United States Nuclear Regulatory Commission - Protecting People and the Environment

Applying Ultrasonic Testing in Lieu of Radiography for Volumetric Examination of Carbon Steel Piping (NUREG/CR-7204, PNNL-24232)

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Publication Information

Manuscript Completed: May 2015
Date Published: September 2015

Prepared by:
T. L. Moran, M. Prowant, C. A. Nove*, A. F. Pardini,
S. L. Crawford, A. D. Cinson, and M. T. Anderson

Pacific Northwest National Laboratory
P.O. Box 999
Richland, WA 99352

*U.S. Nuclear Regulatory Commission

C. A. Nove, NRC Project Manager

NRC Job Code V6097

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

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Abstract

Confirmatory research is being conducted for the U.S. Nuclear Regulatory Commission at the Pacific Northwest National Laboratory to assess the effectiveness and reliability of advanced nondestructive examination methods as they are applied to pressure boundary components and other materials installed in light-water reactors. The work reported here provides an initial technical evaluation of the capabilities of phased-array ultrasonic testing to supplant traditional radiographic testing for detection and characterization of welding fabrication flaws in carbon steel welds. The work was performed on a limited set of piping girth welds and welded plates containing varied types and sizes of volumetric and planar fabrication flaws. Phased-array ultrasonic data were acquired using transmit-receive shear waves at 4.0 and 5.0 MHz, and compared to consensus evaluations and computed radiography in correlating detection and flaw characterization capabilities. The results show that, for carbon steel, phased-array ultrasonic testing is capable of detecting all but very small volumetric flaws, and is much more capable of detecting planar flaws than standard radiographic techniques. The study also shows that characterization of flaws using ultrasonic testing (i.e., determining whether a flaw is volumetric or planar in nature) can be highly subjective based on operator experience; thus, radiographic imaging may have an advantage over ultrasonic imaging in this regard. Finally, several technical knowledge gaps were discovered as a result of this work, including the lack of appropriate performance demonstration standards and robust acceptance criteria for fabrication weld inspection (i.e., fitness for service versus workmanship standards).

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