Technical Letter Report, An Evaluation of Ultrasonic Phased Array Testing for Reactor Piping System Components Containing Dissimilar Metal Welds, JCN N6398, Task 2A

Abstract

National Laboratory to assess the effectiveness and reliability of advanced nondestructive examination (NDE) methods for the inspection of light-water reactor components. The scope of this research encompasses primary system pressure boundary materials including dissimilar metal welds (DMWs), cast austenitic stainless steels (CASS), piping with corrosion-resistant cladding, weld overlays, inlays and onlays, and far-side examinations of austenitic piping welds. A primary objective of this work is to evaluate various NDE methods to assess their ability to detect, localize, and size cracks in steel components that challenge standard and/or conventional inspection methodologies. This interim technical letter report (TLR) provides a summary of a technical evaluation aimed at assessing the capabilities of phased-array (PA) ultrasonic testing (UT) methods as applied to the inspection of small-bore DMW components that exist in the reactor coolant systems (RCS) of pressurized water reactors (PWRs). Operating experience and events such as the circumferential cracking in the reactor vessel nozzle-to-RCS hot leg pipe at V.C. Summer nuclear power station, identified in 2000, show that in PWRs where primary coolant water (or steam) are present under normal operation, Alloy 82/182 materials are susceptible to pressurized water stress corrosion cracking (PWSCC) (NRC 2008b(NRC , 2009). The extent and number of occurrences of DMW cracking in nuclear power plants (domestically and internationally) indicate the necessity for reliable and effective inspection techniques. The work described herein was performed to provide insights for evaluating the utility of advanced NDE approaches for the inspection of DMW components such as a pressurizer (PZR) surge nozzle DMW, a shutdown cooling pipe DMW, and a ferritic (low-alloy carbon steel)-to-CASS pipe DMW configuration.In this study, a set of flaws, including both thermal fatigue cracks and electrical discharge machining (EDM) notches that were hot isostatically pressed (HIP'ed) were inserted into five DMW mock-up specimens. The DMW specimens used in this study were either salvaged from a cancelled plant that had never been in an operational state, or were fabricated from new and/or vintage materials. PA-UT flaw responses from these cracks were used to evaluate detection and characterization performance. The PA-UT examination approach used on the DMW component mock-ups focused on acquiring data as a function of inspection frequency (2.0 MHz, 1.5 MHz, and 1.0 MHz), inspection angle (30° to 70° in 1° increments), and by employing both raster and line-scan data acquisition. Data were acquired from both sides of the welds; however, the focus in this document is to evaluate inspection performance by assessing the data taken from the austenitic side of the DMW configuration, as this is the side where an inspector typically has access in the field. The data analyses conducted here provide quantitative information regarding detection and sizing performance against the true state. Additional metric...

Ultrasonic Evaluation of Two Dissimilar Metal Weld Overlay Specimens

“…Phased-array data were acquired on Specimen 9C-034 prior to the application of the WOL as part of an earlier study (Diaz et al 2009a) on evaluating DMW specimens. These Pre-WOL data were acquired from the CASS pipe side of the weld with the 1.5-and 2.0-MHz phased-array probes in both the line and raster styles of scanning.…”