An Ultrasonic Phased Array Evaluation of Cast Austenitic Stainless Steel Pressurizer Surge Line Piping Welds

Diaz, Aaron A.; Cinson, Anthony D.; Crawford, Susan L.; Moran, Traci L.; Anderson, Michael T.

doi:10.1115/pvp2010-25799

Cited by 5 publications

(9 citation statements)

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“…To date using these frequencies, inspections can reliably detect flaws in the 25%-30% through-wall range. (Diaz et al 2011) provides information on crack detection with UT in thinner-walled cast stainless steel. The information in these NUREGs should be helpful to industry in improving the reliability of inspections and to NRR in evaluating relief requests and inspection-related issues involving cast stainless steel.…”

Section: Inspection Limitationsmentioning

confidence: 99%

Assessment of the Mechanical Stress Improvement Process for Mitigating Primary Water Stress Corrosion Cracking in Nickel Alloy Butt Welds in Piping Systems Approved for Leak-Before-Break

Sullivan¹,

Anderson²

2013

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Executive SummaryIn recent years, operating experience has shown that Alloy 82/182/600 materials used in reactor coolant system (RCS) pressure boundaries of pressurized water reactors (PWRs) are susceptible to primary water stress corrosion cracking (PWSCC). Cracking can initiate at the inside surface of these materials, in part, because of tensile residual stresses introduced by welding. These materials are present in piping systems that were approved by the U.S. Nuclear Regulatory Commission (NRC) for leakbefore-break (LBB) before PWSCC was found in RCS dissimilar metal butt welds. The identification of PWSCC led to concerns regarding the potential effect of this degradation on existing LBB analyses.In response to these concerns, the NRC Office of Nuclear Regulatory Research initiated a program entitled, "PWSCC in Leak-Before-Break Systems," and a follow-on program entitled, "Degradation in Extremely Low Probability of Rupture (xLPR) Systems." Under these programs, Pacific Northwest National Laboratory (PNNL) is assessing the various strategies being used by industry to manage potential or existing PWSCC in susceptible welds in piping systems approved for LBB.The commercial nuclear power industry has implemented strategies to manage potential or existing PWSCC at Alloy 82/182 dissimilar metal welds (DMW) in PWRs. One general strategy consists of management by a combination of mitigation plus inspection, where several mitigation techniques have been used by industry. The other general strategy is to manage potential PWSCC by inspection alone.At the request of the NRC, the American Society of Mechanical Engineers (ASME) took actions to develop improvements to the existing Code requirements to address the potential for PWSCC in Class 1 PWR piping butt welds fabricated with Alloy 82/182 weld materials. The ASME developed Code Case N-770, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated with UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities, Section XI, Division 1." It was realized that the Code Case needed to be revised to address specific examinations such as welds with a design life of less than 10 years and post-weld preservice surface examinations. In general, the revised Code Case (N-770-1) has requirements for inspection of unmitigated as well as mitigated Alloy 82/182 RCS butt welds. As such, specific inspection requirements for welds mitigated by the Mechanical Stress Improvement Process (MSIP®), (a) the subject of this technical letter report (TLR), are contained in the Code Case. The NRC incorporated ASME Code Case N-770-1 by reference into §50.55a (76 FR 36232, p. 36278) in June 2011.This TLR provides an assessment of MSIP as a mitigation strategy and includes an assessment of the MSIP-related inspection requirements of Code Case N-770-1, as conditioned in §50.55a.Depending upon the weld geometry, fabrication practices, and the presence of a nearby safe end-topipe weld, Al...

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Section: Inspection Limitationsmentioning

confidence: 99%

Assessment of the Mechanical Stress Improvement Process for Mitigating Primary Water Stress Corrosion Cracking in Nickel Alloy Butt Welds in Piping Systems Approved for Leak-Before-Break

Sullivan¹,

Anderson²

2013

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“…The three specimens were stamped with identification numbers. Specimen 7C-059 was the initial PZR surge-line specimen first acquired by PNNL and reported by Diaz et al (2008). Figure 3.1 shows a side-and end-view of this specimen.…”

Section: Rules For Inservice Inspection (Isi) Of Nuclear Power Plant mentioning

confidence: 99%

“…This letter report provided a status of technical activities that included initial ultrasonic experiments on machined reflectors to ascertain the optimal center frequency for sound propagation and crack detection in these materials. Later in 2008, PNNL submitted to the NRC PNNL-17698, Assessment of Ultrasonic Phased Array Testing for Cast Austenitic Stainless Steel Pressurizer Surge Line Piping Welds and Thick Section Primary System Cast Piping Welds (Diaz et al 2008), summarizing on-going assessments of lower-frequency PA inspection methods on both small-and large-bore CASS piping, and providing insights into the application of a PA delta technique for detection of tip-diffracted energy in this piping. Since that time, probe design improvements, acquisition of additional PZR surge-line specimens, greater knowledge of the microstructures, and technological developments to the PA scanning/analysis system required the acquisition of new data.…”

Section: Introduction and Objectivesmentioning

confidence: 99%

Technical Letter Report Assessment of Ultrasonic Phased Array Inspection Method for Welds in Cast Austenitic Stainless Steel Pressurizer Surge Line Piping JCN N6398, Task 1B

Diaz¹,

Cinson²,

Crawford³

et al. 2009

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Research is being conducted for the U.S. Nuclear Regulatory Commission (NRC) at the Pacific Northwest National Laboratory (PNNL) 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 cast austenitic stainless steels (CASS); dissimilar metal welds; 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 coarsegrained steel components. In this effort, PNNL supports cooperation with Commissariat à l'Energie Atomique (CEA) to assess reliable inspection of CASS materials. The NRC Project Manager has established a cooperative effort with the Institut de Radioprotection et de Surete Nucleaire (IRSN). CEA, under funding from IRSN, are supporting collaborative efforts with the NRC and PNNL. Regarding its work on the NDE of materials, CEA is providing its modeling software (CIVA) in exchange for PNNL offering expertise and data related to phased-array detection and sizing, acoustic attenuation, and back scattering on CASS materials. This collaboration benefits the NRC because CEA performs research and development on CASS for Électricité de France (EdF).This technical letter report 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 welds in CASS pressurizer (PZR) surge line nuclear reactor piping. A set of thermal fatigue cracks (TFCs) was implanted into three CASS PZR surge-line specimens (pipe-to-elbow welds) that were fabricated using vintage CASS materials formed in the 1970s, and flaw responses from these cracks were used to evaluate detection and sizing performance of the PA-UT methods applied. This effort was comprised of multiple elements that included use of microstructural knowledge (dimensional analysis, grain orientation, and grain type) as well as sound field modeling to more effectively modify inspection parameters and enhance the inspection outcomes. Advanced probe design and sound field simulations were employed to enhance detection and characterization of circumferentially oriented flaws, and an assessment of lateral (circumferential) flaw localization capability and performance was also conducted. An evaluation of flaw detection, length sizing, depth sizing, and signal-to-noise ratio was performed for all flaws in the subject specimens, as a function of various inspection parameters, and finally, measurements were made to quantify and assess the baseline CASS material noise and its potential impact on flaw detection.Previous work has been focused on heavy-walled primary loop piping components with outer diameters (OD) ranging from 71.12 to 91.44 cm (28 to 36 in.). However, a variety of thinner cas...

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“…Over the past many years, PNNL has focused much of its laboratory and field-based research toward addressing the prevalent inspection issues associated with detection and characterization of flaws through coarsegrained microstructures in CASS components. As PNNL has documented recent technical progress with the inspection of smaller-bore CASS components (Diaz et al 2008), specific (and technically related) inspection challenges associated with DMWs have emerged. In some DMW configurations where CASS piping is used, inspection from the far-side (through the CASS parent material, weld, and Inconel buttering) is required because, for example, component configuration precludes adequate placement of probes on the other side of the weld.…”

Section: Background and Objectivesmentioning

confidence: 99%

“…Since 1977, PNNL has conducted advanced NDE research under the sponsorship and guidance of the NRC to evaluate state-of-the-art technical approaches for inspecting nuclear reactor components that pose significant challenges to conventionally employed inspection methods used in the nuclear industry (Taylor 1984;Diaz et al 1998;Anderson et al 2007;Diaz et al 2008). This work recently has focused on assessing the viability and effectiveness of phased-array ultrasonic NDE methods applied from the outside pipe surface where the material composition is detrimental to performing effective inspection and component configurations affect probe placement.…”

Section: Background and Objectivesmentioning

confidence: 99%

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

Diaz¹,

Cinson²,

Crawford³

et al. 2009

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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...

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An Ultrasonic Phased Array Evaluation of Cast Austenitic Stainless Steel Pressurizer Surge Line Piping Welds

Cited by 5 publications

References 0 publications

Assessment of the Mechanical Stress Improvement Process for Mitigating Primary Water Stress Corrosion Cracking in Nickel Alloy Butt Welds in Piping Systems Approved for Leak-Before-Break

Assessment of the Mechanical Stress Improvement Process for Mitigating Primary Water Stress Corrosion Cracking in Nickel Alloy Butt Welds in Piping Systems Approved for Leak-Before-Break

Technical Letter Report Assessment of Ultrasonic Phased Array Inspection Method for Welds in Cast Austenitic Stainless Steel Pressurizer Surge Line Piping JCN N6398, Task 1B

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

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