area of the upper tie plate; a slot in the permeable panel through which passes the handle, and a closure device on the fuel particle barrier having a closed position which covers the slot and an open position that leaves the slot open; a lower fuel particle barrier positioned over the lower tie plate and below the fuel rods, wherein the lower portion of the fuel bundle assembly is grasped by the lower fuel particle barrier.

Abstract: A nuclear reactor includes a reactor pressure vessel 12 and a core barrel 14, contained within the reactor pressure vessel 12. The reactor 10 further includes a single vertical support 16, for transmitting vertical load from the core barrel to the reactor pressure vessel. Further, lateral support means is provided at an elevation which is above that of the support 16 to provide lateral support to the core barrel 14. This arrangement will result in reduced stress arising from the temperature fluctuations.

Abstract: Nuclear reactor systems and methods are described having many unique features tailored to address the special conditions and needs of emerging markets. The fast neutron spectrum nuclear reactor system may include a reactor having a reactor tank. A reactor core may be located within the reactor tank. The reactor core may include a fuel column of metal or cermet fuel using liquid sodium as a heat transfer medium. A pump may circulate the liquid sodium through a heat exchanger. The system may include a balance of plant with no nuclear safety function. The reactor may be modular, and may produce approximately 100 MWe.

Abstract: A plate mounted fuel assembly hold-down system that provides a defined channel for both the insertion and removal of reactor head mounted, fixed in-core detector instrumentation, provides a guided path for the fixed in-core detector during insertion, and shields the instrument shroud against coolant cross flow. The hold-down assembly includes a base plate that seats on the adapter plate of the fuel assembly and has openings that align with the control rod guide thimbles. A hollow sleeve extends through and below a central opening in the base plate to mate with the fuel assembly instrument thimble. The sleeve extends above the base plate and through and above an upper core plate of the reactor. A hold-down bar is slidably mounted on the sleeve and is restrained below the top of the sleeve. A spring is positioned around the sleeve and is captured between the hold-down bar and the base plate.

Abstract: The invention concerns a method for repairing guide rails (27) of an assembly (10) radially maintaining a core supporting plate (5), which consists in measuring the spacing between the spans of the lateral branches of the guide rail (27) to be repaired, cutting and removing at least one lateral branch of said guide rail (27) to be repaired, measuring the dimensions of said lateral branch and machining with identical dimensions at least one substitution lateral branch, mounting and fixing said substitution lateral branch and measuring the spacing between the spans of the lateral branches of the repaired guide rail.

Abstract: An embodiment of the present invention may reduce the level of vibration experienced by a line, such as, but not limiting of, a pipe, a cable, tubing, or the like, that is connected to at least one separate structure. For example, but not limiting of, the structure includes: a reactor pressure vessel, a feedwater sparger pipe, steam generator, a pipe, a pressure vessel, a heat exchanger, a pump, a condenser, a tank, or the like. An embodiment of the present invention may provide support and a preload to the line at a new location or may replace an existing support, such as, but not limiting of, a weld; which may alter the natural frequencies to avoid resonance from occurring when the structure(s) is excited.

Abstract: A core shroud is provided, which includes a number of planar members, a number of unitary corners, and a number of subassemblies each comprising a combination of the planar members and the unitary corners. Each unitary corner comprises a unitary extrusion including a first planar portion and a second planar portion disposed perpendicularly with respect to the first planar portion. At least one of the subassemblies comprises a plurality of the unitary corners disposed side-by-side in an alternating opposing relationship. A plurality of the subassemblies can be combined to form a quarter perimeter segment of the core shroud. Four quarter perimeter segments join together to form the core shroud.

Abstract: A method is provided for removing radioactive internals structural members in the core of a reactor pressure vessel in a containment vessel. The method includes placing a first cask in a first internals assembly, detaching radioactive first internals structural members from second internals structural members in the first internals assembly, placing the detached first internals structural members in the first cask, placing the first internals assembly in a second cask, and removing the second cask containing the first internals assembly and containing the casked detached radioactive first internals members from the containment vessel. The first internal members may be radioactive baffle plates, and the second internals members may be former plates bolted to the radioactive baffle plates. Novel tooling, framework and fixtures facilitate disassembling, moving and storing the radioactive baffle plates.

Abstract: The tie rod repair apparatus includes a tie rod secured at its upper end to the shroud flange at the top of the shroud. The lower end of the tie rod passes through an opening in the shroud support plate without imposing a load on the plate. The lower end of the tie rod is anchored to the lower end of the core shroud support cylinder such that the compressive load path exerted by the tie rod to restrain the cracked shroud passes directly through the shroud support cylinder and the assembly of shroud cylinders bypassing the shroud support plate.

Abstract: A clamp assembly connects a diffuser adapter or lower ring to a diffuser tail pipe of a jet pump diffuser in a boiling water nuclear reactor. The clamp assembly includes at least two clamp segments shaped generally corresponding to an exterior circumference of the diffuser, a swivel link affixed at each end of each of the clamp segments, and at least two connecting bands pivotably secured to the swivel links between the ends of the clamp segments. The clamp segments each includes a locking assembly engageable with the diffuser adapter or lower ring and the diffuser tail pipe. The clamp assembly structurally replaces/repairs the weld joining the diffuser adapter or lower ring and the diffuser tail pipe.

Abstract: A method of preventing separation of a feedwater sparger end bracket assembly comprises installing first and second clamp members of a clamp over a feedwater sparger end bracket assembly in opposition to one another, and leaving the clamp in place to constrain the feedwater sparger end bracket assembly against separation in first, second and third directions.

Abstract: A jet pump diffuser weld repair device includes a lower ring section and an upper ring section respectively sized to fit around a circumference of the diffuser on opposite sides of the weld to be repaired. The lower and upper ring sections are provided with a plurality of aligned gripper slots. A corresponding plurality of grippers are fit into the gripper slots, where at least one of the gripper slots and the grippers defines cam surfaces shaped to drive the grippers radially inward as lower and upper ring sections are drawn toward each other. A plurality of connector bolts are secured between the lower ring section and the upper ring section. Tightening of the connector bolts draws the lower and upper ring sections toward each other.

Abstract: An unirradiated nuclear fuel assembly transport canister that includes a clamshell type fuel assembly inner liner that has interior dimensions that closely conform to the outer envelope of the fuel assembly to be transported and exterior dimensions that conform to a generic overpack tubular container. The liner is inserted into the overpack tubular container which is in turn supported by a shock absorbing suspension system within a birdcage frame.

Abstract: A forged upper shroud section which may be machined from a single piece rectangular cross-section ring forging and includes a circular flange and a cylindrical shell is described. Openings and slots are machined into the flange to align and support the shroud head. A groove is machined along an inside surface of the cylinder section, and the groove may be used to support top guide grid (not shown). An end of the cylinder section is machined with a weld prep for attachment to the core section of the shroud.

Abstract: A repair apparatus for a shroud in a nuclear reactor pressure vessel is described. The repair apparatus includes an upper stabilizer assembly, a lower stabilizer assembly, and a tie rod configured to extend between and to couple to the upper and lower stabilizer assemblies. The upper stabilizer includes a stabilizer block and an upper stabilizer wedge slidably coupled to the upper stabilizer block. The upper stabilizer block is configured to couple to a shroud lug. The upper stabilizer wedge includes an integral leaf spring portion formed by a slot in the wedge and is configured to engage the side wall of the reactor pressure vessel. The lower stabilizer assembly includes a stabilizer block and a lower stabilizer wedge slidably coupled to the lower stabilizer block. The lower stabilizer block is configured to engage the shroud. A horizontal stabilizing spring is attached to the wedge and is configured to engage the side wall of the reactor pressure vessel. The tie rod is threaded at each end.

Abstract: An electrode discharge machining (EDM) apparatus for machining slots in a jet pump diffuser in a nuclear reactor pressure vessel is described. The apparatus is configured to machine a plurality of slots in the diffuser at positions behind the diffuser sensing line within the plane formed by the center of the diffuser and the sensing line. The apparatus includes a housing, a plurality of clamp assemblies, a hook assembly configured to engage the sensing line standoff so that the apparatus is positioned at an angle from a plane formed by the center of the diffuser and the sensing line, and a plurality of electrode assemblies. The EDM apparatus can be configured to be installed clockwise or counter-clockwise around the sensing line depending on the spacing available around given diffusers. The EDM apparatus is capable of burning a plurality of slots at the same time, thereby saving time and money.

Abstract: A shroud attachment assembly which provides both structural support for the shroud and a seal between the shroud and shroud support is described. In one specific embodiment, the shroud attachment assembly includes a shroud flange formed integral with the shroud, and a pump deck flange formed integral with the pump deck. The shroud flange extends over the pump deck flange, and a plurality of studs extend through aligned openings in the flanges. In addition, a plurality of wedges are secured to the shroud flange by studs, and the wedges extend between the shroud flange and the pump deck flange. Generally, the studs which extend through aligned openings in the shroud and pump deck flanges transfer vertical loads from the shroud to the pump deck, and the wedges transfer horizontal loads from the shroud to the pump deck.

Abstract: An apparatus for repairing the core shroud of a nuclear reactor having one or more cracked vertical seam welds. The repair involves machining two holes in the shroud on opposing sides of the cracked vertical seam weld and then attaching two flexible links on the inside and outside of the shroud wall by means of two shear bolts inserted in the machined holes. The flexible links bridge the cracked vertical weld seam. Multiple link assemblies can be placed along the length of a crack. The links are made of an alloy having a coefficient of thermal expansion less than the coefficient of thermal expansion of the shroud material. The links are installed while the reactor is shutdown. When the reactor returns to operation, the consequent temperature rise causes the shroud section being bridged by the links to expand more than the links expand. As a result the links exert a circumferential compressive load across the crack in the vertical seam weld.

Abstract: A nuclear reactor vessel has a baffle-barrel assembly for supporting the fuel assemblies in its core region and guiding coolant flowing through the core region when the reactor vessel is in service. The baffle assembly includes a baffle plate fastened to a former plate by a bolt. The baffle plate has a countersunk hole extending to a smaller diameter baffle plate hole. The former plate has a bolt hole aligned with the baffle plate hole. The bolt has a head portion disposed in the countersunk hole and a shank extending from the undersurface of the head portion into the aligned bolt holes and threadedly engaged with the former plate.

Abstract: A mid-shroud joint which improves the replaceability of the shroud is described. In one embodiment, the shroud includes a core shroud and a lower shroud. A core plate support flange is clamped between the core shroud and the lower shroud, and the core plate support flange supports a core plate. The mid-shroud joint is formed by a flange of the core shroud and a flange of the lower shroud. The core plate support flange is positioned between core shroud and lower shroud flanges, and openings in these flanges align so that bolts can be inserted through such aligned openings.

Abstract: A shroud including an integral track for mounting inspection and cleaning tooling is described. In one embodiment, the shroud includes substantially cylindrical first and second shroud sections having a main body with a first end and a second end. One shroud first end has a weld prepared surface. Each shroud section includes a ledge in an exterior surface adjacent the first end. A weld is formed between the weld prepared surface and the first end of the second shroud section. At the weld, the shroud is substantially geometrically balanced with equal material on both sides of the weld. A geometrically balanced weld provides the same heat sink characteristics on both sides of the weld, and allows for a more uniform distribution of weld residual stresses.

Abstract: A core barrel for a reactor pressure vessel of a nuclear reactor plant has a carrying structure that is supported on an inner surface of the shroud of the barrel. The carrying structure receives a tension rod that extends parallel to the longitudinal axis of the barrel and braces the shroud in the axial direction.

Abstract: Support assemblies for allowing RPV radial expansion while simultaneously limiting horizontal, vertical, and azimuthal movement of the RPV within a nuclear reactor are described. In one embodiment, the support assembly includes a support block and a guide block. The support block includes a first portion and a second portion, and the first portion is rigidly coupled to the RPV adjacent the first portion. The guide block is rigidly coupled to a reactor pressure vessel support structure and includes a channel sized to receive the second portion of the support block. The second portion of the support block is positioned in the guide block channel to movably couple the guide block to the support block.

Abstract: An apparatus for repairing a shroud in which one or more seam welds are cracked. The repair involves the attachment of a splice bracket to the shroud so that the bracket bridges the cracked weld seam and is applicable to both vertical and horizontal weld seams. The bracket is intended to structurally replace the shroud seam weld which is cracked. Multiple splice brackets can be placed along the length of a crack. Each splice bracket is attached to the shroud by a plurality of tapered fastener assemblies.

Abstract: An apparatus and method are provided for replacing the existing lower internal components in a nuclear reactor vessel with new components. The alignment of the new lower internals to the pressure vessel and the existing upper internals is achieved by customizing the new lower internals on-site based on alignment measurements obtained by gages installed on the new core barrel and the existing upper core plate. The gages allow the custom machining of radial support keys on the lower portion of the new core barrel and the custom drilling of upper core plate alignment pin holes in the new core barrel.

Abstract: A method of replacing a boiling water reactor core shroud includes the steps of removing at least a portion of the existing core shroud from supporting structure in the reactor vessel, lowering a replacement shroud into the reactor vessel, positioning the replacement shroud on the supporting structure such that a bottom portion of the replacement shroud mates cooperatively with the supporting structure to limit lateral movement of the replacement shroud relative to the reactor vessel, and holding the replacement shroud assembly in place by applying axially compressive forces to the shroud in the direction of the supporting structure. If the existing core shroud is secured by welds, a parting cut is made to remove the shroud and the replacement shroud is held in place by securing a plurality of tie rods between sites on the replacement shroud and the supporting structure at a respective plurality of angularly spaced locations about the shroud periphery.

Abstract: In a nuclear reactor including a reactor vessel and a core shroud disposed within the reactor vessel in laterally spaced relation, a seismic support includes a spacer extending between laterally opposed surfaces of the reactor vessel and the core shroud to limit lateral movement of the core shroud relative to the reactor vessel and a deformable member carried by the spacer and having a configuration to deform substantially elastically in response to impacts caused by an operating basis earthquake and substantially plastically at relatively constant load in response to impacts caused by a design basis earthquake. The deformable member can be carried at an end of the spacer adjacent the reactor vessel or between the spacer and a bearing plate, and can be formed of a material having a yield strength less than that of the spacer and/or be of reduced cross-sectional area as compared with the spacer to yield under a desired seismic load.

Abstract: In a pressure vessel of a nuclear reactor containing a core assembly enclosed within a core shroud, the core shroud spaced radially inwardly of a pressure vessel wall, with an annular shroud support plate fixed to the pressure vessel wall, wherein a lower end of the shroud is seated on an upper edge of the support plate to create a joint interface further wherein, and a plurality of brackets are secured between the shroud and the shroud support plate, spanning the joint interface.

Abstract: In order to support a shroud against bending, shear, stress and torsion, straps are placed in strategic positions with respect to cracks or like types of weaknesses which have been detected, and fastened in place using a suitable fastening technique. Holes are formed using an EDM technique in cooperation with supports for an EDM placed on the straps, and bolt units which have an expanding portion are inserted into the holes, torqued and expanded in a manner which fastens the strap to the shroud. A temperature responsive bimetallic strain system which produces a clamping force, is created by forming the straps of a material which has a lower expansion coefficient than the shroud material. As the reactor heats, the expansion differential tensions the straps and produces a clamping force.

Abstract: In order to support a shroud against bending, shear, stress and torsion, straps which are preferably formed of the same material as the shroud, are placed in strategic positions with respect to cracks or the like type of weaknesses which have been detected, and fastened in place using a suitable fastening technique. In the preferred embodiments of the invention holes are formed using an EDM technique and bolt units which have an expanding portion are inserted into the holes, torqued and expanded in a manner which fastens the strap to the shroud. Welding and the like type of fastening techniques are not excluded and may used alternatively or in combination with the bolting technique as required.

Abstract: The device (15) for joining together a first plate (7) and a second plate (8)of the baffle assembly, which are located substantially at right angles, includes a screw (16) engaged in a housing consisting of an opening (18) passing through the first plate (7), and of a tapped blind opening (20) in the second plate (8). At least one opening (21) places an annular space (18b) around the shank (16b) of the screw in communication with the entry part (18a) of the opening (18) passing through the first plate (7), in order to deconfine the screw (16). The opening (21) may be a radial opening passing through a cup (17) against which the screw head (16a) comes to bear or an opening machined in the first plate (7) against a shoulder (18c) of the screw housing and the part (18b) of the opening for passing through the first plate (7) in which the shank (16b) of the screw (16) is engaged.

Abstract: An apparatus for stabilizing a shroud against vertical and lateral deflection. The apparatus forms a vertical load path by which the shroud flange can be anchored to the shroud support plate. In the tensioned state, an upper support assembly exerts a restraining force on the top surface of the shroud flange which opposes separation of the shroud at any assumed failed circumferential weld location. The apparatus further incorporates upper and lower restraint springs which oppose lateral deflection at the elevation of the top guide support ring and at the elevation of the core plate support ring respectively. The vertical restraint assembly is made of material having a coefficient of thermal expansion which is less than a coefficient of thermal expansion of the shroud material. A desired differential thermal expansion of the vertical restraint assembly and the shroud can be attained by the selection of member lengths and materials having appropriate coefficients of thermal expansion.

Abstract: An apparatus for repairing the core shroud of a nuclear reactor having one or more cracked vertical seam welds. The repair involves installation of a ring around the circumference of the shroud while the reactor is shutdown. The ring is tensioned with a mechanical preload and then vertically supported with shear bolts or struts. The ring is made of an alloy having a coefficient of thermal expansion less than the coefficient of thermal expansion of the shroud material. When the reactor returns to operation, the consequent temperature rise causes the shroud to expand more than the ring expands. As a result the ring exerts a circumferential compressive load across any cracks in the vertical seam welds intersected by the ring.

Abstract: Core shrouds are conventionally welded together from cylindrical parts and annular flanges, wherein cracks have recently occurred in the region of weld seams in reactors of the boiling-water type. A core shroud, in particular for cladding a reactor core in a boiling-water nuclear reactor and a method for repairing a core shroud, include recesses disposed transversely relative to the circumferentially extending weld seams. The recesses have a middle part which passes through a region that is thermally influenced during welding as well as transverse grooves or widenings located in front of ends of the middle part and lying outside the thermally influenced region. A clamp which is fitted into the recess is disposed approximately flush with a shroud surface and is wedged in one of the transverse grooves.

Abstract: Methods and apparatus for maintaining a compression force in a reactor pressure vessel (RPV) of a nuclear reactor are described. In one embodiment of the apparatus, a spring assembly facilitates applying compression force on the shroud head. The spring assembly, in one embodiment, includes two trusses and two torsion bars. The torsion bars extend between the trusses and are connected at opposite ends to the trusses. Each truss includes a truss support member, a hooking element, and a torsion converter element. The truss support member is configured to rest on the shroud head flange. The hooking element is pivotally coupled to the truss support member, and includes a hook adjacent a guide rod. The torsion converter element is coupled to the hooking element, and is vertically movable with respect to the truss support member. The converter element has two ends, each end splined to one of the torsion bars so that vertical movement of the converter element drives, e.g., rotates, the torsion bars.

Abstract: A method of replacing a boiling water reactor core shroud includes the steps of removing at least a portion of the existing core shroud from supporting structure in the reactor vessel, lowering a replacement shroud into the reactor vessel, positioning the replacement shroud on the supporting structure such that a bottom portion of the replacement shroud mates cooperatively with the supporting structure to limit lateral movement of the replacement shroud relative to the reactor vessel, and holding the replacement shroud assembly in place by applying axially compressive forces to the shroud in the direction of the supporting structure. If the existing core shroud is secured by welds, a parting cut is made to remove the shroud and the replacement shroud is held in place by securing a plurality of tie rods between sites on the replacement shroud and the supporting structure at a respective plurality of angularly spaced locations about the shroud periphery.

Abstract: An apparatus for repairing a shroud in which one or more seam welds are cracked. The repair involves the attachment of a splice bracket to the shroud so that the bracket bridges the cracked weld seam and is applicable to both vertical and horizontal weld seams. The bracket is intended to structurally replace the shroud seam weld which is cracked. Multiple splice brackets can be placed along the length of a crack. Each splice bracket is attached to the shroud by a plurality of tapered fastener assemblies.

Abstract: In a pressure vessel of a nuclear reactor containing a core assembly enclosed within a core shroud, the core shroud spaced radially inwardly of a side wall of the pressure vessel with an annular pump deck located in an annular radial space between the core shroud and the side wall of the pressure vessel, the improvement wherein the shroud is removably secured to an annular support leg extending upwardly from the bottom of the pressure vessel; and further wherein the annular pump deck is provided in the form of a plurality of removable segments.

Abstract: In order to support a shroud against bending, shear, stress and torsion, straps which are preferably formed of the same material as the shroud, are placed in strategic positions with respect to cracks or the like type of weaknesses which have been detected, and fastened in place using a suitable fastening technique. In the preferred embodiments of the invention holes a formed using an EDM technique and bolt units which have an expanding portion are inserted into the holes, torqued and expanded in a manner which fastens the strap to the shroud. Welding and the like type of fastening techniques are not excluded and may used alternatively or in combination with the bolting technique as required.

Abstract: A method and an apparatus for stabilizing a shroud against lateral deflection. The shroud restraint stabilizer has springs which exert radially inwardly directed forces that resist lateral deflection of the shroud relative to the reactor pressure vessel. Each stabilizer includes a stabilizer preload spring and a seismic restraint spring. Each spring has resilient arms integrally connected to opposing ends of a common main support span. The resilient arms of the stabilizer preload spring form a first leaf spring of relatively lower stiffness and the resilient arms of the seismic restraint spring form a second leaf spring of relatively higher stiffness. The different stiffnesses are achieved by providing the first leaf spring with a longer base than that of the second leaf spring. The pads on the seismic restraint spring are in contact with the reactor pressure vessel, but are not preloaded under operating conditions. The seismic restraint spring is loaded in response to lateral deflection of the shroud, e.g.

Abstract: A method and apparatus for repairing nuclear reactor core shrouds having horizontal cracks in heat affected zones of welds joining a horizontal plate to upper and lower cylindrical sections of the shroud includes securing a plurality of braces between an upper shroud flange and a top surface of the horizontal plate near an inner edge of the plate. The braces are installed at a respective plurality of angularly spaced locations within the upper cylindrical section of the shroud and each have an upper notched end for bearing against a bottom edge of the flange and a lower notched end for bearing against the top surface of the horizontal plate and/or an outer peripheral edge of an upper core grid structure mounted on the top surface of the plate.

Abstract: A method and apparatus for repairing nuclear reactor core shrouds includes applying vertical compressive forces to the shroud in situ to urge opposed ends of the shroud toward one another using a plurality of tie-rods, each including a plurality of coaxial longitudinal members separated by a radial gap filled with reactor coolant or some other damping fluid. One of the longitudinal members is secured to upper and lower portions of the shroud for maintaining a sufficient preload to hold the shroud together and is coupled with one or more other longitudinal members in a manner to transmit axial loads thereto upon extending a predetermined axial distance. A plurality of radial spacers can also be positioned at longitudinally spaced locations along the length of the tie-rod to assure control rod insertion by limiting lateral movement of the shroud and can reduce the preload required for preventing the formation of new cracks and stabilizing existing cracks.

Abstract: An apparatus, which reinforces a shroud that is contained within a reactor vessel, is operable for reinforcement of the shroud in the event of cracking in the shroud. The apparatus comprises a reactor wall positioned surrounding the shroud. A beam is attached to and extends generally axially on the shroud for absorbing the forces generated by the cracking in the shroud, and a radial support is positioned between the beam and the wall of the reactor vessel for transmitting any forces absorbed by the beam to the wall.