Mpr Associates, Inc.

Westinghouse Electric Corporation

Other

Arkansas Power and Light Company

Sterling J Weems

William E Sylvester

Noman Cole

Harold W McCurdy, Jr

William R Schmidt

Albert C Buford, Iii

Donal W Moore

John B Mason

H William McCurdy

Thomas E Greene

Hans D Giesecke

Harold William McCurdy, Jr

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. The clamp can also be provided with locking members such as screws which extend from the clamp in a direction opposite the direction of increasing lateral slot spacing to hold the clamp in place by contacting walls of the slots.

Repaired shroud assembly for boiling water reactor

Wedge clamp for repairing boiling water reactor shroud

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. A spacer clamp for limiting horizontal displacement between a shroud and a jet pump riser assembly includes inboard and outboard clamp members for seating against the pipe, with the inboard clamp member establishing a gap with the shroud corresponding to a predetermined amount of horizontal displacement allowed between the shroud and the pipe. A seal collar for limiting leakage from a crack in piping of a boiling water reactor includes a pair of hinged jaw members movable between an open position for receiving a pipe therebetween and a closed position encircling the pipe at the location of the crack, and pairs of seals disposed along inner surfaces of the jaw members, respectively, forced into sealing, circumferential contact with the pipe on opposite sides of the crack to limit leakage from the crack.

Methods and apparatus for repairing a cracked jet pump riser in a boiling water reactor utilizing a spacer camp

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. In accordance with another aspect of the invention, the vertical piping section is removed along with an upper elbow, horizontal core spray supply arms and the flow divider or T-box and replaced with a new T-box assembly and piping. The T-box assembly can be connected to the piping using any of the disclosed joints and can carry replacement thermal sleeves which fully replace or supplement existing thermal sleeves. Various biasing and detent mechanisms are disclosed for mechanically coupling the new T-box assembly with the existing safe end assembly.

Method for replacing cracked core spray supply piping in a boiling water reactor

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.

Method for repairing vertical welds in a boiling water reactor shroud using a clamp with eccentric pins sealed against an interior of the shroud

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.

Method for repairing vertical welds in a boiling water reactor shroud using a clamp with eccentric pins

Method for repairing vertical welds in a boiling water reactor shroud

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. A second jaw extends circumferentially around a second portion of the pipe in horizontally opposed relation to the first jaw and includes an elongate extension slidably received in the elongate channel and defining a second opening partially aligned with the first opening, with a wedge being movably disposed in the aligned openings to cause the second jaw to move relative to the first jaw in a direction substantially perpendicular to the longitudinal axis of the piping in response to straight, vertical operations. For horizontal sections of core spray supply piping, the clamps are secured at horizontally spaced locations with each of the clamps having a pair of jaws extending circumferentially around the piping in opposed relation and a horizontal preloading mechanism extending between the jaws in tension, the horizontal preloading mechanism being similar to the clamping mechanism used for vertical sections to facilitate installation using straight, vertical operations.

Apparatus for repairing cracked core spray supply piping in a boiling

Method and apparatus for repairing cracked core spray supply piping in a

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. Existing safe end assemblies welded to core spray supply piping in the reactor vessel are removed and replaced with new safe end assemblies carrying components which mechanically couple with core spray supply piping carried by the replacement core shroud.

Replacement core shroud assembly for a boiling water reactor

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. In a preferred embodiment, the seismic support defines a bearing surface in spaced relation with an interior surface of the reactor vessel to define a clearance gap that minimizes the frequency and magnitude of impacts between the core shroud and the reactor vessel.

Seismic support with clearance gap and yieldable member

Method of replacing a boiling water reactor core shroud

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. The upper portion of each brace can be clamped to a tubular core sparger disposed within the upper cylindrical section and can be held in compression between the shroud flange and the upper core grid structure, or the horizontal plate directly, with a jacking bolt threadedly engaging the brace and having a lower end bearing against the upper core grid structure or the horizontal plate.

Method and apparatus for repairing boiling water reactor shrouds

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.

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.

Growing community of inventors

Chevy Chase, MD, United States of America

Sterling J Weems