G-Scan™ Demonstration at Catawba Nuclear Station

G-Scan™ is a long range guided wave inspection tool that uses low frequency ultrasonic waves to interrogate piping integrity. This examination method permits the evaluation of hundreds of feet of fluid filled piping in a single shot. Click on G-Scan™ Technical Specifications for more information.

At Catawba Nuclear Power Station in Clover, South Carolina, Duke Power personnel selected two examination locations based on accessibility for the demonstration. The first location examined was a portion of the 10-inch NPS nuclear service water supply line to the diesel generators; all of this piping lies inside the diesel building. The second location was a 30-inch NPS discharge line in the nuclear service water system pump house; the 30-inch piping was inspected from inside the service water pump house through the wall and out to a buried reducer. Both G-Scan™ locations encompassed areas that had previously been examined using conventional UT methods. Each of the two examinations was completed in less than 30 minutes (including installation of the collar – no paint stripping required). Typically a crew can perform 20 examinations per day. More than 60 feet of the heavily tuberculated 10-inch line was interrogated with a single shot.

Initial interpretation of the data for the 10-inch NPS line indicated that there was significant fouling of the piping. Both locations showed general pitting and corrosion occurring, but no predominant thin areas were identified in the two scans. The G-Scan™ results were generally consistent with prior plant inspection results from sample locations, but also identified locations that were better indicators of worst case system corrosion than the locations that the plant currently inspects. Duke Energy’s conclusion from witnessing Structural Integrity’s demonstration was: “Guided wave examination is a tool that can be used to improve the reliability of our service water piping inspection programs…guided wave examination may be used as a tool to determine where further examination with UT is required to fully characterize pipe degradation.”

Current service water piping inspection programs rely on UT examinations that are performed at discrete sample locations to monitor piping degradation. Sample locations are chosen based on experience and qualitative factors; however, there is no assurance that the sample location chosen is the worst case location for corrosion. The G-Scan™ method can be used to screen long sections of piping, identify the locations with the worst case wall loss, and reveal information on a larger sample size than conventional UT scanning alone. G-Scan™ can reduce the amount of required conventional UT examination locations and increase confidence in lifespan predictions. Large plant savings will be found in reducing plant inspection costs, preventing unexpected failures, and reducing costs associated with unnecessary pipe replacements.

Service Water System Asset Management
For more information, please contact George Licina at (408) 978-8200 or info@structint.com

Nuclear Pipeline Asset Management
For more information, please contact Ken Rach at (630) 728-2094 or info@structint.com.

Other Pipeline Asset Management
For more information, please contact Craig Chaney at (303) 792-0077 or info@structint.com.