General Electric Company

David L Richardson

Jack P Clark

Richard W Perry

Thurman D Smith

Peter M Patterson

James H Terhune

Balasubramanian S Kowdley

James C Tung

Gerald A Deaver

David C Berg

Jack Toshio Matsumoto

Frank Ortega

Edward R Dykes

Yehuda Krampfner

Gunnar V Vatvedt

Michael Edward Mosseau

Mary M Lemanowicz

John G De Briere

Willem Vanderputten

Scott R Stanton

Brian Charles Duckering

A method and an apparatus for ultrasonically inspecting the welds which attach the differential pressure and liquid poison nozzles to the bottom head of the reactor pressure vessel in a boiling water reactor. The scanning apparatus is seated on the upper taper of the nozzle outer tube and incorporates a stationary frame having a cutaway section which allows installation from the side. The apparatus has vertical and circumferential positioning mechanisms which are operated remotely to scan an ultrasonic transducer package over the circumferential welds and heat-affected zones thereof. The rotating frame has a transducer carriage mounted thereon which is vertically displaceable relative to the rotating frame. The vertical and angular motion motors can be controlled together to provide the desired path for the ultrasonic transducer around the stub tube. The tool also includes a vessel contour follower which follows the contour of the inclined surfaces of the reactor pressure vessel bottom head. The vessel contour follower is linked to the ultrasonic transducer to ensure that the transducer follows the contour of the weld, in position and angle.

Method and apparatus for remote ultrasonic inspection of nozzles in

An integrated apparatus for inspecting the arms of jet pump beams using eddy current technology, while also scanning the borehole region using ultrasound technology. In order to inspect the jet pump beam arms, a special scanner is required to properly move an eddy current coil in two dimensions over the complex machined surface on top of the arms. The scanner has two axes of motion and can perform a raster scan in either direction. The inspection payload, an eddy current probe, moves the length of the scanning axis and then the payload is indexed (i.e., moved a small distance) along the indexing axis. The payload is then moved smoothly back along the length of the scanning axis. Data is collected only during motion along the scanning axis. The scanner has a unique curved track design for maintaining the orientation of the eddy current probe perpendicular to the inspection surface. It allows inspecting the top flat surface and the curved edges of the jet pump beams. The eddy current probe is mounted on a movable carriage which rolls along the curved track via two wheels which move along two different curves having the same radius, but different arc lengths.

Inspection tool for detecting cracks in jet pump beams of boiling water

A method and an apparatus for in situ ultrasonic inspection of the core spray T-box to thermal sleeve attachment weld and the core spray T-box to cover plate attachment weld in BWRs. The apparatus incorporates a stationary clamping mechanism and sliding and rotational mechanisms which are operated remotely to scan the transducer over the T-box welds and heat-affected zones thereof. The T-box weld inspection tool comprises the following assemblies: clamping jaws for clamping the tool onto the T-box arms in response to activation of a pair of pneumatic cylinders; a side slide stage having a transducer carriage which is slidable in parallel with the centerline axis of the thermal sleeve in response to activation of a first drive motor; a radial face stage having a transducer carriage which is slidable in a direction perpendicular to the centerline axis of the thermal sleeve in response to activation of a second drive motor; and a rotation stage which rotatably supports both the side slide stage and the radial face stage for rotation about the centerline axis of the thermal sleeve in response to activation of third and fourth drive motors, respectively. The transducers carried on the radial face stage are used to interrogate the T-box to cover plate attachment weld; the transducers carried on the side slide stage are used to interrogate both the T-box to cover plate and the T-box to thermal sleeve attachment welds.

Method and apparatus for remote ultrasonic inspection of core spray

An ultrasonic method of inspecting repaired stub tubes in a boiling water reactor. The top and bottom ends of each stub tube are respectively welded to the corresponding control rod drive housing and to the bottom head of the reactor pressure vessel. Under certain conditions, a crack can form in the heat-affected zone of the stub tube adjacent to the upper weld, necessitating repair by installing a mechanical seal. A probe inserted in the control rod drive housing has transducers which transmit pulsed ultrasonic energy toward a machined surface-air gap interface disposed to reflect the pulse trains generally axially through the stub tube. The radial and azimuthal dimensions of a radial crack in the stub tube are determined in dependence on which pulsed trains are reflected back to the probe by the crack via the interface.

Method of inspecting repaired stub tubes in boiling water nuclear

An automated system for examining incore housing welds in a nuclear reactor from above is disclosed. The probe uses both ultrasonic and eddy current non-destructive inspection coils to examine the weld for indications, or flaws. It is inserted into the incore housing tube from above because of the high radiation exposure workers experienced using the prior method of inserting a probe into the incore housing from below. This is conveniently done when the incore flux monitors are removed during standard maintenance, and is performed from the refueling bridge.

Incore housing examination system

An improved apparatus and method for ultrasonic inspection of materials through barriers such as gaps in manufactured parts is disclosed. The improvement herein is directed to enabling such ultrasonic testing to bridge ambient gaps such as intentionally formed gaps in composite structures having a first structure for originally receiving and transmitting sound separated by the gap from another structure to be inspected. Preferably, the gap is flooded with a gas having a predictable and optimum speed of sound relative to the material of the first and second structures. Sound is propagated to the first structure in a wave packet that is transmitted through the couplant fluid. The sound is generated in a wave packet having a spatial width at least twice the dimension of the gap to be bridged. The wave packet has a contained frequency having a wavelength (relative to the speed of sound of the gas flooding the gap) to create a constructively interfering standing wave node within the gap. The sound propagated to the gas-filled gap has a wavelength which is a half-integer with respect to the gap dimension. Sound passes through the first structure, creates a standing wave node in the gas-filled gap, passes into and acoustically interrogates the second structure for flaws and reflects. Reflected ultrasoound from the interrogated second structure again bridges the gap as a constructively interfering standing wave, passing through the primary structure and then through the couplant fluid to a transducer for receipt and analysis of the received ultrasound.

Method of ultrasonic inspection of materials through opaque barriers

An apparatus and process for the remote inspection for stress corrosion cracking of welded shut boiling water reactor shroud access cover plates is disclosed. The apparatus consists of a streamline housing having a top side with lugs for the attachment of lowering lines on either end of the housing. Medially of the streamline housing and projecting downwardly from the bottom of the streamline housing, there is provided a central rotating pedestal with a rubber base. The rotating pedestal and rubber base enable the entire housing to rest on and rotate relative to the pedestal and rubber base. A first motor interior of the housing rotates the housing at a bevel gear rigidly mounted to the central pedestal. A second motor rotates a threaded shaft driving a ball screw with an attached mount for an ultrasound transducer. The mount and transducer responsive to rotation of the ball screw traverse along the elongate dimension of the housing over an opening through the bottom of the housing. A focused ultrasound transducer passes above the metal to be inspected. This ultrasound transducer focuses the sound through the water at an oblique angle to and from the metal of the hatch cover plate for an ultrasonic examination for stress corrosion cracking.

Apparatus for ultrasonic examination of BWR shroud access cover plate

In operation, the device is lowered with paired lines attached to both housing lugs but suspended under tension only from one line to one lug so that the streamline housing is vertically disposed. With the housing vertically disposed during lowering, obstacles can be avoided such as the guide rod for the steam separator and dryer as well as the feedwater and core spray spargers. When lowered to the vicinity of the ledge and cover plate to be inspected, the slack line is fished around any obstacle and thereafter placed under tension. The streamline housing is then lowered using both lines in a horizontal position so as to expose downwardly the pedestal and rubber foot. Lowering is completed with remote camera assistance. Sample sweeps with the ultrasound transducer of spaced apart sections of the cover plate weld are used for precise centering of the pedestal and rubber base with respect to the center of the cover plate. Repeatedly logging a longitudinal excursion of the ultrasound detector with indexed rotation of the housing permits scanning entirely around the weld of the cover plate. This enables remote ultrasound survey of the weld of the cover plate for stress corrosion cracking.

Ultrasonic examination of BWR shroud access cover plate retaining welds

In a boiling water reactor, an apparatus and process for ultrasound inspection of the top guide is disclosed. The top guide constitutes a lattice of stainless steel bars overlying the core plate and being assembled at confronting grooves with the lattice mounted at the side edges to the reactor pressure vessel. This lattice braces the upper ends of the vertically supported fuel assemblies in their requisite orientation and spaced apart relation to enable among other things the required spatial interval to be maintained for control rod moderation of the reaction. Because of the proximity of the top guide to the fuel assemblies, the individual bars making up the lattice need to be checked for cracking, especially that cracking produced by irradiation assisted stress crack corrosion. With a defined cell in the lattice emptied of its contained and adjoining fuel assemblies, there is disclosed an ultrasound test for cracking. A sound transducer on a first special frame sweeps horizontally across the top of a bar interrogating the bar with vertical ultrasound waves for detecting horizontal cracks. Similarly, a sound transducer on a second special frame sweeps vertically across the side of a bar interrogating the bar with angularly incident horizontal ultrasound waves for detecting vertical cracks. Nondestructive testing of the lattice assembly occurs without required disassembly.

Ultrasonic examination of reactor pressure vessel top guide

An apparatus for the remote examination of peripheral shroud hold down bolts on steam separators used in boiling water reactors is disclosed. The testing apparatus is used while the steam separator is in a holding pool. The testing apparatus includes a depending pole having attached at the bottom thereof an aluminum shoe. The shoe has a flat, upwardly exposed bottom and opens to one side at gathering surfaces to receive the lower ends of the shroud bolts. The upwardly exposed bottom of the shoe defines an aperture through which an upwardly exposed piezoelectric device is exposed for direct contact with the bottom of the bolt. An overlying clamp member is provided to clamp the lug onto the bottom of the shoe for testing. The clamp member defines a receiving slot to receive the shaft of the bolt immediately overlying the rectangular lug. The clamp member slides over the shaft at the slot into contact with the top of the lug. The clamp member clamps the lug end of the bolt securely onto the upwardly exposed piezoelectric device on the upwardly exposed bottom of the shoe. A piezoelectric ultrasonic test is then run from the bottom and radioactive portion of the bolt to and towards the top of the bolt. Testing for longitudinal sound waves, refracted sound waves and shear sound waves for inter granular stress corrosion cracking can occur despite the radioactive and remote under water location of the bolts.

Apparatus for the ultrasonic examination of shroud hold down bolts

Apparatus for remotely controlled examination of the control rod drive penetration stub tubes in the wall of a nuclear reactor pressure vessel including a rotatable carriage on which is mounted a reciprocable shaft to which is attached an inspection instrument for scanning the stub tubes.

Stub tube inspection device

An ultrasonic transducer apparatus and method for examining nuclear reactor jet pump beams for cracking. Examination is conducted in situ. An operator lowers a carriage portion of the apparatus into the reactor vessel with a pole. Ultrasonic signals are transmitted through suitable wiring from an external source to the transducer apparatus, which may employ a pitch-catch or pulse-echo mode of ultrasonic examination to test the beams. The carriage holds oppositely disposed pairs of ultrasonic transducers and positions them suitably near the beam to be examined in a proper orientation thereto. The mode of examination is selected by a switching mechanism. The apparatus includes a signal generator, receiver, and visual display.

Growing community of inventors

Los Gatos, CA, United States of America

David L Richardson