Abstract: A prefabricated in-core nuclear plant instrumentation chase concrete form is provided that has integral embedment plates at the locations where the in-core instrumentation guide thimble supports contact the walls of the chase. Structural steel shapes are located on the outside of the prefabricated chase at the embedment locations to transfer loads on axially-spaced, transverse, thimble support plates that route and support guide thimbles through which the in-core instrumentation pass, into the surrounding concrete structure. The guide thimble supports are installed in the pre-fabricated chase form at the factory and serve to strengthen the structure during shipping and handling as well as resist the loads applied by the wet concrete poured around the prefabricated chase during installation at a nuclear plant site.

Abstract: An integrated head assembly (100) is disclosed for a nuclear reactor. The preferred integrated head assembly includes a lift assembly (150) that supports the reactor vessel closure head (90) and integrated head assembly for removal, a separate support structure (202) supported by a ring beam (151) that sits atop the reactor vessel closure head, a shroud assembly (200), a seismic support system (300), a baffle assembly (500), a missile shield (400), and a CRDM cooling system. The CRDM cooling system draws cooling air into the baffle assembly, downwardly past the CRDMs (96), outwardly to upright air ducts (600), upwardly to an upper plenum (680), and out of the assembly through the air fans (190).

Abstract: A method and system for thermal-dynamic modeling and performance evaluation of a nuclear Boiling Water Reactor (BWR) core design is presented. A data processing system is used to execute specific program routines that simultaneously simulate the thermal operating characteristics of fuel rods within the reactor during a transient operational condition. The method employs a multi-dimensional approach for the simulation of postulated operational events or an anticipated operational occurrence (AOO) which produces a transient condition in the reactor—such as might be caused by single operator error or equipment malfunction. Based on a generic transient bias and uncertainty in the change in critical power ratio (&Dgr;CPR/ICPR), histograms of fuel rod critical power ratio (CPR) are generated.

Abstract: A reactor servicing platform for a nuclear reactor is provided. The nuclear reactor includes a reactor pressure vessel positioned in a primary containment and at least one refuel bridge. The primary containment includes a refueling floor. The servicing platform, in an exemplary embodiment, includes a frame, a support structure, and a floor covering the frame. The floor includes a reactor access opening sized to permit access to the reactor pressure vessel.

Abstract: A method and a device are provided for monitoring a power rise during startup of a nuclear reactor (diversitary excursion monitoring). In order to be able to shut down the reactor during startup in the event of prompt critical states, a power band situated in a lower measuring range is prescribed for a signal of power range channels which detects the reactor power in the power range. Startup is continued only when the signal does not exceed an upper limit within a minimum time, after the last occasion of exceeding a lower limit of the power band.

Abstract: When carrying the large structure out through an aperture portion provided at a roof of a reactor building, a chamber for covering the aperture is provided at the roof so that work of providing the chamber for covering the aperture portion can be performed independent of other work performed in the reactor building, before at least a part of work of using a roof crane and at least a part work of handling fuel assemblies in the reactor building.

Abstract: When carrying the large structure out through an aperture portion provided at a roof of a reactor building, a chamber for covering the aperture is provided at the roof so that work of providing the chamber for covering the aperture portion can be performed independent of other work performed in the reactor building, before at least a part of work of using a roof crane and at least a part work of handling fuel assemblies in the reactor building.

Abstract: An opening portion 3 is produced by cutting a recirculating piping 72 connected to a recirculating nozzle 2 of a reactor pressure vessel 1. A repairing device is brought into an annulus 10 of the reactor pressure vessel 1 from the opening 3, thereby repairing the annulus 10.

Abstract: An apparatus and method for maximizing the radiation shielding for spent nuclear fuel during cask transfer procedures. In one aspect, the method comprises submersing an apparatus having a jacket and a cavity for receiving spent nuclear fuel into a pool, wherein the jacket is empty and hermetically sealed; placing spent nuclear fuel into the cavity of the apparatus; lifting the apparatus from the pool; placing the apparatus in a staging area; filling the jacket with neutron absorbing liquid; draining the pool water from the cavity; and lifting the apparatus from the staging area.

Abstract: Methods for cutting a labyrinth seal in a nuclear reactor jet pump assembly are described. In one embodiment, the method includes removing an irradiated jet pump inlet mixer from the jet pump assembly, positioning the jet pump inlet mixer underwater, and cutting at least one circumferential groove in an inlet mixer outside surface.

Abstract: Methods for cutting a labyrinth seal in a nuclear reactor jet pump assembly are described. In one embodiment, the method includes removing an irradiated jet pump inlet mixer from the jet pump assembly, positioning the jet pump inlet mixer underwater, and cutting at least one circumferential groove in an inlet mixer outside surface.

Abstract: The neutron monitoring system measures neutrons by counting both the negative pulse signals and the positive noise pulse signals output from a neutron detector 1, and subtracts the positive pulse count from the negative pulse count per unit time, thereby measuring the neutrons.

Abstract: A neutron absorber system for a nuclear fuel storage rack includes a neutron absorber, which is adapted to attach to a plurality of cell walls of a cell of the nuclear fuel storage rack. The neutron absorber is adapted to elastically deform to cause the attaching. A system for inserting a neutron absorber into the nuclear fuel storage rack includes means for applying at least one stress to the neutron absorber and means for releasing the at least one stress to cause the neutron absorber to attach to the plurality of cell walls of the cell of the nuclear fuel storage rack.

Abstract: There are provided a control rod holding unit 16 for releasably holding a control rod 7 which is loaded in a reactor vessel 1, and fuel support/control rod guide tube holding unit 17 for releasably holding a fuel support 8 which supports a bottom end of a fuel assembly 10 and a control rod guide tube 6 on which the fuel support 8 is placed at top end. The control rod holding unit 16 and the fuel support/control rod guide tube holding unit 17 are fitted to a main body frame 26 which can be hoisted down inside the reactor vessel 1. Accordingly, there can be provided a reactor-internal equipment handling apparatus and method which are capable of reducing a term of work which is required for operations to load/unload the control rods, the fuel supports, and the control rod guide tubes.

Abstract: An old core shroud (11) and an old jet pump (16) received in a reactor pressure vessel (1) are cut and carried out. A module of core internals having a new core shroud (N11), a new jet pump (N16) and a new baffle plate (N29) integrated is carried into the reactor pressure vessel (1) in which an old baffle plate (28) and an old shroud support cylinder (13) welded and fixedly secured to the reactor pressure vessel (1), and an old shroud support leg (12) fixedly secured to said old baffle plate (28) and said old shroud support cylinder (13) are left. Then, the new baffle plate (29) is fixedly secured to the old baffle plate (28), and the new core shroud (11) is fixedly secured to the old shroud support leg (12).

Abstract: An integrated head assembly (100) is disclosed for a nuclear reactor. The preferred integrated head assembly includes a lift assembly (150) that supports the reactor vessel closure head (90) and integrated head assembly for removal, a separate support structure (202) supported by a ring beam (151) that sits atop the reactor vessel closure head, a shroud assembly (200), a seismic support system (300), a baffle assembly (500), a missile shield (400), and a CRDM cooling system. The CRDM cooling system draws cooling air into the baffle assembly, downwardly past the CRDMs (96), outwardly to upright air ducts (600), upwardly to an upper plenum (680), and out of the assembly through the air fans (190).

Abstract: A non-steady state computer model of water in a Boiling Water Reactor (BWR) primary water flow circuit is used to represent the water chemistry and noble metal loading during, for example, an in situ noble metal application process. The modeling software is provided on a laptop or portable computer for real-time use in the field at different reactor sites. After inputting data representing the initial state of reactor water chemistry and operating conditions of the reactor, the model determines the water chemistry, pH, conductivity and noble metal loading throughout the BWR primary water flow circuit, including selected sample locations, as a function of time. Results are used to determine whether technical specifications on conductivity or other chemistry-related parameters will be exceeded during the noble metal application process. Values of rate constants used for modeling noble metal reactions may be changed on site at the reactor during the application process.

Abstract: A container body of a concrete cask includes a storage portion that stores a canister. A refilling system includes a reduction cylinder having an outside diameter smaller than the diameter of the storage portion and an inside diameter larger than the diameter of the canister, a first lift mechanism configured to raise and lower the reduction cylinder between a down position in the storage portion and an up position wherein it is drawn out of the storage portion, and a second lift mechanism having a holding portion for holding one end portion of the canister and configured to raise and lower the canister with respect to the container body. In refilling operations, the canister is loaded into and unloaded from the storage portion of the container body by the second lift mechanism with the reduction cylinder set in the storage portion.

Abstract: One of methods for carrying out a reactor vessel according to the present invention comprises the steps of removing an overhead traveling crane in a reactor containment vessel of a pressurized water reactor, or the steps of, in an area where an overhead traveling crane is installed, operating the overhead traveling crane to move aside for creating a space, through which the reactor vessel is able to pass, and then carrying out the reactor vessel through an opening provided in a top portion of the reactor containment vessel. With the present method, the reactor vessel of the pressurized water reactor can be carried out in a short time with high efficiency.

Abstract: An inspection apparatus for inspecting welds in a nuclear reactor jet pump includes a probe subassembly rotatably and linearly movably coupled to a frame structure configured to attach to a top flange of the reactor pressure vessel. The probe subassembly includes a plurality of probe arms pivotably coupled to a housing, with each probe arm including a sensor. The probe arms are pivotably movable between a first position where the probe arms are parallel to a longitudinal axis of the probe subassembly, and a second position where the probe arms are at an angle to the longitudinal axis of the probe subassembly. An insertion subassembly couples to the jet pump suction inlet. The insertion subassembly is sized to receive the probe subassembly and guide the probe subassembly into the jet pump through the jet pump suction inlet.

Abstract: A robotic inspection system for gas turbine combustion components includes an exterior manipulator for visual inspection of the exterior surface of the impingement sleeve, an interior manipulator for visual inspection of the interior of the transition piece body and an annulus manipulator for inspecting the side weld seams of the transition piece body. The exterior manipulator includes an arcuate segment extending about the annular spaced impingement sleeves and a robotic subassembly including a linear rail and an upper arm and forearm mounting an inspection head pivotally coupled to one another for visual inspection of the top, bottom and side external surfaces of the impingement sleeve. The interior manipulator mounts to the open end of the combustion casing and includes an arm mounted for universal pivotal movement to the mount, actuators for pivoting the arm and motors for extending and rotating an inspection head about pan and tilt axes within the interior of the transition piece body.

Abstract: A water jet peening apparatus which can carry out an efficient peening work on a large-diameter cylindrical structure by injecting a jet stream which contains air bubbles caused by cavitation at a low angle of incidence is provided. The apparatus is comprised of a nozzle which introduces a high pressure water and injects a water jet stream containing air bubbles caused by cavitation at the cylindrical structure disposed in water, wherein the angle of injection of the jet stream is smaller than 45 degrees relative to a tangent of the cylindrical structure.

Abstract: The neutron monitoring system measures neutrons by counting both the negative pulse signals and the positive noise pulse signals output from a neutron detector 1, and subtracts the positive pulse count from the negative pulse count per unit time, thereby measuring the neutrons.

Abstract: A boiling water type nuclear reactor core, in which a plurality of fuel assemblies, each enclosed in a channel box, are loaded and a plurality of control rods, each having control blades, are arranged between the channel boxes. Long blade control rods, each having control rod blades which extend in four directions, are arranged between channel boxes on diagonals of square bundle regions each formed by a plurality of fuel assemblies, and short blade control rods, each having a control rod blade length of about half of the width of one of the square bundle regions, are arranged between the channel boxes in the center of each of the square bundle regions.

Abstract: A control rod/fuel support grapple is provided which is capable of pulling up simultaneously a control rod and a fuel support from a reactor and also uncoupling the control rod and control rod drive mechanism. The control rod/fuel support grapple comprises a control rod holding unit for holding a control rod's hoist handle, a fuel support holding unit for holding a fuel support, and a coupling releasing unit or uncoupling the control rod and the control rod drive mechanism, coupled by virtue of a spud coupling. These three units are attached to a main body frame which is lowered into a reactor pressure vessel.

Abstract: A storage/transport container for radioactive material has a metallic outer shell, a metallic inner shell concentrically received in the outer cell and defining therewith an annular space, and an annular and continuous heat-conductive meander strip in the space. The strip is formed unitarily with a plurality of angularly spaced inner segments engaging the inner shell, respective angularly spaced outer segments engaging the outer shell, and respective generally radially extending webs extending between the inner and outer segments.

Abstract: When a radioactivated reactor pressure vessel is carried out from a nuclear reactor building of a nuclear power plant, a first opening portion for carrying out the reactor pressure vessel is provided in a roof of the nuclear reactor building, a radiation shield for covering the reactor pressure vessel and shielding radiations is carried into the reactor building through the first opening portion, and installed on a reactor shield wall, lowering a hanger through the first opening portion and a slit provided on an upper lid of the radiation shield, a part of a lid of the reactor pressure vessel and a part of the upper lid of the radiation shield are abutted by hanging up the reactor pressure vessel by the hanger, and the reactor pressure vessel and the radiation shield integrated therewith are raised and carried out of the reactor building, whereby the shield can be easily mounted on the large-sized apparatus in a short time and a dose of radiations exposed to a worker when the shield is mounted can be reduced.

Abstract: A remotely installable piping support device includes a pair of mating tapered wedge segments extending from lever arms connected with a spiral wound spring. The spring is machined integrally with the left lever arm and has a projecting center square drive hub with an internal mounting thread. The right lever arm has an internal square drive which mates with the drive hub. A bolt engages the drive hub and secures the lever arms together. The spring preload on the wedge acting across the shallow angled wedge surfaces maintains rigid contact between jet pump components and takes up the clearance from wear during operation.

Abstract: A non-steady state computer model of water in a Boiling Water Reactor (BWR) primary water flow circuit is used to represent the water chemistry and noble metal loading during, for example, an in situ noble metal application process. The modeling software is provided on a laptop or portable computer for real-time use in the field at different reactor sites. After inputting data representing the initial state of reactor water chemistry and operating conditions of the reactor, the model determines the water chemistry, pH, conductivity and noble metal loading throughout the BWR primary water flow circuit, including selected sample locations, as a function of time. Results are used to determine whether technical specifications on conductivity or other chemistry-related parameters will be exceeded during the noble metal application process. Values of rate constants used for modeling noble metal reactions may be changed on site at the reactor during the application process.

Abstract: A boiling water reactor having a reactor pressure vessel with two recirculation loops hydraulically connected thereto is decontaminated by installing plugs in the outlets of jet pump ram's head manifolds located within the reactor pressure vessel to isolate the recirculation loops from the reactor pressure vessel. A monitoring gas is bubbled into some of the ram's head manifolds through the plugs to monitor the process pressure within the manifolds and riser pipes connected with the manifolds. The level of the decontamination solution in the riser pipes can be determined by determining the differential pressure due to the vertical height of the decontamination solution in the loops.

Abstract: A jacking device includes first, second, and third members (51, 52, 53), and a jacking screw (55). The first and second members (51, 52) have sloping side portions (57). The third member (53) has a plurality of sloped side portions (57) and a threaded opening (67) extending from its top portion (69) through to its bottom portion (59). The third member (53) is movably supported between the first and second members (51, 52). The jacking screw (55) engages the threaded opening (67) in the third member (53).

Abstract: A fuel rod extracting machine which can extract the fuel rods one by one from a Korean type 17×17 Light Water Reactor fuel assembly comprises a multi-functional rotary head including a camera for measuring the positions of the fuel rods and securing nuts being fastened on the bottom end piece of fuel assembly, an impact wrench for unfastening the securing nuts, and a gripper for gripping and extracting the fuel rods one by one. All of these are installed on a single rotary disc, which is driven by a tool rotating motor, at intervals of 90 degrees. To improve the reliability and safety in using the multi-functional rotary head, a load cell and a remote compliance center are installed at the rear of the gripper. The load cell monitors a state of insertion of the fuel rod into a collet and measures a fuel rod extracting force. The remote compliance center provides the smooth insertion of the fuel rod onto the collet, even though there exists a small misalignment between them.

Abstract: When a radioactivated reactor pressure vessel is carried out from a nuclear reactor building of a nuclear power plant, a first opening portion for carrying out the reactor pressure vessel is provided in a roof of the nuclear reactor building, a radiation shield for covering the reactor pressure vessel and shielding radiations is carried into the reactor building through the first opening portion, and installed on a reactor shield wall, lowering a hanger through the first opening portion and a slit provided on an upper lid of the radiation shield, a part of a lid of the reactor pressure vessel and a part of the upper lid of the radiation shield are abutted by hanging up the reactor pressure vessel by the hanger, and the reactor pressure vessel and the radiation shield integrated therewith are raised and carried out of the reactor building, whereby the shield can be easily mounted on the large-sized apparatus in a short time and a dose of radiations exposed to a worker when the shield is mounted can be reduced.

Abstract: The invention relates to a method of repairing the labyrinth seal of a diffuser in a primary pump, the diffuser being of the type comprising a peripheral skirt and a circular end wall having an orifice provided with the labyrinth seal. The method consists in making a bore in the circular end wall having a diameter greater than that of the orifice, in reducing the thickness of the remaining portion of the end wall, in forming a chamfer on the edge of the bore, in positioning a replacement part in said bore, the replacement part including a central orifice and a chamfer on its own peripheral edge, in making a bead of welding between the chamfers, and in making a new labyrinth seal in the central orifice of the replacement part.

Abstract: An apparatus for ultrasonically examining a weld in a nuclear steam supply system includes an elongated guide rod for positioning within a pipe of the nuclear steam supply system. An ultrasonic transducer is positioned at an end of the elongated guide rod. A collapsible shoe encloses the ultrasonic transducer. The collapsible shoe includes a biasing mechanism to allow the collapsible shoe to pass through the pipe while the pipe is at a first circumference and while the pipe is at a second circumference. The collapsible shoe continuously contacts the pipe to establish ultrasonic coupling for the ultrasonic transducer.

Abstract: A method of treating a large scale structural body is provided in which when carrying out and in the large scale structural body such as nuclear reactor pressure vessel and an internal reactor structural body from and to a nuclear reactor building, a used fuel pool and fuels stored inside thereof can be protected even if the large scale structural body drops by some cause. In the method of treating a large scale structural body in which an opening portion is provided at a roof of the nuclear reactor building and the large scale structural body is carried out/in through the opening portion; the carrying out/in of the large scale structural body is performed under a condition that a protective measure for the used fuel pool is provided in a nuclear reactor well.

Abstract: A sleeve assembly for refurbishing a fuel rack having cells in which fresh or spent nuclear fuel assemblies may be stored, in which the cells have elongate rack walls extending from a rack base plate and the rack base plate has flow holes communicating with the cells. The sleeve has at least one elongate wall extending from the topside of a sleeve base having an opposed bottom side. The sleeve base has a flow hole extending therethrough that communicates with one of the rack base plate flow holes. A pin assembly disposed in the sleeve base flow hole has resilient tabs extending beyond the bottom side of the sleeve base for extending into a rack base plate flow hole and resiliently engaging the rack base plate when the sleeve assembly is installed in one of the cells. The pin assembly resists horizontal and vertical movements of the sleeve assembly, permits water flow into the cell and permits sleeve assembly removal tools and inspection devices to access the pin assembly.

Abstract: A jet pump beam bolt locking assembly includes a locking sleeve having a plurality of ratchet teeth extending around the periphery of a base portion, and a lock plate having a beam bolt opening, and an integral beam spring arm having a plurality of ratchet teeth extending from at least a portion of a side of the spring arm. The spring arm ratchet teeth are sized to mesh with the locking sleeve ratchet teeth. The lock plate also includes a lip extending at least partially around the beam bolt opening which captures the locking sleeve. The spring arm is movable between a first position where a lock plate detent is positioned in a spring arm notch which permits engagement of the ratchet teeth, and a second position where the side of the spring arm is in contact with the detent which disengages the ratchet teeth to permit loosening of the beam bolt.

Abstract: A storage/transport container for radioactive material is made by first subdividing a chamber formed between an inner shell and an outer shell into first and second compartments by means of a foraminous partition having a predetermined maximum mesh size. Then an aggregate of a predetermined minimum particle size greater than the predetermined maximum mesh size is introduced into one of the compartments and a suspension of cement and water is introduced into the first compartment such that the aggregate remains in the one compartment and the cement and water flow through the partition into the second compartment. Normally the aggregate and the suspension are both introduced into the same compartment.

Abstract: A seal apparatus for a jet pump slip joint in a boiling water nuclear reactor pressure vessel, in an exemplary embodiment, includes a split seal ring and a segmented diaphragm spring engaging the split seal ring at an inner circumference of the diaphragm spring. The diaphragm spring includes a plurality of latch assemblies spaced circumferentially around an outer circumference. A plurality of slots, spaced circumferentially around the inner circumference, extend from the inner circumference to the support portion. Each latch assembly includes a latch bolt extending through and threadendly engaging a corresponding latch bolt opening in the diaphragm spring. Each latch bolt includes a head and a plurality of ratchet teeth spaced around the periphery of the latch bolt head. A locking spring is positioned to engage the ratchet teeth of the latch bolt head. The latch assembly further includes a latch arm coupled to the latch bolt. The latch arm includes a slot sized to receive a diffuser guide ear.

Abstract: A new approach to scabbling of surfaces of structural materials is disclosed. A layer of mildly energetic explosive composition is applied to the surface to be scabbled. The explosive composition is then detonated, rubbleizing the surface. Explosive compositions used must sustain a detonation front along the surface to which it is applied and conform closely to the surface being scabbled. Suitable explosive compositions exist which are stable under handling, easy to apply, easy to transport, have limited toxicity, and can be reliably detonated using conventional techniques.

Abstract: A jet pump beam bolt locking assembly includes a locking sleeve having a plurality of ratchet teeth extending around the periphery of a base portion, and a lock plate having a beam bolt opening, and an integral beam spring arm having a plurality of ratchet teeth extending from at least a portion of a side of the spring arm. The spring arm ratchet teeth are sized to mesh with the locking sleeve ratchet teeth. The lock plate also includes a lip extending at least partially around the beam bolt opening which captures the locking sleeve. The spring arm is movable between a first position where a lock plate detent is positioned in a spring arm notch which permits engagement of the ratchet teeth, and a second position where the side of the spring arm is in contact with the detent which disengages the ratchet teeth to permit loosening of the beam bolt.

Abstract: A water jet peening apparatus which can carry out an efficient peening work on a large-diameter cylindrical structure by injecting a jet stream which contains air bubbles caused by cavitation at a low angle of incidence is provided. The apparatus is comprised of a nozzle which introduces a high pressure water and injects a water jet stream containing air bubbles caused by cavitation at the cylindrical structure disposed in water, wherein the angle of injection of the jet stream is smaller than 45 degrees relative to a tangent of the cylindrical structure.

Abstract: A method of treating a large scale structural body is provided in which when carrying out and in the large scale structural body such as nuclear reactor pressure vessel and an internal reactor structural body from and to a nuclear reactor building, a used fuel pool and fuels stored inside thereof can be protected even if the large scale structural body drops by some cause. In the method of treating a large scale structural body in which an opening portion is provided at a roof of the nuclear reactor building and the large scale structural body is carried out/in through the opening portion; the carrying out/in of the large scale structural body is performed under a condition that a protective measure for the used fuel pool is provided in a nuclear reactor well.

Abstract: An opening portion 3 is produced by cutting a recirculating piping 72 connected to a recirculating nozzle 2 of a reactor pressure vessel 1. A repairing device is brought into an annulus 10 of the reactor pressure vessel 1 from the opening 3, thereby repairing the annulus 10.

Abstract: The control rod includes an upper absorber section and a lower velocity limiter comprised of a socket, a vane, a transition piece and a set of fins. To adjust the weight of the control rod, lighter and heavier sets of fins, as well as lighter and heavier transition pieces are provided. By suitable selection of the lighter and heavier sets of fins and the lighter and heavier transition pieces, the weight of the velocity limiter can be selectively adjusted in accordance with the weights of differently designed sections to obtain a predetermined control rod weight. Additionally, the heavier transition piece may have material removed therefrom to decrease its weight to provide an infinite adjustment of weight within a predetermined range of weights for the velocity limiter.

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: An adjustment tool is provided, having a probe, a head, an arm and a micrometer attached to the head. With the probe inserted into a spacer cell opening, the micrometer handle is rotated to a predetermined setting to pivot the arm. The opposite end of the arm from its engagement with the micrometer drive head engages and displaces the spring of the spacer cell to adjust its spring force. In one form, the arm is housed within the probe and the micrometer drive head displaces the distal end of the arm outwardly to correspondingly displace the spring outwardly, thereby decreasing the spring force. In another form of the spacer tool, the arm is spaced from the probe and has pivotal contact surfaces to straddle the spring. Movement of the drive head by rotating the micrometer handle to a predetermined setting causes the spring to be displaced inwardly of the spacer cell opening to increase the spacer spring force.

Abstract: An apparatus for reinforcing weakened portions of the top guide assembly in a boiling water reactor. The repair apparatus includes a cruciform lattice segment which reinforces the damaged or weakened region of the top guide beam lattice. This cruciform lattice segment is held in place atop the existing top guide with specially designed straps. The cruciform lattice segment and associated straps are arranged so that a beam segment of the cruciform lattice segment bridges the weakened region in the cracked top guide. Thus, the bridging beam segment transmits loads across the weakened region of the top guide. The straps are designed to avoid interference with removal and installation of the fuel assemblies and the control rod blade which is inserted between the fuel assemblies.

Abstract: A preventive maintenance method and apparatus for a structural member in a reactor pressure vessel according to the present invention reduce a tensile residual stress on a surface of the structural member by impinging a water jet from a nozzle onto a plane surface of a deflector to thereby change direction of flow of the water jet, and impinging the water jet after being deflected onto the surface of the structural member. This method and apparatus are applicable to a narrow space portion, and can improve a residual stress on the surface of the structural member and can also prevent damage such as stress corrosion cracking.