Abstract: A method of repairing a crack in a boiling water reactor shroud includes forming a pair of slots in the shroud on opposite sides of the crack in angled relation to one another so that the lateral spacing between the slots increases in a direction parallel to the crack, lowering a wedge clamp with laterally spaced slides into the annular space between the core shroud and the reactor vessel, positioning the slides in the slots, and moving the clamp in the direction of increasing lateral spacing between the slots to an operational position where the clamp prevents unacceptable opening of the crack during reactor operation by providing a structural load path which transmits structural loads across the crack. The slots are preferably configured to mate cooperatively in a manner which prevents the clamp from moving in a radially outward direction relative to the shroud once the clamp has been installed.

Abstract: A method of repairing a crack in a boiling water reactor shroud includes forming a pair of slots in the shroud on opposite sides of the crack in angled relation to one another so that the lateral spacing between the slots increases in a direction parallel to the crack, lowering a wedge clamp with laterally spaced slides into the annular space between the core shroud and the reactor vessel, positioning the slides in the slots, and moving the clamp in the direction of increasing lateral spacing between the slots to an operational position where the clamp prevents unacceptable opening of the crack during reactor operation by providing a structural load path which transmits structural loads across the crack. The slots are preferably configured to mate cooperatively in a manner which prevents the clamp from moving in a radially outward direction relative to the shroud once the clamp has been installed.

Abstract: A method for repairing cracked jet pump riser assemblies in a boiling water reactor utilizes a spacer clamp and a seal collar. The spacer clamp is secured to the riser assembly to limit horizontal displacement of the riser assembly, and the seal collar is secured around the weld joining the riser elbow and the thermal sleeve to limit leakage from the weld over a predetermined range of horizontal displacement defined by the spacer clamp. A method for repairing a circumferential weld connecting an elbow of a jet pump riser assembly with a thermal sleeve involves positioning the weld within a seal collar and securing the seal collar on the jet pump riser assembly so that seals of the seal collar sealingly contact the elbow and the thermal sleeve, respectively, circumferentially on opposite sides of the weld.

Abstract: A method for replacing cracked core spray supply piping in a boiling water reactor vessel includes removal of all or part of the core spray supply piping inside the reactor vessel and replacement of the piping with new piping components configured to couple with one another or any remaining core spray supply piping without being welded. In accordance with one aspect of the invention, a lower elbow of the core spray supply piping is removed and replaced with an elbow assembly configured to mechanically couple with an existing feed-through assembly at the core shroud, for example by use of friction fit, bias members, and/or bolts. A vertical section of the core spray supply piping feeding into the elbow can also be removed and replaced with a new piping section configured to mechanically couple with the replacement lower elbow assembly, for example using pins, clamps and sealing members such as piston rings.

Abstract: A method of repairing a crack in a boiling water reactor shroud with a clamp having pins eccentrically mounted on disks connected by a structural member includes inserting the pins into openings formed in the shroud on opposite sides of the weld and turning the disks to rotate the pins toward the weld such that edges of the holes are engaged by the pins to transmit loads from the shroud to the structural member rather than the weld. A seal member is mounted in compression between a flange at an inboard end of at least one of the pins and an inner surface of the shroud to control leakage through the opening in the shroud.

Abstract: A method of repairing a crack in a boiling water reactor shroud with a clamp having pins eccentrically mounted on disks connected by a structural member includes inserting the pins into openings formed in the shroud on opposite sides of the weld and turning the disks to rotate the pins toward the weld such that edges of the holes are engaged by the pins to transmit loads from the shroud to the structural member rather than the weld. A locking mechanism using set screws can be used to lock the disks in a desired rotational position relative to the clamp.

Abstract: A method of repairing a crack in a boiling water reactor shroud includes forming a pair of slots in the shroud on opposite sides of the crack in angled relation to one another so that the lateral spacing between the slots increases in a direction parallel to the crack, lowering a wedge clamp with laterally spaced slides into the annular space between the core shroud and the reactor vessel, positioning the slides in the slots, and moving the clamp in the direction of increasing lateral spacing between the slots to an operational position where the clamp prevents unacceptable opening of the crack during reactor operation by providing a structural load path which transmits structural loads across the crack. The slots are preferably configured to mate cooperatively in a manner which prevents the clamp from moving in a radially outward direction relative to the shroud once the clamp has been installed.

Abstract: An apparatus for repairing cracked core spray supply piping in a boiling water reactor vessel includes a pair of clamps extending circumferentially around the piping on opposite sides of a crack and a preloading mechanism urging the clamps toward one another to apply and maintain an axially compressive load on the piping tending to close the crack. For vertical sections of core spray supply piping, the clamps are secured at vertically spaced locations with each of the clamps including a first jaw extending circumferentially around a first portion of the piping and including a first opening oriented substantially parallel to a longitudinal axis of the piping and an elongate passage or channel oriented substantially perpendicular to and in communication with the first opening.

Abstract: An apparatus for repairing cracked core spray supply piping in a boiling water reactor vessel includes a pair of clamps extending circumferentially around the piping on opposite sides of a crack and a preloading mechanism urging the clamps toward one another to apply and maintain an axially compressive load on the piping tending to close the crack. For vertical sections of core spray supply piping, the clamps are secured at vertically spaced locations with each of the clamps including a first jaw extending circumferentially around a first portion of the piping and including a first opening oriented substantially parallel to a longitudinal axis of the piping and an elongate passage or channel oriented substantially perpendicular to and in communication with the first opening.

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: 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: 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: 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 of repairing nuclear reactor core shrouds having horizontal cracks in heat affected zones of welds includes applying vertical compressive forces to the shroud in situ to urge opposed surfaces of the cracks toward one another. A plurality of tie rods, angularly spaced about the shroud periphery, is used to selectively apply the longitudinally compressive forces. Preferably, the method utilizes existing hardware secured to the shroud for attaching the tie rods thereto. The tie rods may be used in communication with horizontal and/or vertical spacers inserted between the shroud and the reactor vessel. Horizontal spacers serve to resist horizontal seismic loads and hold the shroud in place in spite of cracking. Vertical spacers resist vertically upward loads resulting from main steam line breaks.

Abstract: A method of repairing nuclear reactor core shrouds having horizontal cracks in heat affected zones of welds includes applying vertical compressive forces to the shroud in situ to urge opposed surfaces of the cracks toward one another. A plurality of tie rods, angularly spaced about the shroud periphery, is used to selectively apply the longitudinally compressive forces. Preferably, the method utilizes existing hardware secured to the shroud for attaching the tie rods thereto. The tie rods may be used in connection with horizontal and/or vertical spacers inserted between the shroud and the reactor vessel. Horizontal spacers serve to resist horizontal seismic loads and hold the shroud in place in spite of cracking. Vertical spacers resist vertically upward loads resulting from main steam line breaks.

Abstract: A method of repairing a tubular nozzle made of Inconel 600 material and extending through a bore in an external wall of a pressure vessel to provide communication with the interior of the vessel from externally thereof includes mechanically rolling the inside diameter of a portion of the nozzle disposed within the external wall with a roll pressure in the range of 50,000 to 150,000 psi to form a circumferential rolled section in the nozzle having a wall thickness 3% to 12% less than the wall thickness of non-rolled sections of the nozzle, an outside diameter less than 1% greater than the outside diameter of the non-rolled sections and transition segments with a radius of curvature in the range of 1/2 inch to 2 inches joining the rolled section to the non-rolled sections.

Abstract: A steam generator chemical solvent mixing system and method is provided. The chemical solvent mixing system includes a pump, having a discharge port fluidly connected to a discharge line and a suction port fluidly connected to a suction line. An upper level injector, including an injector nozzle extends through one upper access opening in the outer casing of a steam generator and extends into the annulus of the generator between the tube bundle shroud and the outer casing, the upper level injector being fluidly connected to the discharge port of the pump. A lower access eductor is provided, including an eductor nozzle extending through one lower access opening of the outer casing and adapted to discharge solvent through one passageway in the tube bundle shroud and into the tube bundle of the generator, the lower access eductor being fluidly connected to the discharge port of the pump.

Abstract: Built-up deposits on the top surface of a tubesheet and on adjacent tube sections in a tube bundle heat exchanger are removed by inducing vigorous turbulent flow of cleaning liquid radially along the surface of the tubesheet by repetitively and periodically injecting gas pulses into the liquid to form an expanding and retracting gas bubble proximate the plate center. The gas pulse rise time is smoothed by controlling the actuation time of a discharge valve and by a surge volume downstream of the valve to thereby avoid harmful pressure shock waves in the heat exchanger. The cleaning liquid is recirculated through an external filter loop to remove suspended foreign materials dislodged by the turbulent flow.

Abstract: A non-corrosive, non chemical cleaning process for tube bundle heat exchangers develops and physically transmits kinetic energy in the form of a vigorous, high volume "water slap" to dislodge internally accumulated contaminants. A plurality of injectors periodically inject discrete quantities of pressurized inert nitrogen into the heat exchanger downcomer annulus, near the steam generator bottom, and in response to the expanding gas bubble the water column established in the tube bundle is accelerated upwardly. A rapid displacement of a body of water causes the surface of the water to slap debris from components in its path. The water column level is established slightly below the bottom of a tube support structure, and the rapid rise of the water surface impacts the bottom of the structure and is forced through the water flow passageways where the fluid flow acceleration pressures dislodge the accumulated debris.