Wrist raster scan methods

Details Wrist raster scan methods Wrist raster scan methods

1998-08-25

2001-04-24

Carone, Michael J. (Department: 3641)

Induced nuclear reactions: processes, systems, and elements

Testing, sensing, measuring, or detecting a fission reactor...

C376S249000, C376S252000, C073S622000, C073S637000, C073S638000, C073S866500

Reexamination Certificate

active

06222897

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to nuclear reactors and, more particularly, to methods and apparatus for inspecting core spray and jet pump riser inlet piping.
BACKGROUND OF THE INVENTION
A reactor pressure vessel of a boiling water reactor typically has numerous piping systems. Such piping systems are utilized, for example to transport water throughout the reactor pressure vessel. For example, core spray piping delivers water to a reactor core.
Over the life of the reactor, the piping is often inspected to verify integrity. For example, the piping welds must be periodically inspected for Inter Granular Stress Corrosion Cracking (IGSCC). Based upon such inspections, the piping may require either repair or replacement.
Problems arise when attempting to inspect small or tight radius elbows on small diameter core spray piping and jet pump riser inlet piping systems, using volumetric ultrasonic techniques. Known pipe inspecting apparatus may not be able to sufficiently cover pipe elbow weld areas for volumetric ultrasonic examinations because of an inability to maintain ultrasonic transducer contact with the surface to be examined.
It would be desirable to provide an easy to use pipe inspection apparatus and methods for inspecting nuclear reactor piping. Preferably, the apparatus and methods would utilize a motion that more readily conforms to the contours of the pipe elbows. It would also be desirable to facilitate maintaining ultrasonic transducers of the inspection apparatus in sufficient contact with the surface of the piping being inspected to allow the ultrasonic transducers to produce accurate scan readings.
SUMMARY OF THE INVENTION
These and other objects may be attained by apparatus for inspecting piping and welds of pipe elbows in a reactor pressure vessel of a boiling water reactor which, in one embodiment, includes a scan head having a pair of spaced apart ultrasonic transducer probes and a motor that moves the scan head axially along the pipe elbow. The scan head allows the transducer probes to remain substantially in contact with the pipe elbow while the scan head traverses the pipe elbow. The ultrasonic transducer probes can detect flaws in the piping and the welds of the pipe elbows and are contoured to conform to the piping.
The scan head also includes a scan platform, a connector, and a pair of transducer arms each having a first end and a second end. Each transducer arm first end is connected to one of the transducer probes. The connector attaches the transducer arms to the scan platform and permits the transducer probes to orbit freely about the connector producing a gimbals type movement. The freedom of movement of the transducer probes allows the probes to remain in contact with the pipe elbow. The scan platform includes an arcuate cutout having a size and shape to accommodate the piping. The connector slides along the arcuate cutout. As the connector slides along the cutout, the transducer probes and the transducer arms are caused to rotate, at least partially, about a circumference of the piping.
The inspecting apparatus further includes a pivot arm having a first end and a second end connected to the scanner platform. A pivot pin is connected to the pivot arm first end. The motor pivots the pivot arm second end about the pivot pin. The pivoting of the pivot arm second end causes the transducer probes to pivot substantially about the pivot pin.
A method of inspecting piping and welds of a pipe elbow using the above described scan apparatus includes positioning the scan head and the ultrasonic transducer probes such that the probes are substantially in contact with the pipe elbow surface. The motor is then used to pivot the transducer probes substantially about the pivot pin which allows the transducer probes to travel axially along the pipe elbow while the probes remain in substantial contact with the pipe elbow surface. The scan head, during this pivoting movement, inspects the piping and the welds in the pipe elbow to detect flaws. The scan apparatus moves with a wrist scan motion to enhance the ability of the probes to remain in contact with the pipe elbow surface during the inspection and to enable ultrasonic transducer signals to better penetrate the piping and welds of the pipe elbow. The piping and the weld material of the pipe elbow are inspected as the transducer probes move substantially perpendicular to the weld.
In operation, the scan head moves axially along the pipe elbow in a first direction from a first axial point to a second axial point. The connector then slides along the cutout, incrementally rotating, in a raster type manner, the probes. The scan head then moves axially along the pipe elbow in a second direction from the second axial point to the first axial point. Again, the connector slides along the cutout, incrementally rotating, in a raster type manner, the probes. Each incremental rotation of the probes moves the probes about a partial circumference of the piping. The axial movement of the probes and the incremental rotation at the ends of the axial stroke are repeated until the probes have inspected the entire surface of the pipe elbow.
A method of positioning ultrasonic transducer probes to examine piping and welds of a pipe elbow begins by locating the above described scan apparatus at the pipe elbow. Since the above described scan apparatus is for use in a reactor pressure vessel of a boiling water reactor, the scan apparatus can be deployed in water to a depth of more than about 60 feet. The scan head is then moved to allow at least a portion of the piping to enter the scan platform cutout. After the transducer probes are positioned substantially in contact with the pipe elbow, the scan head is moved axially along the pipe elbow while the transducer probes are maintained in substantial contact with the pipe elbow. The axial movement of the pipe elbow begins at a first axial point and moves in a first direction to a second axial point. The connector is then moved incrementally along the arcuate cutout which causes the transducer probes and the transducer arms to rotate partially about the circumference of the piping. The scan head is then moved axially along the pipe elbow in a second direction from the second axial point to the first axial point. Again, the connector is moved incrementally along the arcuate cutout which causes the transducer probes and the transducer arms to rotate partially about the circumference of the piping. The axial movement of the probes and the incremental rotation at the ends of the axial stroke are repeated until the probes have investigated the entire surface of the pipe elbow.
The above described scan apparatus allows the ultrasonic transducers to remain in contact with the outer surface of the pipe elbow until the entire inspection has been completed. The wrist scan motion enhances the transducers abilities to contour to the piping surface and enable the transducer signals to better penetrate the surface. The wrist scan motion also enhances the signal dynamics of the transducers enabling the operator to discern between geometric reflections and cracks.


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patent: 4416846 (1983-11-01), Kastl
patent: 4515018 (1985-05-01), Kajiyama
patent: 4672852 (1987-06-01), Gugel et al.
patent: 5118462 (1992-06-01), Dirauf et al.
patent: 11-109081 (1999-04-01), None

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