2012 TECHNICAL REPORT

Electric Power Research Institute 3420 Hillview Avenue, Palo Alto, California 94304-1338 • PO Box 10412, Palo Alto, California 94303-0813 USA

800.313.3774 • 650.855.2121 • askepri@epri.com • www.epri.com

Nondestructive Evaluation: Indication Characterization, Evaluation, and Disposition Guideline

EPRI Project Manager H. Stephens

3420 Hillview Avenue Palo Alto, CA 94304-1338 USA PO Box 10412 Palo Alto, CA 94303-0813 USA 800.313.3774 650.855.2121

askepri@epri.com 1025225

www.epri.com Final Report, October 2012

Nondestructive Evaluation: Indication Characterization, Evaluation, and Disposition

Guideline

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Nondestructive Evaluation: Indication Characterization, Evaluation, and

Disposition Guideline. EPRI, Palo Alto, CA: 2012.

1025225.

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Acknowledgments The following organization prepared this report:

Electric Power Research Institute (EPRI) 1300 West W.T. Harris Blvd. Charlotte, NC 28262

Principal Investigator H. Stephens

This report describes research sponsored by EPRI.

EPRI thanks Philip Ashwin, Michael Blanchard, Leif Esp, Bret Flesner, Douglas Kull, Carl Latiolais, Greg Selby, and Ronald Swain for their contributions to this report.

Contributors to this research include the following:

M. Brooks Detroit Edison Company

R. Linden PPL Susquehanna, LLC

A. Reed Constellation Energy Group

L. Spiess South Texas Project Nuclear Operating Company

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Abstract Operating experience of in-service inspections (ISIs) of nuclear power plants includes cases in which human error or inadequate implementation of examination plans resulted in issues with the application of qualified nondestructive evaluation (NDE) procedures. These issues can result in degraded NDE performance. The operating experience for the basis of the initial report centered principally on ultrasonic testing (UT) examination of dissimilar metal welds (DMWs) in reactor piping systems. The more recent operational experience continues to be based on improper interpretation of UT welds in reactor piping systems, although one instance centered on not detecting the discontinuities, rather than improper interpretation. This report is being expanded to address NDE methods in addition to ultrasonics. These methods are liquid penetrant, magnetic particle, and radiographic examination.

This report provides guidance for nuclear power plant owners in planning and executing NDE so that the process for identification, characterization, evaluation, and disposition of detected indications by various NDE methods is addressed in a systematic manner. Based on a review of nuclear power plant approaches to NDE information processing, there are two different philosophical approaches typically used: bottom-up and top-down. Both approaches have advantages for the initial detection of indications. After an indication is detected and confirmed to be a true indication, the accurate determination of whether it is a relevant or a nonrelevant indication can require significant effort and time. A comprehensive understanding by all involved of the systematic process required to make an accurate determination is essential. This understanding of the process and the time necessary to accomplish it will minimize the occurrence of significant human errors while maximizing the probability of a smoothly executed outage with completion of the planned scope. Because the principal purpose of ISI is the detection of service-related flaws, the development of a comprehensive outage contingency plan is essential to minimizing the impact when relevant indications are detected. This report does not address any recommendations in accordance with the Nuclear Energy Institute 03-08, Revision 1, Guideline for the Management of Materials Issues.

Keywords Indication evaluation Nondestructive evaluation (NDE) Liquid penetrant examination Radiographic examination Magnetic particle examination Ultrasonic testing (UT)

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Table of Contents

Section 1:  Introduction ............................................. 1-1 Background ..................................................................... 1-1 Glossary ......................................................................... 1-6 

Section 2:  General Considerations for Evaluation of NDE Indications ................................... 2-1 

Interpretation, Characterization, and Evaluation .................. 2-1 

Section 3:  Process for Interpretation of Manual Ultrasonic Indications ............................... 3-1 

UT Oversight ................................................................. 3-15 NDE Data from Prior Examinations ................................... 3-15 Supplemental NDE ......................................................... 3-17 Service History ............................................................... 3-17 Contingency Plans .......................................................... 3-23 

Section 4:  General Consideration for Interpretation and Evaluation of Radiographic, Magnetic Particle, and Liquid Penetrant Indications ..................... 4-1 

Section 5:  Process for Interpretation of Radiographic Indications ......................... 5-1 

Introduction ..................................................................... 5-1 Background ..................................................................... 5-1 Analog Images ................................................................ 5-2 

Image Quality ............................................................ 5-2 Radiographic Density ....................................................... 5-3 

Density Limitations ...................................................... 5-3 Image Quality Indicators ............................................. 5-4 Digital Images ............................................................ 5-8 Evaluation of Digitized Film Images—ASME Section V, Article 2, Mandatory Appendix VI ............................ 5-9 Evaluation of Phosphor Imaging Plate Images—Article 2, Mandatory Appendix VIII ............................ 5-11 Digital Image Processing ........................................... 5-13 

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Discontinuity Indications .................................................. 5-15 ASME Section XI Acceptance Criteria ............................... 5-15 

Section 6:  Process for Interpretation of Magnetic Particle Indications .................................. 6-1 

Section 7:  Process for Interpretation of Liquid Penetrant Indications ............................... 7-1 

Section 8:  Conclusions ............................................. 8-1 

Section 9:  References ............................................... 9-1 In-Text Citations ............................................................... 9-1 Bibliography .................................................................... 9-2 

Appendix A:  Example PDI Generic Procedure Evaluation Guidance ................................ A-1 

Appendix B:  Example Utility ISI Indication Decision Trees .......................................... B-1 

Appendix C:  Example Utility Contingency Plans ..... C-1 

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List of Figures

Figure 2-1 Fundamental NDE evaluation process ...................... 2-2 

Figure 3-1 The ultrasonic characteristics of fabrication flaws and cracks ...................................................................... 3-1 

Figure 3-2 The initial, qualified UT examination detects the cracks and also fabrication defects that look like cracks ....... 3-2 

Figure 3-3 Detailed analysis eliminates most of the false calls, while retaining the correct crack detections ................. 3-3 

Figure 3-4 Decision tree for manual ultrasonic weld examination indication resolution ....................................... 3-4 

Figure 3-5 Ultrasonic beam redirection .................................... 3-8 

Figure 3-6 Example fabrication flaw UT data .......................... 3-10 

Figure 3-7 Logic path for the evaluation of fabrication-related flaws detected during an in-service volumetric examination .................................................................. 3-20 

Figure 4-1 ASME Section XI, single flaws ................................. 4-5 

Figure 4-2 ASME Section XI, aligned linear flaws—1 > 2 (1 is greater than or equal to 2) ............................................ 4-5 

Figure 4-3 ASME Section XI, nonaligned parallel flaws—1 > 2, s is less than or equal to 1 ......................................... 4-6 

Figure 4-4 ASME Section XI, overlapping parallel flaws ............. 4-6 

Figure 4-5 ASME Section XI, overlapping flaws ........................ 4-6 

Figure 4-6 ASME Section XI, non-overlapping flaws—1 > 2 ...... 4-6 

Figure 4-7 ASME Section XI, multiple parallel flaws ................... 4-7 

Figure 4-8 Summary of ASME Section XI, linear flaw proximity requirements ...................................................... 4-7 

Figure 4-9 ASME Section XI, Table IWB-3510-3 ....................... 4-8 

Figure 4-10 ASME Section XI, Table IWB-3518-2 ..................... 4-9 

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Figure 4-11 ASME Section XI, Table IWB-3510-2 ................... 4-10 

Figure 5-1 ASME Section V, Article 2, Table T-283 ................... 5-4 

Figure 6-1 Fundamental NDE evaluation process ....................... 6-3 

Figure A-1 Indication evaluation flow chart .............................. A-6

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Section 1: Introduction Background

Thousands of nondestructive evaluations (NDEs) are performed every day around the world. The results of these examinations significantly contribute to a safer world. Additionally, these examinations help to reduce costs in the production, maintenance, and operation of components and structures.

Hundreds of NDEs are successfully conducted every year at operating nuclear power plants, but recent industry operating experiences have identified several instances in which improper flaw characterizations led to the initial misinterpretation of ultrasonic data containing fabrication-related discontinuities. A number of factors have been identified that contributed to the initial misinterpretation of these indications, including improved examination detection sensitivity, the use of more performance-based qualified systems (personnel, equipment, and procedures), and the focus on surface-connected service-induced discontinuities. The most recent reported operating experience continues to be based on ultrasonic testing (UT) of dissimilar metal welds (DMWs) in reactor piping systems; however, this issue centered on not detecting the discontinuities rather than improper interpretation. Efforts are underway to address this issue based on the root cause analysis of the missed detection. In addition to ultrasonics, other NDE methods are required to examine nuclear power plant components. This report is being updated and expanded to address NDE methods in addition to ultrasonics. These other methods are liquid penetrant, magnetic particle, and radiographic examination.

This report provides the steps and decision trees for processing manual UT, liquid penetrant, magnetic particle testing, and radiographic NDE data to effectively characterize, evaluate, and disposition indications detected in nuclear power plant piping, including DMWs. There are certain fundamental steps that apply to all NDE method indications. These fundamental steps will be detailed, in addition to the specific steps unique to the manual UT, liquid penetrant, magnetic particle testing, and radiographic NDE methods for fabrication and in-service indications in nuclear power plant components. The steps detailed herein are based on licensees who are required to comply with the American Society for Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, as conditioned by the U.S. Nuclear Regulatory Commission (NRC), Title 10 Code of Federal Regulations (10CFR), Part 50.55(a). Other licensees will find the report useful but might need to adapt it to their specific code(s) and regulatory requirements.

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A number of prior guidelines have been developed to assist in the detection of service-induced discontinuities. The industry has recognized the need for an additional guide to assist utility and service provider NDE personnel, plant management, regulators, and other stakeholders in the process of indication evaluation. This updated report includes generic indication evaluation information for the UT, radiographic, magnetic particle, and liquid penetrant examination methods. For ultrasonic indications, the focus is on discrimination of surface-connected in-service discontinuities from embedded fabrication discontinuities. In addition to this report, the Electric Power Research Institute (EPRI) has produced samples containing embedded fabrication flaws, and may develop additional samples, to better prepare UT examiners to distinguish between fabrication discontinuities and surface-connected service-related discontinuities. The proper interpretation of any NDE indication includes the review of more data than those provided by the initial examination that detects the indication. If this process is not properly followed, an inefficient response to the initial indication can ensue. It should be noted that this report does not invoke any Nuclear Energy Institute (NEI) 03-08, Revision 1, Guideline for the Management of Materials Issues, requirements at this time.

Utilities can significantly improve the indication interpretation process by proactive advance planning prior to performing any NDEs. Preparations should be made in advance as to how relevant indications will be addressed if detected. Based on a review of a number of utilities’ in-service inspection (ISI) programs, some develop detailed pre-examination ISI packages that contain all of the recommended information and make this available to the examiners, while others do not. This difference in approach is, in some cases, a philosophical issue.

The bottom-up information-processing approach addressed in cognitive theory is to have examiners conduct and report results based only on the NDE indications detected with no prior knowledge of previously reported discontinuities. In bottom-up processing, data are considered on their own merits without preconceptions or expectations. The top-down information-processing approach is to have examiners armed with more information about the item to be examined prior to performing the examination so that, if they detect indications, they can make a more informed interpretation of detected indications at that point in the process. There are advantages to both approaches. In either approach, interpretation of detected indications should not be made prematurely. As addressed in the EPRI report Cognitive Correlates of Ultrasonic Inspection Performance (NP-6675), one of the most important elements of inspection success is “avoidance of reaching conclusions early in the inspection process, before all available information has been obtained and considered” [1].

During the fabrication and construction of nuclear power plants components, discontinuities result as an integral part of the material fabrication and construction processes. The applicable codes and specifications provide requirements for the type, number, size, and location of allowable discontinuities; they do not require that the materials are discontinuity-free. These codes and specifications specify certain NDE methods to be used to detect discontinuities. These codes and specifications do not require that all of the detected discontinuities be removed.

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Fabrication flaws not detected or removed in accordance with ASME Section III, Rules for Construction of Nuclear Facility Components, or other applicable codes or specifications are routinely detected by preservice or in-service NDE methods. As examination sensitivity has increased, detection of fabrication-related defects has also increased. Examiners should be trained to recognize and properly characterize these fabrication flaws, as well as in-service ones.

The characterization, interpretation, and evaluation of NDE indications are complex. They can be compared with the systematic differential diagnosis process used by physicians, which begins by considering the most likely diagnosis first. Examiners collect and assemble the evidence and, based on knowledge and experience, eliminate all of the discontinuity types that could not produce the indication(s) and converge to the one with the highest probability of causing the indication(s).

Two specific operating experiences have highlighted the importance of following the entire evaluation process to its conclusion. Each was a UT examination of a DMW by a Performance Demonstration Initiative (PDI)-qualified examiner using a PDI-qualified procedure and equipment. Section XI of the ASME Code contains the rules for ISIs of nuclear plant components. The general requirements for qualification of NDE personnel contained in Section XI, IWA-2300, are amended by Section XI, Appendix VIII. Appendix VIII describes the additional requirements for performance demonstration of UT examination systems that integrate personnel, equipment, and procedures into a single entity. ASME Code Section XI, Appendix VIII, also includes 14 supplements that contain specific instructions for the conduct of performance demonstrations, including specimen requirements, conduct of performance demonstration, and acceptance criteria. A more recent operating experience, detailed in the following, reemphasizes the critical nature of initial detection of discontinuities:

During a manual examination of a nozzle weld in the St. Lucie Nuclear Power Plant’s retired pressurizer in February 2008, extensive indications were detected with an initial interpretation of possible cracking. Because the examination was conducted as a research activity on a component not in service, no urgency was attached to completing the detailed analysis required by the examination procedure. The regulator determined that the indications raised significant safety concerns to the extent that consideration was given to shutting down eight similar operating plants for expedited examination. Subsequent completion of the procedure’s indication interpretation process showed that the indications were a result of structurally benign fabrication defects.

An indication was reported in a pressurizer safety relief nozzle-to-safe-end DMW during the March 2010 refueling outage at Calvert Cliffs Nuclear Power Plant. The initial interpretation was that the indication showed the presence of cracking; this raised great industry and regulatory interest because the weld had previously been mitigated using a stress improvement process, and cracking should have been impossible. Large efforts and expenditures were incurred in preparation for removal and repair of the weld, while the completion of the indication interpretation process proceeded in parallel. Ultimately, the indication was interpreted to be the result of structurally benign fabrication defects.

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On March 24, 2012, at 1855 hours, with Unit 1 in Mode 6, refueling, two through-wall cracks were identified after machining the Unit 1 B steam generator (SG) hot leg nozzle. The defects were identified after machining approximately 0.7–1.1 in. (17.78–27.94 mm) of material from the nozzle-to-safe-end weld in preparation of full structural weld overlays. Machining of the nozzle was necessary in order to eliminate the taper, which would interfere with the final volumetric UT examinations. The material thickness of the DMW after final machining was approximately 4.1 in. (104.14 mm). Because the leakage from the DMW was not noticed until completion of the machining process (because of masking effects of the machining oils and lubricants), the exact through-wall lengths of the cracks are unknown. However, based on visual and surface examinations, the two through-wall cracks were axially oriented and fully contained within the Alloy 82/182 DMW. Also, it was concluded that the cracks did not propagate through the entire weld based on the as-found condition of the pipe (for example, no boric acid). Further investigation, using conventional manual UT examination methods, located the two through-wall cracks, as well as three additional indications with varying degrees of propagation. No unacceptable indications were identified in the A or C hot leg nozzle DMWs (post-machining) using conventional UT methods [2].

During manual UT examination conducted in September 2012 of 12-in. [304.8-mm] diameter, schedule 80 (t =0.687 in. [17.45 mm]) ferritic welds in N4 feedwater nozzles at an international member’s plant, several indications were interpreted to be cracking. Prior to beginning commercial operation, all four N4 feedwater nozzles were field modified to incorporate a new thermal sleeve design. This field modification included the replacement of the original stainless steel safe end with carbon steel components. After the modifications were complete, in addition to radiographic examinations, fully automated UT examinations were performed. Root geometry was recorded during the UT examination of all four safe-end-to-pipe similar metal ferritic welds. During the 2012 manual UT in-service examinations performed, crack-like linear indications were reported in all four feedwater safe-end-to-pipe similar metal ferritic welds. The unexpected reporting of significant crack-like indications in ferritic welds, which have no known damage mechanism, prompted the utility to perform radiographic examinations of all four welds. The results of these radiographic examinations were reviewed by the utility and their vendor and compared with the construction radiographs from the 1990s. The indications were again determined to be acceptable slag and heavy root convexity. The radiographs also showed that the ultrasonic indications were in the same areas as the radiographic indications. The radiographs were sent to EPRI for digitization and an independent review, which again confirmed that the indications were embedded slag inclusions and heavy root reinforcement. The inspection vendor then performed an encoded automated UT examination on the four welds that more precisely identified the indication locations as root geometry and interpass slag. EPRI personnel reviewed this new encoded data in Charlotte, North Carolina, and on-site personnel performed a manual examination of

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the indication locations. EPRI’s evaluation of the 2012 encoded examination data confirmed the presence of the indications identified during the manual UT examinations; however, the increased characterization capabilities of the encoded examination technique indicated that the most likely origin of the reported indications was several embedded fabrication flaws contained within the weld that were accompanied by an unusual inside surface condition. The inside surface condition yields significant responses that, in most instances, are readily identifiable from only one side of the ferritic weld. These inside surface responses are not consistent with service-induced planar flaws because these responses are not readily identifiable from both beam directions. The response’s significant amplitude and favorability for detection from only one beam direction indicate that a significant asymmetric ultrasonic reflector near the weld root is the most likely origin of the observed responses. Weld mismatch, which can be difficult to identify using radiographic techniques, and a nonconsumed insert are examples of asymmetric reflectors that can produce responses similar to those identified during the 2012 UT examinations.

These occurrences reemphasize one of the most important elements of inspection success, as mentioned previously: “avoidance of reaching conclusions early in the inspection process, before all available information has been obtained and considered” [1]. All personnel involved in, or potentially impacted by, the interpretation of detected indications should understand that it takes time and diligence to arrive at the proper results. During this time, licensees often find it prudent to initiate parallel activities in case further engineering analysis, repairs, replacement, or other appropriate remedies are required. Some utilities have contingency plans in place prior to performing examinations to address these potential occurrences.

EPRI’s 2009 Nondestructive Evaluation: Guideline for Conducting Ultrasonic Examinations of Dissimilar Metal Welds (1018181) was developed in response to industry issues regarding the performance of DMW examinations [3]. The report identifies many best practices for licensees and NDE service vendors in preparing for successful examinations of DMWs. The report provides one “Needed” requirement and six “Good Practice” recommendations in accordance with NEI 03-08, Revision 2, Guideline for the Management of Materials Issues [4]. The “Needed” requirement is to develop and implement a surface condition assessment and improvement process for DMWs.

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Glossary

The following terms are based on industry codes and standards. In some instances, the same term is defined slightly differently in these reference documents. In such instances, the ASME Section XI or Section V term is listed.

acceptable quality level. The maximum percent defective or the maximum number of units defective per hundred units that, for the purpose of sampling test, can be considered satisfactory as a process average [5].

calibration. The comparison of an instrument with, or the adjustment of an instrument to, a known reference(s) often traceable to the National Institute of Standards and Technology [5].

crack tip. The extremity of the flaw; the boundary between the flaw and the adjacent material at the intersection of the two flaw faces [6].

critical flaw size. The flaw size that will cause failure under a specified load calculated using fracture mechanics. The minimum critical flaw size for normal or upset conditions (Service Level A and B) is ac; the minimum critical initiation flaw size for emergency and faulted conditions is ai [6].

defect. A flaw (imperfection or unintentional discontinuity) of such size, shape, orientation, location, or properties as to be rejectable [6].

discontinuity. A lack of continuity or cohesion; an interruption in the normal physical structure of material or a product [6].

dissimilar metal weld. A weld between (a) carbon or low alloy steels to high alloy steels, (b) carbon or low alloy steels to high nickel alloys, or (c) high alloy steels to high nickel alloys [6].

evaluation. A review, following interpretation of the indications noted, to determine whether they meet specified acceptance criteria [7].

examination. A procedure for determining a property (or properties) or other conditions or characteristics of a material or component by direct or indirect means [5].

false indication. A nondestructive testing indication that is interpreted to be caused by a condition other than a discontinuity or imperfection [5].

flaw. An imperfection or unintentional discontinuity that is detectable by nondestructive examination [6].

flaw characterization. The process of quantifying the size, shape, orientation, location, growth, or other properties of a flaw based on NDE response [7].

imperfection. A condition of being imperfect; a departure of a quality characteristic from its intended condition [6].

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indication. The response or evidence from a nondestructive examination. An indication is determined by interpretation to be relevant, nonrelevant, or false [6].

in-service examination. The process of visual, surface, or volumetric examination performed in accordance with the rules and requirements of this Division [6].

in-service inspection (ISI). Methods and actions for assuring the structural and pressure-retaining integrity of safety-related nuclear power plant components in accordance with the rules of this Section [6].

inspection. A procedure for viewing or observing visual characteristics of a material or component in a careful, critical manner [5].

interpretation. The determination of whether indications are relevant, nonrelevant, or false [7].

laminar flaw. Planar flaws that are oriented within 10° of a plane parallel to the surface of the component (See Fig. IWA-3360-1) [6].

linear flaw. A flaw having finite length and narrow uniform width and depth (See Fig. IWA-3400-1) [6].

method. One of the disciplines of NDE; for example, ultrasonic testing, within which various test techniques may exist [8].

nondestructive examination (NDE). An examination by the visual, surface, or volumetric method [6].

nondestructive examination. See nondestructive testing [5].

nondestructive evaluation. See nondestructive testing [5].

nondestructive inspection. See nondestructive testing [5].

nondestructive testing (NDT). The development and application of technical methods to examine materials or components in ways that do not impair future usefulness and serviceability in order to detect, locate, measure, and evaluate flaws; to assess integrity, properties, and composition; and to measure geometrical characteristics [5].

nonplanar flaw. A flaw oriented in more than one plane. It can be curvilinear or a combination of two or more inclined planes (See Fig. IWA-3340-1) [6].

nonrelevant indication. An NDT indication that is caused by a condition or type of discontinuity that is not rejectable. False indications are nonrelevant [7].

planar flaw. A flat two-dimensional flaw oriented in a plane other than parallel to the surface of the component (See Fig. IWA-3310-1) [6].

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relevant condition. A condition observed during a visual examination that requires supplemental examination, corrective measure, correction by repair/replacement (R/R) activities, or analytical evaluation [6].

relevant indication. An NDT indication that is caused by a condition or type of discontinuity that requires evaluation [7].

test. A procedure for determining a property or characteristic of a material or a component by direct measurement. Examples include mechanical tests to determine strength, hardness, or other property; determination of leakage (a leak test); or checking the performance (function) of a piece of equipment [5].

test technique. A category within an NDT method—for example, immersion ultrasonic testing [8].

true indication. An NDT indication that is caused by a discontinuity. True indications can be either relevant or nonrelevant.

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Section 2: General Considerations for Evaluation of NDE Indications

Interpretation, Characterization, and Evaluation

All involved should understand and use the proper terminology. The American Society for Testing and Materials, ASME, American Society for Nondestructive Testing, and others have developed and published definitions for terms used in NDE. Some of these terms are included in the glossary in Section 1. The glossary is extensive; selected key definitions are repeated here. It might be instructive to review the following while considering Figure 2-1:

A discontinuity is a lack of continuity or cohesion, an intentional or unintentional interruption in the physical structure or configuration of a material or component [6].

The evidence of a discontinuity by an NDE method is called an indication [6]. The indication has to be interpreted to determine whether it is a relevant, nonrelevant, or false indication.

– A false indication is an NDE indication that is interpreted to be caused by a condition other than a discontinuity or imperfection [5]. A signal on a UT instrument screen caused by electromagnetic interference from a motor would be an example of a false indication.

– A UT signal from a counterbore bevel in a piping butt joint with a full penetration groove weld would be an example of a nonrelevant indication. Because the weld joint is designed to include a counterbore (a counterbore is a discontinuity), this condition would not considered rejectable even if it exceeded the established acceptance criteria. Indications from metallurgical interfaces, such as weld fusion zones, also are nonrelevant indications.

– Relevant indications are responses from flaws. A UT signal from a slag inclusion (another discontinuity) in a shielded metal arc weld is an example of a relevant indication. Signals from service-induced cracking also are relevant indications.

A flaw is an imperfection that might be detectable by nondestructive testing and is not necessarily rejectable [6].

Relevant indications require characterization and evaluation.

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Flaw characterization is the process of quantifying the size, shape, orientation, location, growth, or other properties of a flaw based on its NDE response [7].

Evaluation is a review, following interpretation and characterization of the indication, to determine whether the discontinuity meets specified acceptance criteria [7].

Figure 2-1 Fundamental NDE evaluation process

In order for an NDE examiner to make the proper interpretation as to whether an indication is false, nonrelevant, or relevant requires considerable knowledge, skill, and experience. This knowledge includes not only the NDE method that is applied but also detailed information on the component and its potential associated discontinuities. In the example of the nonrelevant indication resulting from counterbore, if the examiner had not been aware of the detailed weld procedure, the UT indication could have been misinterpreted as a relevant indication resulting from a lack of penetration in the weld root.

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After an indication is interpreted as relevant, it must be characterized. Determining the flaw characteristics from the NDE data and knowledge of the material and processes that caused it is essential to proper evaluation. Evaluation determines whether the flaw is acceptable in accordance with the applicable Code or specification acceptance criteria. For example, in most construction codes applicable to welds, cracks, lack of fusion, and lack of penetration are unacceptable regardless of other characteristics, such as size, shape, orientation, and location. Other relevant indications, such as porosity, slag, and tungsten inclusions, could be acceptable based on their characteristics. Appendix B provides examples of how two utilities address detected indications.

In addition to parameters of the method and technique used to reveal the indication, knowledge and experience of the material and process and their related discontinuities are essential in making a correct interpretation and characterization of the discontinuity. As stated in When Are Weld Defects Rejectable?:

Because increasingly more sensitive inspection tools and techniques are revealing more defect indications, it must also be strongly emphasized in the training of inspectors that “perfect” materials do not exist. Therefore, a sound training program should include consideration of common defects and their relation to service performance of the component involved. Very little has been published on this.

A training program should also cover the “detectability” of defects. Just because a component has passed inspection by radiography or ultrasonics does not mean that it does not contain defects that will lead to failure.

There are too few inspectors who have a knowledge of metallurgy or understand the specific melting, forming, shaping, welding and heat treating operations involved in the production of the component being inspected. [9]

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Section 3: Process for Interpretation of Manual Ultrasonic Indications

The interpretation of NDE indications in DMWs requires careful and methodical application of a process to ensure a high probability of achieving the correct results. It is a two-stage process designed to, first, minimize failures to detect cracking and, second, to minimize false calls (incorrectly interpreting fabrication defects as being cracks).

The ultrasonic characteristics of fabrication defects and of cracks usually are distinct, but there is some overlap; some fabrication defects, or networks of fabrication defects, can appear cracklike, as illustrated conceptually in Figure 3-1.

Figure 3-1 The ultrasonic characteristics of fabrication flaws and cracks

The first step in the two-stage process is examination of the weld by a qualified examiner using a qualified procedure. The qualification process, conducted in accordance with ASME Section XI, Appendix VIII, as conditioned by regulation, focuses on ensuring that the procedure, equipment, and examiner do not miss cracks; it does not focus on fabrication defects. Therefore, the effect of the initial, qualified examination is shown in Figure 3-2: cracking is detected,

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along with fabrication defects that have crack-like ultrasonic characteristics. (As shown in Figure 3-2, manual and encoded examinations are effective for crack detection, but encoded examinations provide images that make it easier to discriminate fabrication flaws.) If a crack-like indication is detected, the second step is executed.

Figure 3-2 The initial, qualified UT examination detects the cracks and also fabrication defects that look like cracks

The second step of the two-stage process is a highly detailed analysis focused on making the final discrimination as to whether the indication represents cracking or fabrication defects that have ultrasonic responses similar to cracking. It includes consideration of the weld’s fabrication, service, and inspection history; independent analysis of the UT data; and consideration of opportunities to obtain additional NDE data to support the analysis. The effect of this detailed analysis is shown in Figure 3-3: most of the potential false calls are eliminated, while retaining correct interpretations of actual cracking.

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Figure 3-3 Detailed analysis eliminates most of the false calls, while retaining the correct crack detections

Figure 3-4 illustrates this process. Figure 3-4 might be useful to all stakeholders who are involved in or affected by the examination, such as the utility’s outage control center, interested industry groups such as the Materials Initiative, and the NRC. Stakeholders should understand the following key points:

The successful use of this process requires knowledge of the material; the weld configuration and process; weld fabrication records including radiographs and repair records, service history, results of prior UT examinations, and other NDE method results; and any other pertinent information. In most cases, only the licensee can provide this information.

Each of the process and decision boxes represents a significant amount of information that must be properly assessed to proceed to the next point. It takes time. Short-circuiting or abbreviating the process or failing to provide all available information reduces reliability.

After the initial examination by the qualified examiner, the process is a team effort. Additional NDE service vendor personnel, utility NDE and supporting personnel, and, at the utility’s discretion, outside industry expertise all might be engaged.

This section provides guidance on how to ensure that the information needed to make the best decision at each point is available, reviewed, and properly analyzed to achieve a correct result.

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Figure 3-4 Decision tree for manual ultrasonic weld examination indication resolution

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Prior to conducting a manual UT examination of a weld, a significant amount of information should be collected. Some of this information is essential to performing a proper examination, and some information is not essential initially; however, it might be required if a true indication is detected. Even more information might be required to make the proper evaluation if it is determined that a relevant indication has been detected. The utility’s examination information processing philosophy, bottom-up or top-down, will determine when all of this information will be provided to the UT examiner.

For ASME Section XI, Appendix VIII, examinations, the utility must review the procedures and the individual examiner’s Performance Demonstration Qualification Summary (PDQS) must be performed to ensure that the examiner, equipment, and procedure are qualified to perform the assigned examination. If using a PDI generic qualified procedure, additional detailed guidance is included in Appendix A.

As a minimum, for a top-down information processing approach, the ultrasonic examiner should be provided the following:

Plant and component drawings, sufficient to allow the examiner to properly find and identify the component to be examined

The approved UT procedure to be used to perform the examination of the specific component

The component material, dimensions—that is, diameter and thickness—and profile data

The procedure for reference points and scan patterns (if not provided in the UT procedure)

The procedure for documentation of calibration and data recording (if not provided in the UT procedure)

If ASME Section XI, Appendix VIII, is applicable, the following are required:

An approved Appendix VIII procedure applicable to the material type, diameter, and thickness ranges specified

The qualification limitations listed on the PDI PDQS

Information on qualified search units and instruments and the qualified essential variables—that is, instrument settings to be used during the examination (usually provided in a PDI procedure Table 1 and Table 2 format)

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Many utilities conduct a prejob briefing prior to conducting each examination, often using a detailed prejob checklist. The briefing package typically includes a system isometric drawing with the component to be examined highlighted and, if applicable, a detailed component drawing. Some plants provide photographs of the general area; the component and access provisions and limitations, if applicable; radiation protection requirements and general and contact radiation levels; and any other relevant information needed to perform the examination.

The following additional information should be accumulated prior to performing an examination to avoid delays in making a proper interpretation and evaluation of indications. (Step 5, UT Level III Review, includes a detailed discussion of each item. In some cases not all of the desired information is available, complete, or of useful quality.)

Fabrication records

Current NDE UT data results

UT oversight

Prior UT examination data (including raw encoded ultrasonic data, if available)

Radiographs

Supplemental NDE results

Service history information

EPRI’s Nondestructive Evaluation: Guideline for Conducting Ultrasonic Examinations of Dissimilar Metal Welds (1018181) [3] provides extensive guidance for utilities and NDE service vendors in preparing to perform UT of DMWs. The purpose is to minimize the occurrence of significant human errors while maximizing the probability of a smoothly executed outage with completion of the planned scope. The nuclear power plant owner is responsible for compliance with one “Needed” requirement and for evaluation of six “Good Practice” recommendations in accordance with NEI 03-08, Revision 2 [4]. The “Needed” requirement is to develop and implement a surface condition assessment and improvement process for DMWs. The guideline specifically targets DMWs, but its recommendations are largely applicable for other components that require an Appendix VIII-qualified examination.

It is recommended that the detection of in-service indications be factored into the outage schedule. The ISI program manager and/or the NDE Level III personnel should provide this input to the outage management team. The potential to detect flaws has increased because of increased examination sensitivity, use of performance-based qualified procedures, and other measures. Prudent provisions in outage scheduling, including the potential to impact critical path, are desirable.

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The weld must be examined in accordance with a procedure, by an examiner who is qualified to use it. The examination procedure includes instructions for conducting the initial examination represented by this box in the flow chart and also contains instructions for subsequent interpretation and evaluation of detected indications. For DMWs in the primary cooling system piping, the qualification requirements are defined in ASME Section XI, Appendix VIII. The qualification addresses only the aspects of the procedure that will be executed by the examiner acting alone; it does not address the team effort of analyzing the mass of data involved in interpreting and evaluating indications.

All suspected flaw indications, regardless of amplitude, should be investigated to the extent necessary to provide accurate characterization, identity, and location. Additional scanning (relooks) with qualified equipment is acceptable.

All suspected flaw indications should be plotted on a cross-sectional drawing of the weld. It is a common practice to collect thickness measurements and replicate the weld contour at four locations approximately 90° apart around the pipe circumference and use these data to develop cross-sectional profiles; these data might already be available from the preservice inspection or prior ISI examinations. These profiles might not be representative of the cross-sectional profile at the azimuthal location where an indication is located. The profile data should also be verified to represent the current as-built condition. Weld repairs and surface conditioning of the weld and adjacent base metal might have been performed after the thickness and contours data were initially taken. Therefore, it is a good practice to take thickness measurements and weld contour data at the indication location to ensure that they are correct.

The accurate location of the reflector is one of the major considerations in the correct identification of an indication. The location of the reflector should be determined by plotting. The accuracy of the plot reflects the accuracy of the ultrasonic data and the weld configuration data. Variations within the material, such as acoustic velocity and prevalent grain orientation, also can affect the accuracy of the indication plot. Figure 3-5 illustrates the error that can result from plotting beams as straight lines.

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Figure 3-5 Ultrasonic beam redirection

All indications produced by reflectors within the volume to be examined that can be attributed to the geometry of the weld configuration should be considered as nonrelevant indications. Nonrelevant indications can be verified by the use of radiographs, as-built drawings, fabrication records, prior UT examination data, and supplemental NDE results. For example, the construction radiographic report could reveal the weld root in the same location that the indication plots. Additionally, the preservice UT report and previous in-service UT examination data could document an acceptable reflector in the same location.

Guidance in PDI-UT-10 (see Appendix A) is typical of that found in qualified procedures.

All suspected nonrelevant indications should be investigated and evaluated, taking into account the following indication characteristics, which should not be considered as mandatory criteria for classifying indications as nonrelevant but are listed as significant points of interest for the examiner to consider during evaluation of suspect areas:

The indication appears at or near the centerline of the weld or other documented geometrical condition and can be seen continuously or intermittently along the length of the weld at consistent amplitude and time base positions. This characteristic can be supported by obtaining localized thickness and surface contour recordings at the location of the indication(s).

The indication provides additional responses, which occur from the same scan position but at different time base positions (multiples) along the length of the weld. This could be a sign of mode-converted shear-wave signals from counterbore or similar geometric reflectors. This characteristic can require an increase in time base size in order to observe these responses.

The indication can be seen across the entire length of the scan, either continuously or intermittently, at consistent amplitude and time base positions. This characteristic can be supported by scanning along the indication length laterally.

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The indication provides minimal echo-dynamic travel (walk). This characteristic can be supported by observing other areas along the length of sample and through the use of an adequate reference reflector (an inside surface notch or equivalent).

The signal responses are consistent from each side of the weld for axial scans or from each direction (clockwise or counterclockwise) for circumferential scans.

All indications produced by reflectors within the volume to be examined, regardless of amplitude, that cannot be clearly attributed to the geometrical or metallurgical properties of the weld configuration should be considered as relevant (flaw) indications.

If all of these data or the large majority of the data supports the indication being nonrelevant, there is a high probability that this is the correct interpretation.

If none or only a portion of the evidence supports a conclusion that the indication is nonrelevant, it is a potential relevant indication. It is a good practice for a second individual to review the data, a certified UT Level III professional with current knowledge and experience and, ideally, qualified to the same procedure. Some of the interpretation of the current UT data as detailed below might include evaluation of relatively subtle features of the ultrasonic signals and their response to the reflector. The 2010 EPRI report Appendix VIII, Supplement 10 and 12 Training (1021236) includes detailed examples of how the subtle indication features are presented and can be interpreted [10]. The 2010 EPRI report Advanced Nuclear Technology: Reduction of American Society of Mechanical Engineers III Weld Fabrication Repairs—Fitness for Purpose (1021181) includes a number of detailed examples of ultrasonic indications of ISI and fabrication flaws and their UT responses [11]; one example is shown in Figure 3-6. These references might aid the examiner in interpreting the indication.

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Figure 3-6 Example fabrication flaw UT data

Guidance in PDI-UT-10 (see Appendix A) is typical of that found in qualified procedures.

All suspected flaw indications should be investigated and evaluated taking into account the following indication characteristics, which should not be considered as mandatory criteria for classifying indications as flaws but are listed as significant points of interest for the examiner to consider during evaluation of suspect areas.

The indication has a good signal-to-noise ratio with defined start and endpoints. This characteristic can be supported by observing signal-to-noise ratio variation along the length of the component.

The indication plots to a location susceptible to cracking. This characteristic can be supported by obtaining localized thickness and surface contour recordings at the location of the indication(s).

The indication provides substantial and unique echo-dynamic travel (walk). This characteristic can be supported by observing other areas along the weld length and through the use of an adequate reference reflector (an inside surface notch or equivalent).

Several areas of unique amplitude peaks are observed throughout the indication length. This characteristic can be supported by observing other areas along the weld length and by scanning along the indication length laterally.

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Inconsistent time base positions are observed throughout the indication length. This characteristic can be supported by scanning along the indication length laterally.

The indication shows evidence of flaw tip signals.

Circumferential indications provide axial components while performing tangential scans.

The indication(s) can be confirmed from the opposite direction. This characteristic is dependent upon flaw orientation and configuration and might not always be available.

The indication(s) can be confirmed with an additional examination angle. This characteristic is dependent upon flaw orientation and configuration and might not always be available.

For components where access is limited to a single side of the component, the following additional information should be considered: as a result of the uncertainties associated with sound propagation through austenitic weld material and buttering, actual flaw positioning, and the true thickness of the component, an accurate inside diameter (ID) connection on the far side of the weld might be unobtainable. For suspect far side flaw indications, several search unit parameters (for example, lower frequencies, different angles, and different focal depths) should be evaluated to optimize response.

If all of these data or the large majority of the data supports an indication as being relevant, there is a high probability that this is the correct interpretation: the indication is from a flaw.

If all of these data or the large majority of the data supports the indication being nonrelevant, there is a high probability that this is the correct interpretation.

Potential Relevant Indication

If a review of the UT and other data does support the interpretation of a potential relevant indication, the process should be followed as shown in Step 8. If this information was collected prior to the examination in the Prepare step (1), the review of it by knowledgeable and experienced certified Level III personnel can be initiated immediately. If the information was not collected during the Prepare step, additional time might be required. Because the collection and review of the data takes time, depending on the availability and quality, this process might require approximately two to seven days, as shown in Figure 3-4. It is understood that this could impact the outage critical path and that contingency plans should be implemented in parallel with the analysis process in the event an in-service flaw is confirmed.

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It should be clearly communicated to all stakeholders—that is, outage control center personnel, nuclear power plant management, interested industry groups, and the NRC—that firm conclusions about the potential relevant indication would be premature at this point in the process. Additional steps, as detailed below, are essential to reach a fully informed decision about the indication.

This part of the process—the detailed interpretation of the indication—often takes place in an atmosphere of high management interest because of the potential high cost and impact to outage scheduling. This high level of management attention has a number of effects on the interpretation process, not all of them positive from the NDE team’s perspective. They are as follows:

The examiner gets help. Additional technical resources from both the NDE service company and the utility are made available, both to collect information and to participate in interpretation. The utility might seek technical input from outside agencies, often from EPRI. The interpretation and evaluation process is now a team effort. This is a positive effect; the expertise of the individual qualified examiner identified a potential defect, but the final determination will be made with the benefit of the expertise of many.

The utility can begin aggressive contingency preparations for a possible repair or replacement. This necessary step might increase the pressure on the NDE team, because the utility and the repair vendor seek information on the potential flaw that will affect the repair design.

On occasion, a utility has considered its outage schedule and made the economic decision to forgo the detailed interpretation process for a potential relevant indication, opting to assume that the indication was due to cracking and to repair the weld immediately.

The utility might notify the NRC and industry groups of the potential existence of service-induced cracking. If the presence of cracking would have potential generic implications, regulatory and industry interest would be immediate and high, with multiple conference calls per day and perhaps with industry technical groups preparing contingencies. The utility provides frequent updates for these groups, again creating pressure for the NDE team to provide conclusions.

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The interpretation evaluation process will move most efficiently if the NDE team is allowed to work with minimal interruption. All stakeholders should clearly understand that the initial inspection result is not the final answer—it is a preliminary reading. Stakeholders outside the utility also should understand that the fleet contains many more fabrication flaws than cracks and that mobilization of emergent industry activities might be premature at this point.

During this step, all current inspection information is reviewed in detail, along with all available supporting information detailed below. The purpose of the review is to validate the current NDE results and to determine the appropriate and optimum additional NDE data that should be obtained.

To minimize delays, it is strongly recommended that all the available information be accumulated prior to performing an examination. Information needed for each weld to be examined in addition to that for the top-down information processing includes the following:

Fabrication records

Current NDE UT data results

UT oversight

Prior UT examination data (including raw encoded ultrasonic data, if available)

Radiographs

Supplemental NDE results

Service history information

In some cases, not all of the desired information is recoverable, and some of it may not be of useful quality. However, every reasonable attempt should be made to assemble as much of the information as practical.

Fabrication Records

Fabrication information can indicate where nonrelevant indications might be expected and locations that might be more susceptible to in-service cracking. The information should include the following:

Detailed weld procedures

– Materials

– Weld joint preparation

– Welding process or processes

– Field weld or shop weld

– ID grinding

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Configuration

– Current configuration as determined by visual examination and profile data

– As-built drawings

– Original surface preparation

– Additional surface preparation since fabrication

Weld repairs

– Made during fabrication, construction, preservice, or in-service

– If weld repairs were not documented, a determination as to whether it is apparent from visual examination that weld repairs were performed

– Replacement of the original fabrication or construction weld, if applicable

Stress mitigation techniques performed on this weld

Current NDE UT Data Results

The following should be considered when evaluating the quality of the current NDE UT results and reports:

Clarity and conciseness

Quality of the current automated UT data (if applicable), particularly evidence of good probe contact

Thickness measurements and surface contours taken at the azimuth of the indication

Plotting accurate based on the recorded data

Surface preparation appropriate for the examination

Weld crown width, transition of the weld to base metal, diametric shrinkage, and so forth allow proper search unit coupling and required coverage

Qualified procedure was fully implemented

UT examiner qualified for this examination using this procedure

UT procedure appropriate for this examination

Component or configuration does not violate any qualification limitations or other special conditions to the procedure

Optimum qualified equipment was used for the examination

Actual examination coverage achieved

If 100% coverage was not achieved, coverage limitations documented in detail

The process by which the indication was determined to be ID-connected

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UT Oversight

The following should be considered when evaluating the UT oversight:

Manual reexamination by a different UT certified examiner

Encoded UT data reexamination

Full review of the indication data report by other qualified people or a Level III professional

Flowchart, checklist, or other similar process has been followed in the indication evaluation to ensure that all steps have been thoroughly addressed

Encoded UT data (if any) have been reviewed by additional qualified examiners

NDE Data from Prior Examinations

The following should be considered when evaluating the NDE data from prior examinations:

ASME Section XI preservice inspection UT and other NDE data

ASME Section XI, ISI UT data from prior outages

– Inspection written reports at minimum

– Surface profile at the time and its effect on coverage and examination effectiveness

– For encoded examinations, reanalyze raw data

o Ensure that hardware is available to read the archival data media and that software is available to analyze it

o Quality of the data (probe contact, scan limitations)

– Identify whether preservice inspection and/or prior ISI UT techniques were qualified and/or capable of detecting the indication now being evaluated

– Same indication was present in the previous reports or raw encoded data

o Review validity of the interpretation formed during the prior examination

o Changes in size, amplitude, and so forth that are not attributable to technique changes

o Stress mitigations applied since the prior examination

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Radiographs

The following should be considered when evaluating radiographs:

Recover the fabrication and/or construction radiographs

Condition of the radiographs

– Deterioration of quality during storage

– Film quality

Radiographic testing technique sheet and reader sheet

– Adequate documentation to understand how the weld was examined

– Reader sheet identifies indications that could have the same source as the potential flaws identified by the UT examination

Radiographic testing location stamps

– If they are still on the component, verify correlation with the UT reference points.

– If they do not correlate, reconcile the two sets of reference marks.

– Existing weld crown provides clues to validate the correlated and reconciled location reference markers.

– Transparent overlays (“skins”) available to validate the locations.

– Validated correct location and weld.

Review the radiographs

– Determine the degree to which the radiographic testing is applicable in assisting the current interpretation

– Level II or Level III certified radiographer available to read the radiographic testing film

– Radiographer verifies sufficient information is available to make a valid interpretation

– Assess the need for digitizing the film

– Determine presence of indications on the film in the area where the UT indication was reported

o Was it reported on the original reader sheet?

o Was it identified as acceptable or unacceptable?

o If unacceptable, was it repaired, and, if so, are the repair radiographs available (R-1, R-2 films)?

– Identify any weld rework (repairs, replacements, additional surface preparation, or stress mitigation) since the radiographic testing film was made

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Supplemental NDE

The following should be considered when evaluating the options and benefits of performing supplemental NDE to inform the interpretation.

Practicality of inside surface examinations (visual testing, eddy current testing, and liquid penetrant testing)

Zero-degree UT examination in the area of the indication

– Reflector detected within the wall of the component indicating an embedded flaw

– No zero-degree indication in the area of the suspect indication but with a reduction in the back-wall signal potentially indicating that a flaw is present

Manual UT reexamination by additional UT certified personnel

– Result using the original calibration and equipment

– Result using a new calibration and/or equipment

o Different UT search units, beam angles, instruments, and procedure

o Encoded UT using a qualified system (procedure, equipment, and personnel)

If the original examination was encoded, reexamination using the following:

– Slower scan speeds and finer increments

– Additional angles

– Manual examination to verify the auto data, using the same probe

Service History

The following should be considered when evaluating the service history:

Age of the component

Operating experience indicating susceptibility to a certain flaw type

Documented plant-specific operating experience that could indicate certain service-related damage mechanisms

– Chemical intrusion from leaking condenser tubes or SG tubes

– Mitigation methods that might not have been controlled as planned

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After a comprehensive analysis of all the relevant data derived previously, reach an informed final interpretation as to the nature of the indication.

The evaluation process and result supporting the nonrelevant indication decision should be comprehensively recorded so that it is available to support subsequent examinations.

During fabrication and construction of nuclear components designed and built to the built to the requirements of ASME Section III or other applicable codes and specifications, the results of the specified NDE is required to be documented. The applicable codes and specifications acceptance criteria might allow some discontinuities of certain sizes to remain in components. The fabrication and construction NDE documentation should include this information and might be useful as the evaluation basis for the detected indications. The following should be noted, however:

These records might be not be available.

If the records are available, they could have the indications not documented or not accurately documented.

Weld repairs might have been performed but not documented.

The NDE methods and techniques used in fabrication and construction might not have been as sensitive as those currently used.

Assuming that fabrication and/or construction NDE records are available and that they document the detection and acceptance by the applicable Code or specifications, document the current interpretation process and results. Reference the records of the ASME Section III or other applicable specification’s NDE

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that originally detected and accepted the flaws. This documentation should also include the ASME Section XI preservice inspection and ISI UT examination records. These records will serve as the basis for future ISI NDE monitoring of the reflector.

Fabrication defects confirmed and documented as acceptable in fabrication and/or construction NDE records and detected and documented in preservice inspection and/or ISI examination records will complete this step in the evaluation process.

ASME Section XI, Subarticle IWB-3500, Acceptance Standards, defines the allowable flaws in the various components required to be examined according to Subarticle IWB-2500—specifically, Paragraph IWB-3514, Standards for Examination Category B-F, Pressure Retaining Dissimilar Metal Welds in Vessel Nozzles, and Examination Category B-J, Pressure Retaining Welds in Piping, reference Table IWB-3514-1, Allowable Planar Flaws, for the maximum aspect ratio (a/l) for DMWs. Figure 3-7 provides a detailed example of the process for evaluation of a detected fabrication flaw.

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Figure 3-7 Logic path for the evaluation of fabrication-related flaws detected during an in-service volumetric examination

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If a fabrication flaw is determined to meet the applicable IWB-3500 acceptance standards, no additional action is required except to document the results in the ISI program. However, if a fabrication flaw is determined not to be acceptable to the applicable IWB-3500 acceptance standard, Section XI provides two options as defined in ASME Section XI, subparagraph IWB-3131(c), for final disposition of a flaw. These options are correction by a repair/replacement (R/R) activity or acceptance by analytical evaluation. The analytical evaluation will be addressed in more detailed below (see Step 16, Figure 3-4).

Document the results of the IWB-3500 evaluation in the ISI program records.

If a fabrication defect has been confirmed, was not documented in the fabrication and/or construction records, and does not meet the IWB-3500 acceptance standards, apply IWB-3600, Analytical Evaluation of Flaws, using the analytical procedures described in ASME Section XI, Nonmandatory Appendix A, Analysis of Flaws, to calculate its growth until the next inspection or the end of the service lifetime of the component. This option typically requires an engineering organization to be contracted to conduct the evaluation, and the area containing the flaw requires subsequent reexamination during the next three inspection periods. Also, the analytical evaluation could negatively impact the outage schedule, and, although rare, the analytical evaluation results could potentially be determined not to support continued operation without an R/R activity. If the results support continued operation, additional examinations are required for the next three inspection periods. Results supporting continued operation could also provide additional time to review R/R options versus the required reexaminations. The analytical evaluation and the R/R activities are subject to review by the authorized inspection agency and the applicable NRC branch. The development of contingency plans for contracting engineering analytical evaluations, organizations to perform R/R activities, and decision tree tools for making these decisions can greatly aid the nuclear power plant in the situations.

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Depending on the IWB-3600 Analytical Evaluation of Flaws results, the component may be acceptable for continued operation. As addressed in Step 16, if it is acceptable for continued service, reexamination is required over the next three subsequent inspection periods to ensure that the flaw is not growing. The analytical evaluation is required to be documented and is subject to regulatory review.

R/R activities require a detailed plan that is subject to regulatory review. A service provider with qualified repair procedure and personnel is required to perform these activities. Contingency planning can greatly assist in minimizing impact to the outage schedule if an R/R activity is required.

At this point in the indication evaluation process, contingency plans for relevant ISI defects should be implemented. Also, the utility should communicate to the NRC and to interested industry groups the confirmed detection of an in-service defect.

See Steps 14 and 16 for the details for the IWB-3500 evaluation that is required. Note that if the defect is determined to be stress corrosion cracking, IWB-3500 analysis is not allowed for those implementing the ASME Section XI 2007 and later editions; IWB-3600 analysis is required by the ASME Section XI 2007 and later editions.

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See Step 18 in Figure 3-4 for the details for the R/R activity. In certain cases, industry-accepted mitigation methods have been developed and implemented as an alternative to R/R activity. These include weld overlay repair, inlaying or onlaying corrosion-resistant clad, mechanical stress improvement process, and induction-heating stress improvement. Each of these has advantages and limitations and has to be considered on a case-by-case basis. Additionally, provisions for subsequent NDE have to be considered in the selection of the R/R activity or the mitigation method. Ideally, these would have been included in the contingency planning so that the technical information and availability of resources would be understood without delay. The R/R activity or mitigation approaches typically restore the component to the original design basis condition so that the item is returned to the regular ASME Section XI examination schedule.

If an ASME Section XI, IWB-3600, evaluation is used as detailed in Step 16 of Figure 3-4, the component is required to be reexamined on an expedited schedule for the next three periods to ensure that there is no flaw growth. If there is no change in the flaw size, the component can return to the regular examination schedule frequency.

After completion of Step 21 or Step 22 of Figure 3-4, the indication evaluation process is complete. Document the process and results in detail in the ISI program.

Contingency Plans

The INPO 06-008 Guidelines for the Conduct of Outages at Nuclear Power Plants, Revision 1, defines contingency plan as “an approved plan of compensatory actions to minimize the impact of work activity issues that could affect shutdown risk, schedule, budget, or production.Contingencies are developed to mitigate reductions in shutdown safety or impacts to the outage plan commensurate with the level of risk the activity poses” [12].

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This report provides detailed information on how to develop and implement outage contingency plans. Although the report does not specifically address NDE issues, it addresses elements such as preparation, execution, and improving performance that should be used by ISI and NDE personnel to prepare and implement an effective plan. Some utilities have developed and are implementing contingency plans for addressing the detection of ISI indications. Appendix C includes examples of these contingency plans.

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Section 4: General Consideration for Interpretation and Evaluation of Radiographic, Magnetic Particle, and Liquid Penetrant Indications

All NDE methods produce indirect indications of discontinuities. However, the indications do not directly reveal what the discontinuities are. The indications must be correctly interpreted before they provide the information as to the actual condition of the material. For example, a radiographic film displaying dark lines, spots, or density variations is meaningless until a knowledgeable, experienced radiographer interprets the indications.

Magnetic particle and liquid penetrant examination methods produce indications on the surface of materials that are rather clearly related to the size and shape of the discontinuity causing the indication. In fact, in some cases, when the discontinuity is at the surface, it can be directly seen after it is detected by the magnetic particle or liquid penetrant methods. Regardless, the indicaton still has to be interpreted to determine which type of discontinuity it is and characterized to assess its impact on the component usefullness.

In general, interpretation of an NDE indication means to make a decision as to what is the cause of the indication. As addressed in the glossary in Section 1 of this report, ASME Section XI defines interpretation as the determination of whether indications are relevant or nonrelevant. ASME Section XI, unlike many other codes and specifications, does not require the examiner to determine the type of discontinuity detected—that is, it does not require the distinction between crack, lack of fusion, cold shut, and so forth to evaluate the flaw to the acceptance criteria. For plant modifications and Repair/Replacement (R/R) activities, however, the construction Code requirements apply. As shown below from ASME Section III, Rules for Construction of Nuclear Plant Facilities, Division 1, Subsection NB, Class 1 Components, the examiner does have to characterize discontinuity indications to evaluate them to the acceptance standards. For example, for radiographic testing, “any indication characterized as a crack or zone of incomplete fusion or penetration”; for UT, “…the operator can determine the shape, identity, and location of all such imperfections and evaluate them…”; and for magnetic particle and liquid penetrant testing, “any cracks and linear indications.” Based on these requirements, the examiner must have the

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knowledge and experience to characterize indications resulting from base material product form discontinuities—that is, castings, forgings, rolled products, extrusions, drawn products, welds made with various welding processes, and in-service discontinuities.

ASME Section III NB-5300 ACCEPTANCE STANDARDS

NB-5320 RADIOGRAPHIC ACCEPTANCE STANDARDS

Indications shown on the radiographs of welds and characterized as imperfections are unacceptable under the following conditions:

(a) any indication characterized as a crack or zone of incomplete fusion or penetration;

(b) any other elongated indication which has a length greater than:

(1) 1/4 in. (6 mm) for t up to 3/4 in. (19 mm), inclusive

(2) 1/3 t for t from 3/4 in. (19 mm) to 2 1/4 in. (57 mm), inclusive

(3) 3/4 in. (19 mm) for t over 2 1/4 in. (57 mm)

where t is the thickness of the thinner portion of the weld;

(c) internal root weld conditions are acceptable when the density change or image brightness difference as indicated in the radiograph is not abrupt; elongated indications on the radiograph at either edge of such conditions should be unacceptable, as provided in (b) above;

(d) any group of aligned indications having an aggregate length greater than t in a length of 12t, unless the minimum distance between successive indications exceeds 6L, in which case the aggregate length is unlimited, L being the length of the largest indication;

(e) rounded indications in excess of that shown as acceptable in Appendix VI.

NB-5330 ULTRASONIC ACCEPTANCE STANDARDS

NB-5331 Fabrication All imperfections which produce a response greater than 20% of the reference level should be investigated to the extent that the operator can determine the shape, identity, and location of all such imperfections and evaluate them in terms of the acceptance standards given in (a) and (b) below.

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(a) Imperfections are unacceptable if the indications exceed the reference level amplitude and have lengths exceeding:

(1) 1/4 in. (6 mm) for t up to 3/4 in. (19 mm), inclusive

(2) 1/3 t for t from 3/4 in. (19 mm) to 2 1/4 in. (57 mm), inclusive

(3) 3/4 in. (19 mm) for t over 2 1/4 in. (57 mm)

where t is the thickness of the weld being examined; if a weld joins two members having different thicknesses at the weld, t is the thinner of these two thicknesses.

(b) Indications characterized as cracks, lack of fusion, or incomplete penetration are unacceptable regardless of length.

NB-5340 MAGNETIC PARTICLE ACCEPTANCE STANDARDS

a) Mechanical discontinuities at the surface are revealed by the retention of the examination medium. All indications are not necessarily defects, however, since certain metallurgical discontinuities and magnetic permeability variations may produce similar indications which are not relevant.

(b) Any indication that is believed to be nonrelevant should be reexamined by the same or other NDE methods to verify whether or not actual defects are present. Surface conditioning may precede the reexamination. After an indication has been verified to be nonrelevant, it is not necessary to reinvestigate repetitive nonrelevant indications of the same type. Nonrelevant indications that would mask defects are unacceptable.

(c) Relevant indications are indications which result from imperfections. Linear indications are indications in which the length is more than three times the width. Rounded indications are indications which are circular or elliptical with the length equal to or less than three times the width.

NB-5341 Evaluation of Indications

NB-5342 Acceptance Standards

(a) Only imperfections producing indications with major dimensions greater than 1/16 in. (1.5 mm) should be considered relevant imperfections.

(b) Imperfections producing the following indications are unacceptable:

(1) any cracks and linear indications

(2) rounded indications with dimensions greater than 3/16 in. (5 mm)

(3) four or more rounded indications in a line separated by 1/16 in. (1.5 mm) or less edge to edge

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(4) 10 or more rounded indications in any 6 in.2 (4 000 mm2) of surface with the major dimension of this area not to exceed 6 in. (150 mm) with the area taken in the most unfavorable location relative to the indications being evaluated

NB-5350 LIQUID PENETRANT ACCEPTANCE STANDARDS

NB-5351 Evaluation of Indications (a) Mechanical discontinuities at the surface are revealed by bleeding out of the penetrant; however, localized surface discontinuities, such as may occur from machining marks, surface conditions, or an incomplete bond between base metal and cladding, may produce similar indications which are nonrelevant.

(b) Any indication which is believed to be nonrelevant should be reexamined to verify whether or not actual defects are present. Surface conditioning may precede the reexamination. Nonrelevant indications and broad areas of pigmentation which would mask defects are unacceptable.

(c) Relevant indications are indications which result from imperfections. Linear indications are indications in which the length is more than three times the width. Rounded indications are indications which are circular or elliptical with the length equal to or less than three times the width.

NB-5352 Acceptance Standards

(a) Only imperfections producing indications with major dimensions greater than 1/16 in. (1.5 mm) should be considered relevant imperfections.

(b) Imperfections producing the following indications are unacceptable:

(1) any cracks or linear indications;

(2) rounded indications with dimensions greater than 3/16 in. (5 mm)

(3) four or more rounded indications in a line separated by 1/16 in. (1.5 mm) or less edge to edge

(4) ten or more rounded indications in any 6 in.2 (4000 mm2) of surface with the major dimension of this area not to exceed 6 in. (150 mm) with the area taken in the most unfavorable location relative to the indications being evaluated

ASME Section XI, IWA-2200 (a), states, “A surface examination indicates the presence of surface discontinuities. It may be conducted using a magnetic particle, liquid penetrant, eddy current, or ultrasonic method.” Additionally, ASME Section XI, IWA-9000, defines a surface flaw: a flaw that either penetrates the surface or is less than a given distance from the surface.” Further, Section XI, IWA-2300, Volumetric Examination, states, “A volumetric examination indicates the presence of discontinuities throughout the volume of material and may be conducted from either the inside or outside surface of a component.” The radiographic examination is considered a volumetric method.

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According to ASME Section XI, when a flaw is detected by the magnetic particle, liquid penetrant, or radiographic examination method, it is evaluated as a linear flaw. This is done regardless of the shape of the indication. According to IWA-9000, linear flaw is defined as “a flaw having finite length and narrow uniform width and depth with examples illustrated in Fig. IWA-3400-1, Linear Surface Flaws.” According to Code Interpretation XI-1-86-52, these indications are assumed to be linear regardless of the surface length-to-width ratio—for example 3:1. For example, a rounded indication detected during a liquid penetrant examination would be evaluated as a linear indication by applying its largest or most detrimental dimension to the acceptance criteria. This is different from how ASME Section III defines a linear indication, which states, “Linear indications are indications in which the length is more than three times the width. Rounded indications are indications which are circular or elliptical with the length equal to or less than three times the width.”

ASME Section XI, IWA-2200 (a), states, “A surface examination indicates the presence of surface discontinuities. It may be conducted using a magnetic particle, liquid penetrant, eddy current, or ultrasonic method.” Additionally, ASME Section XI, IWA-9000, defines a “surface flaw: a flaw that either penetrates the surface or is less than a given distance from the surface.” Further, Section XI, IWA-2300, Volumetric Examination, states, “A volumetric examination indicates the presence of discontinuities throughout the volume of material and may be conducted from either the inside or outside surface of a component.” The radiographic examination is considered a volumetric method.

According to Section XI, for a single flaw, the acceptance criteria is based solely on the length () of the flaw. There are two types of defined single flaws, linear and curvilinear, as illustrated in Figure 4-1.

Figure 4-1 ASME Section XI, single flaws

When multiple flaws are detected, their proximity to each other (S) and their relative orientation become additional factors. There are six types of multiple linear flaws: aligned linear, nonaligned parallel, overlapping parallel, overlapping, non-overlapping, and multiple parallel, as illustrated in Figures 4-2 through 4-7.

Figure 4-2 ASME Section XI, aligned linear flaws—1 > 2 (1 is greater than or equal to 2)

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Figure 4-3 ASME Section XI, nonaligned parallel flaws—1 > 2, s is less than or equal to 1

Figure 4-4 ASME Section XI, overlapping parallel flaws

Figure 4-5 ASME Section XI, overlapping flaws

Figure 4-6 ASME Section XI, non-overlapping flaws—1 > 2

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Figure 4-7 ASME Section XI, multiple parallel flaws

Although these criteria may appear complicated, they can be generalized. Figure 4-8 summarizes the proximity requirements (S) for a flaw to be classified as a single linear flaw.

Figure 4-8 Summary of ASME Section XI, linear flaw proximity requirements

If a shorter adjacent flaw comes within this proximity, it must be included in the overall length measurement, as previously illustrated. If it is outside this boundary, as illustrated previously, it does not need to be included as a multiple flaw. For this reason, the rules of proximity should always be applied first and the evaluation process should always start with the largest flaw ().

The acceptance criteria for linear surface flaws detected by liquid penetrant testing, magnetic particle testing, or radiographic testing is based on length expressed as either a finite value or as a percentage of wall thickness. Two typical ASME Section XI, Subsection IWB, allowable linear flaw tables for ferritic and austenitic stainless steel, Table IWB-3510-3 and Table IWB-3518-2, are shown in Figures 4-9 and 4-10, respectively.

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Figure 4-9 ASME Section XI, Table IWB-3510-3

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Figure 4-10 ASME Section XI, Table IWB-3518-2

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The acceptance criteria for laminar flaws is based on area. Figure 4-11 shows a typical table.

Figure 4-11 ASME Section XI, Table IWB-3510-2

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Section 5: Process for Interpretation of Radiographic Indications

Introduction

The art and science of the interpretation and analysis of radiographic images is a complex task that requires a thorough understanding of the principles of industrial radiography, including the basic geometry of image formation, standard radiographic techniques, isotopic and electronic radiographic sources, material product forms and properties, potential discontinuity types and characteristics, analog and digital recording media, and applicable codes and standards.

The interpretation of radiographic images is not a precise science. Qualified interpreters with many years of experience will often disagree on the nature of discontinuities and their disposition. The information contained in this section will assist the interpreter with the task of evaluating radiographic images of critical safety-related nuclear components.

Background

Radiographic interpretation is considered to be a three-step process that consists of detection, interpretation, and evaluation of images. Central to this process is the interpreter’s visual acuity and the conditions under which the radiographic images are viewed [13]. The images for analog and digital recording media should be viewed under subdued background lighting of an intensity that will not cause reflections, shadows, or glare on the image media—that is, radiographic film or digital monitor display. Equipment used to view radiographic images for interpretation should provide a light source or monitor intensity sufficient for the penetrameter and the essential penetrameter hole to be visible for the specified density or pixel value. The viewing conditions should be so that light from around the outer edges of the radiographic image or coming through low density or lighter portions of the image does not interfere with interpretation [14]. The brightness of the surrounding room should be about the same as the brightness of the area of interest in the image [13]. A short period, approximately 5–10 minutes or that specified in an applicable code, specification, or procedure, of dark adaption for the interpreter is recommended prior to beginning the process of interpretation to allow the eyes to adjust to the subdued lighting.

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Analog Images

Image Quality

The radiographic interpreter must first accept the quality of the image by evaluating the film for handling and processing effects that can lead to artifacts, or false indications.

All radiographs should be free from mechanical, chemical, or other blemishes to the extent that they do not mask or be confused with the image of any discontinuity in the area of interest in the radiograph [5].Typical film artifacts that lead to unsatisfactory images are detailed below.

There any many causes for unsatisfactory radiographic film images; these can usually be traced to poor film handling and housekeeping, as well as improper development. The most effective and simplest way to identify and eliminate most film artifacts is the use of the double film technique, which allows comparison of the two films loaded and exposed together in a cassette. Film artifacts can occur before, during, or after processing. Film artifacts occurring during processing can be further classified as being a result of manual or automated processing.

Conditions that may lead to film artifacts before processing include the following:

Film scratches

Pressure marks

Crimp marks

Static charge marks

Screen marks and blemishes

Fog

Light exposure

Fingerprints

False indications from defective intensifying screens

Conditions that may lead to film artifacts during processing include the following:

Underdevelopment/overdevelopment

Chemical streaks (manual)

Spotting (manual)

Yellow stains

Reticulation

Frilling

Air bells or bubbles

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Dirt/dust

Pi lines (automated)

Pressure marks (automated)

Kissing (manual)

Delay streaks (automated)

Conditions that may lead to film artifacts after processing include the following:

Scratches

Fingerprints

Yellowing resulting from aging and improper washing/fixing during processing

Adhesive transfer and acid from storage envelopes [13]

Radiographic Density

Density Limitations

The transmitted film density through the radiographic image of the body of the appropriate hole image quality indicator (IQI) or adjacent to the designated wire of a wire IQI and the area of interest should be 1.8 minimum for single film viewing for radiographs made with an X-ray source and 2.0 minimum for radiographs made with a gamma ray source. For composite viewing of multiple film exposures—that is, the double film technique—each film of the composite set should have a minimum density of 1.3. The maximum density should be 4.0 for either single or composite viewing. A tolerance of 0.05 in density is allowed for variations between densitometer readings.

Density Variation

General

If the density of the radiograph anywhere through the area of interest varies by more than minus 15% or plus 30% from the density through the body of the hole penetrameter or adjacent to the designated wire of a wire IQI, within the minimum/maximum allowable density ranges, an additional IQI should be used for each exceptional area or areas and the radiograph retaken. When calculating the allowable variation in density, the calculation can be rounded to the nearest 0.01 within the minus 15% to plus 30% range. When shims are used with hole-type IQIs, the plus 30% restriction can be exceeded and the minimum density requirements do not apply for the IQI, provided that the required sensitivity is met.

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Image Quality Indicators

Required Sensitivity

Radiography should be performed with a technique of sufficient sensitivity to display the designated hole IQI image and the essential hole or the essential wire of a wire IQI. The radiographs should also display the IQI identifying numbers and letters. If the designated hole IQI image and essential hole, or essential wire, do not show on any film in a multiple film technique but do show in composite film viewing, interpretation should be permitted only by composite film viewing.

Equivalent Hole-Type Sensitivity

A thinner or thicker hole-type IQI than the required IQI may be substituted, provided that an equivalent or better IQI sensitivity, as listed in ASME Section V, Article 2, Table T-283 (see Figure 5-1), is achieved and all other requirements for radiography are met. Equivalent IQI sensitivity is shown in any row of Table T-283 that contains the required IQI and hole. Better IQI sensitivity is shown in any row of Table T-283 that is above the equivalent sensitivity row. If the required IQI and hole are not represented in the table, the next thinner IQI row from Table T-283 can be used to establish equivalent IQI sensitivity.

Figure 5-1 ASME Section V, Article 2, Table T-283

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Excessive Backscatter

ASME Section V, Article 2, requires control of backscattered radiation from floors or other surrounding objects that might degrade the radiographic image quality. It requires the placing of a lead letter B on the back of the radiographic film cassette. If a light image of the B appears on a darker background of the radiograph, protection from backscatter is insufficient and the radiograph should be considered unacceptable. A dark image of the B on a lighter background is not cause for rejection.

ASME Radiographic Evaluation

Prior to being presented to the authorized nuclear in-service inspector (ANII), the images should be examined and evaluated by the manufacturer as complying with ASME Section V, Article 2, and ASME Section XI. The radiographic images should be accompanied by a completed radiograph review form, including the radiographic technique information and indication dispositions, when presented to the ANII for acceptance.

The manufacturer should be responsible for the review, interpretation, evaluation, and acceptance of the completed radiographs to ensure compliance with the requirements of ASME Section V, Article 2, and the referencing Code section. As an aid to the review and evaluation, the radiographic technique documentation required by ASME Section V, Article 2, paragraph T-291, should be completed prior to the evaluation. The radiograph review form required by ASME Section V, Article 2, paragraph T-292, should also be completed during the evaluation. The radiographic technique details and the radiograph review form should accompany the radiographs. Acceptance should be completed prior to the presentation of the radiographs and accompanying documentation to the ANII.

Documentation

Radiographic Technique

After determining that the image quality, density, and sensitivity are acceptable, the radiographic interpreter should begin the detection process with a review of the radiography technique documentation provided by the radiographer with the film or digital images. This reader sheet should provide the interpreter with detailed accurate information of the radiographic technique used for an image or series of images prior to beginning the interpretation process. This will allow the interpreter to verify and judge the adequacy and applicability of the radiographic technique required by the controlling Code or specification.

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As a minimum, ASME Section V, Article 2, requires documentation of the following:

Manufacturer’s name and permanent identification on the image traceable to the part or component (T-224)

Dimensional map of marker placement (if used in place of location markers [T-275.3])

Number of images or exposures

X-ray voltage or isotope used

Source size (F in T-274.1)

Base material/weld type and thickness, including reinforcement thickness, if applicable

Source-to-object thickness (D in T-274.1)

Distance from source side of object to recording medium (d in T.274.1)

Film/type/designation

Number of films in each cassette

Single- or double-wall exposure

Single- or double-wall viewing

In addition to the minimum Code requirements, other items are typically included in the radiographic technique documentation. They are as follows:

Type of intensifying screens used, if any

Governing Code or specification and acceptance criteria

X-ray milliampere or source curie strength

Procedure and revision number

IQI type, size, location (source or film side), required sensitivity, and shim thickness, if used

Sketch of the radiographic setup

Radiation beam filters, if used

Backscatter protection/masking or blocking

Geometric unsharpness

Exposure time

Film processing information (manual or automated)

Image plate (computed radiography) processing information

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The radiographic technique documentation is required to be included on the radiographic review form that is completed by the interpreter during the evaluation process. As a minimum, the radiographic review form should include the following:

Radiographic technique documentation

Listing of each exposure image location

Evaluation and disposition of the materials or welds examined

Name of interpreter

Date of the evaluation

Radiograph Review Form

The radiographic technique documentation is required to be included on the radiograph review form that is completed by the interpreter during the evaluation process. As a minimum, the radiograph review form should include the following:

Listing of each exposure image location

Radiographic technique documentation (T-291)

Evaluation and disposition of the materials or welds examined

Name of the manufacturer’s representative who performed the final acceptance of the radiographs

Date of manufacturer’s evaluation

The radiograph review form should also include other information, as follows, that may be important for secondary evaluations and subsequent engineering evaluation and disposition of any unacceptable discontinuities:

Examination limitations/coverage

Certification level of the interpreter

Comments by the interpreter

Precise flaw measurements (lengths and endpoints) and distance from permanent location markers

Indication numbering to maintain traceability, if multiple indications are in the area of interest

Artifacts/processing defects

Repairs, if any (typically denoted by an R preceding the exposure number) [5]

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Film Interpretation Considerations

Experience is the key to successful film interpretation. The experienced film interpreter will develop a personal step-by-step process to assess radiographic technique variations that can affect interpretation and evaluation. One of the most important things an interpreter can do to detect technique errors is to obtain a detailed scale drawing of the component or weld. Knowledge of the weld joint design, material types and thicknesses, and welding process(es) and their associated discontinuities is essential to making an accurate interpretation of the radiographic images.

The film interpreter should also have the necessary equipment and tools within reach. A partial list of desirable equipment includes the following:

High-intensity, variable-intensity illuminator, with foot pedal control; spare bulbs and sufficient illuminator viewing masks

Calibrated densitometer, with aperture set

Magnifier, 5–10x

Comparator, with etched glass scale [13]

Clear ruler, with standard and metric scales

Grease pencils

Clear plastic overlays

Film storage leaves and jackets

Cotton gloves

Report forms

Digital Images

For a number of years, computer digitization of radiographic film has become a recognized practice for the enhancement of images and/or storage of the images. As improvements in computer digitization technology have increased, digitization of radiographs has become a more common practice and requires appropriate process controls to ensure that the Code requirements are maintained. Additionally, newer technology allows the direct capture of radiographic images on digital media. These digital media include phosphor plates or digital detectors. As with all technology, there are advantages and limitations to these radiographic imaging techniques. The industry codes and specifications are being developed to ensure that the necessary requirements are being addressed [13].

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Evaluation of Digitized Film Images—ASME Section V, Article 2, Mandatory Appendix VI

General Requirements

Digital Image Viewing Considerations

The digital image should be judged by visual comparison to be equivalent to the image quality of the original image at the time of digitization.

Evaluation

Process Evaluation

The radiographic Level II or Level III examiner described in VI-223(a) should be responsible for determining that the digital imaging process is capable of reproducing the original analog image. This digital image should then be transferred to the write-once-read-many (WORM) optical disc. The examiner must use the digitized representation of the reference targets (reference film) to assess system performance as described in VI-240 and VI-250. The reference film should be used to conduct performance demonstrations and evaluation of the digitizing system to verify the operating characteristics before radiographs are digitized (VI-A-210).

Interpretation

When interpretation of the radiograph is used for acceptance, the requirements of Article 2, Mandatory Appendix IV, and the referencing Code section should apply. If analog radiographs must be viewed in composite for acceptance, both radiographs should be digitized. The digital image of the analog radiographs should be viewed singularly.

Appendix IV contains the evaluation requirements for interpretation in Section IV-280.

Factors Affecting System Performance

The quality of system performance is determined by the combined performance of the components specified in IV-258. These are as follows:

Digital image acquisition system

Display system

Image processing system

Image storage system

System-Induced Artifacts

The digital system should be free of system-induced artifacts in the area of interest that could mask or be confused with the image of any discontinuity.

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Digital Imaging Technique Information

To aid in proper interpretation of the digital examination data, details of the technique used should accompany the data. As a minimum, the information should include items specified in T-291 and II-221, III-221, IV-221, IV-222, and the following:

Operator identification

System performance test data

Calibration test data

Evaluation by Manufacturer

Prior to being presented to the inspector for acceptance, the digital examination data from a radiographic or radioscopic image should have been interpreted by the manufacturer as complying with the referencing Code section. The digitized examination data that have previously been accepted by the inspector are not required to be submitted to the inspector for acceptance.

Baseline

Digital images of previously accepted radiographs can be used as a baseline for subsequent ISIs.

Documentation

Reporting Requirements

The following should be documented in a final report:

Spatial resolution (VI-241)

Contrast sensitivity (VI-242)

Frequency for system verification

Dynamic range (VI-243)

Traceability technique from original component to radiograph to displayed digital image, including original radiographic reports (The original radiographic reader sheet may be digitized to fulfill this requirement.)

Condition of original radiographs (VI-281)

Procedure demonstration (VI-261)

Spatial linearity (VI-244)

System performance parameters (VI-241)

Personnel performing the digital imaging process (VI-223)

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Archiving

When the final report and digitized information are used to replace the analog radiograph as the permanent record as required by the referencing Code section, all information pertaining to the original radiography should be documented in the final report and processed as part of the digital record. A duplicate copy of the WORM storage media is required if the radiographs are to be destroyed.

Evaluation of Phosphor Imaging Plate Images—Article 2, Mandatory Appendix VIII

General Considerations

Facilities for Viewing of Radiographs

Viewing facilities should provide subdued background lighting of an intensity that will not cause reflections, shadows, or glare on the monitor that interferes with the interpretation process.

Evaluation

System Induced Artifacts

The digital image should be free of system-induced artifacts in the area of interest that could mask or be confused with the image of any discontinuity.

Image Brightness

The image brightness through the body of the hole-type IQI or adjacent to the designated wire of the wire-type IQI, should be judged to be equal to or greater than the image brightness in the area of interest for a negative image format. This image brightness requirement is reversed for a positive image format. Additionally, the requirements of T-282 are not applicable to phosphor imaging plate radiography.

Required IQI Sensitivity

Radiography should be performed with a technique of sufficient sensitivity to display the designated hole-type image and the essential hole, or the essential wire of a wire-type IQI. The radiograph should also display the IQI identifying numbers and letters. Multiple film technique is not applicable to phosphor imaging plate radiography.

Sensitivity Range

The contrast and brightness range that demonstrates the required sensitivity should be considered valid contrast and brightness values for interpretation. When multiple IQIs are used to cover different thickness ranges, the contrast and brightness range that demonstrates the required IQI image of each IQI should be determined. Intervening thicknesses can be interpreted using the overlapping portions of the determined contrast and brightness ranges. When there is no overlap, an additional IQI(s) should be used.

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Measuring Scale

The measuring scale that is used for interpretation should be capable of providing dimensions of the projected image. The measurement scale tool should be based upon a known dimensional comparator that is placed on the cassette.

Interpretation

Final radiographic interpretation of the area of interest should be performed with the identified IQI image contrast and brightness or, if multiple IQIs are used, the overlapping portions of the identified contrast and brightness values for the intervening thickness ranges as determined according to VII-283.3. The IQI and the area of interest should be of the same image format (positive or negative). Additionally, where applicable, visual comparators, such as film strips and gray-scale cards, can be used to aid in judging displayed image brightness. When comparators are used to judge areas within the image, they need not be calibrated, the digital image can be viewed and evaluated in a positive or negative image format, and independent areas of interest of the same image can be displayed and evaluated in differing image formats, provided that the IQI and the area of interest are viewed and evaluated in the same image format.

Documentation

Digital Imaging Technique Documentation Details

The manufacturer should prepare and document the radiographic technique details. As a minimum, the following information should be provided:

Identification as required by T-224

The dimensional map of marker placement (if used in place of location markers) in accordance with T-275.3

Number of exposures

X-ray voltage or isotope used

Source size (F in T-274.1)

Base material/weld type and thickness, including reinforcement thickness, if applicable

Source-to-object thickness (D in T-274.1)

Distance from source side of object to recording medium (d in T.274.1)

Storage phosphor manufacturer and designation

Image acquisition (digitizing) equipment manufacturer, model, and serial number

Single- or double-wall exposure

Single- or double-wall viewing

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Procedure identification and revision level

Imaging software version and revision

Numerical values of the final imaging processing parameters—that is, filters, window (contrast), and level (brightness) for each view.

The technique details can be embedded in the data file. ASTM E- 1475 can be used as a guide for establishing data fields and information content [5].

Digital Image Processing

Introduction

Most of the raw digital images acquired by the preceding techniques are gray-scale images that are not very useful without some sort of image processing. Digital processing can be defined as any digital operation performed on a digital image for the purpose of enhancing or improving the visibility of desired image features. Digital image processing can have a profound effect on the end results of image interpretation, so a good understanding of the fundamental concepts of digital processing is essential to the evaluation of digitized images. The commercial hardware and software that are available with these systems typically perform the same signal processing operations, but the processing operations may have different names and software protocols. The digital image interpreter should not only be familiar with the basic fundamentals of image processing but also be aware of manufacturer variations in software [15]. Digital enhancement is accomplished through the use of computer algorithms that make changes to the original gray-scale matrix. The computer software knows the gray-scale value of each pixel on the display monitor. Any number of instructions can be generated by the computer to reassign any number or combination of gray-scale values. There are often limits to the amount of processing that can be done before the results degrade the image rather than enhance it. In some instances of overdriving, a feature can be processed beyond the capability of the electronic display to accurately display the image. These practices can lead to image distortion, such as aliasing or blooming [16].

Contrast and Brightness

Contrast (window) and brightness (level) are the most commonly used image processing tools. All systems offer the ability to adjust the window/level. Window is the common term for the relationship of the light and dark areas in the image, and level determines how light or dark the overall image appears. These adjustments are accomplished through the use of look-up tables where the pixel values are reassigned from a reference table to lighter or darker values. Many systems allow adjustments of these values simultaneously. The interpreter must be careful not to adjust these values past the minimum pixel value from the original image where the image deteriorates and information may be lost. Window and leveling processing can also allow image reversal to positive for enhanced interpretation. Knowledge and experience with the individual software is essential to their effective use [17].

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Histogram Analysis

A histogram is a compilation of all pixel values within the total image categorized by each pixels gray-scale value. The main idea of a histogram is to allow the interpreter to identify areas within the image that might not be needed for evaluation of the image or to change pixel contrast/brightness (window/level) in selected areas of the histogram. This process allows other processing techniques to be more easily applied to selected areas of interest. Histogram equalization is most useful for images without a wide range of contrast, such as when a part or component with low subject contrast entirely covers the detector. The histogram is useful in determining proper exposure. A 12-bit full digital image pixel histogram has pixel values from 0 to 4096 on the horizontal axis of the histogram. Acceptable images can be achieved when the primary image data are located within 1/4 (1024) to 3/4 (3072) of the horizontal scale. If the histogram is too far to the left, the image is underexposed. If the histogram is too far to the right, the image is overexposed.

Filters

Digital filters apply algorithms that selectively reassign original pixel values to enhance the visibility of a selected feature and suppress noise from surrounding pixels. Pixels can be divided into three categories: resident pixels (darkest), neighboring pixels (lighter), and neighborhood pixels (lightest). Resident pixels are completely within the boundaries of the selected feature, neighboring pixels are adjacent to the feature, but not completely within or outside of the feature, and neighborhood pixels are the other lighter pixels around the feature that provide enough contrast for the feature to be seen. Most filtering operations involve the neighboring pixels [16].

Filtering does not always enhance a selected feature (such as the essential hole or wire of an IQI) and it can be overapplied to the point where the image is distorted. Noise reduction filters are linear filters that add, subtract, multiply, divide, or average the individual pixel values in a 3 x 3 pixel group and replace the center pixel with the result. These include smoothing and median filters. High-pass filters serve to sharpen features in the image by increasing the target feature (center) pixel value and greatly lowering (subtracting) the surrounding pixel values to a negative value; overall image quality must be maintained by lowering the surrounding pixels by the same value. Low-pass filters blur the image by increasing the target feature pixel value and slightly lowering the surrounding pixel values. Edge enhancement filters accentuate linear patterns in the image by greatly lowering the target feature pixel value to a negative number and increasing the surrounding pixel values to a positive number. Embossing filters offer a unique presentation of the image where any significant thickness change is highlighted by providing a relief of the image [15].

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Magnification

Image enlargement can be a valuable tool for the interpreter. The image is digitally enlarged on the display monitor. Enlargement more than four times the original pixel size can cause distorted images. The original pixel density must be preserved in the magnified image. Magnification is also limited by the capability of the monitor to display the enlargement [17].

Digital Image Interpretation

Dimensional Measurements

Dimensional measurement software requires calibration of the measurement tool by including a part of known dimensions in the radiograph (round sphere, step wedge, or IQI) and displaying this image on the monitor. Care should be taken not to enlarge the feature to be measured. Measurement of a feature directly on the monitor with a ruler is not recommended [16].

Discontinuity Indications

After determining the acceptability of the film/phosphor imaging plate/digital detector technique and the image quality, the radiographic interpreter must determine the type and the disposition of any indications noted in the area of interest and record these on the radiographic report. The radiographic report should contain a list of potential discontinuities found in the material under examination and detectable by the radiographic method for the interpreter to reference [14]. Article 1, Nonmandatory Appendix A, Table A-110 contains a summary of service-induced imperfections, welding imperfections, and product form imperfections that are considered to be detectable by radiographic examination [5]. Many radiographic publications contain excellent radiographic reproductions of typical discontinuities combined with photomicrographs of the discontinuity that can be used as a reference for radiographic interpretation [12].

ASME Section XI Acceptance Criteria

After an indication is detected by radiographic testing and determined to be a flaw, the length (size) must be measured at the greatest dimension of the flaw, including any enlargement due to radiographic technique, and rounded in accordance with IWA-3200. ASME Section XI defines flaws found with radiographic testing as linear surface flaws. The flaw size is then compared with Section XI requirements for that particular component found in the appropriate subsection (IWB, Class I; IWC, Class 2, and so forth), article (3000, Acceptance Standards), and examination category (B-A, B-G-1, and so forth). The acceptance criteria for linear surface flaws are based on flaw length and part thickness, as well as proximity to other flaws. See Section 4 of this report for additional details [18].

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Section 6: Process for Interpretation of Magnetic Particle Indications

There are three fundamental elements in any NDE method. These elements are the following:

Production of an indication (In the magnetic particle method, this is an indication on the surface of the part.)

Interpretation of the indication as to what condition(s) of the part caused it

Evaluation of the condition(s) as to the effect and extent that it will affect the part usability

Production of meaningful magnetic particle indications is dependent on the proper technique selection for the part to be examined, as well as the proper application of the technique. Knowledgeable and experienced magnetic particle Level III personnel should select the technique(s) required to provide the best possible capability for the detection of relevant discontinuities. The technique(s) selected should obviously meet the minimum required Code or specification requirements for the part. Additionally, the magnetic particle Level III personnel should ensure that a qualified procedure has been developed and demonstrated to ensure that the technique(s) to be used is capable of detecting the required discontinuities.

ASME Section XI references ASME Section V, Nondestructive Examination, for the requirements to perform NDE examinations. ASME Section V, Appendix I—Glossary of Terms for Nondestructive Examination, defines procedure demonstration: when a written procedure is demonstrated, to the satisfaction of the inspector, by applying the examination method using the employer’s written NDE procedure to display compliance with the requirements of this section, under normal examination conditions according to T-150(a) or special conditions as described in T-150(b) Additionally, it defines procedure qualification: when a written NDE procedure is qualified in accordance with the detailed requirements of the referencing Code Section [5],

Parts on which no indication appears can be presumed free of discontinuities and can be considered acceptable for use. Parts on which indications appear require further consideration to determine their condition.

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The next element is the interpretation of the indication. The indication of the presence of a discontinuity by a magnetic particle examination is, literally, just that. It is an indicator that something in the part is not normal. However, it does not, by itself, reveal exactly what the discontinuity is that produced it. In magnetic particle examination, every indication pattern is produced by a magnetic disturbance that results in a leakage field. Additional knowledge and information are required to determine whether the indication pattern and the magnetic disturbance are truly significant. This requires a knowledgeable and experienced magnetic particle examiner to interpret the indication based on the cause.

To reiterate the concepts addressed in Section 3 of this report, Figure 6-1 illustrates the process for the determination as to whether the indication is false, relevant, or nonrelevant. It might be instructive to review the following while considering Figure 6-1:

A false indication is an NDE indication that is interpreted to be caused by a condition other than a discontinuity or imperfection [5]. False indications that result when performing magnetic particle examination are indications that result from some condition other than a magnetic flux field, such as where dry magnetic particles are held mechanically or by gravity in surface irregularities. Improper cleaning or material getting on a surface after cleaning, such as grease or oil, can also result in false indications. For wet magnetic particles, false indications can result from drainage lines on the part surface.

A relevant or nonrelevant magnetic particle indication is one that results from a magnetic flux field from a discontinuity in the part. Nonrelevant magnetic particle indications are the result of magnetic or metallic discontinuities that are present by design or by conditions that have no effect on the strength or service usefulness of the part. Some examples of discontinuities producing nonrelevant magnetic particle indications are a press- or shrink-fit between two parts of a component; a weld joint between two ferromagnetic materials with different magnetic permeabilities or a weld joint between a ferromagnetic and nonferromagnetic material; and segregation of base metal constituents.

Another example of a nonrelevant magnetic particle indication is called magnetic writing. These indications can result during part handling where a magnetized part comes in contact with a nonmagnetized one. This contact can produce localized magnetized areas that will attract and hold magnetic particles. The appearance of these indications is not distinct, such as those typically from surface flaws—for example, cracks and bursts. The magnetic particle examiner is cautioned against misconstruing such indications as being caused by subsurface discontinuities. Whether an indication is caused by magnetic writing or by a subsurface discontinuity can be determined by demagnetizing and reprocessing the part. Demagnetizing will remove the magnetic writing. If the indication returns after demagnetizing and reprocessing, it is an indication of a discontinuity at or near the surface.

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– Relevant magnetic particle indications occur when a magnetic flux field occurs in response to a flaw. Magnetic particle indications from a crack in a weld, a burst in a forging, or a seam or lamination in a rolled plate are examples of relevant indications. An indication from a service-induced mechanical fatigue crack is also a relevant indication. Note: The term flaw is defined as an imperfection that may be detectable by nondestructive testing and is not necessarily rejectable [5].

Relevant indications require characterization and evaluation.

– Flaw characterization is the process of quantifying the size, shape, orientation, location, growth, or other properties, of a flaw based on its NDE response [7].

– Evaluation is a review, following interpretation and characterization of the indication, to determine whether the discontinuity meets specified acceptance criteria [7].

Figure 6-1 Fundamental NDE evaluation process

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For an NDE examiner to make the proper interpretation as to whether an indication is false, nonrelevant, or relevant requires considerable knowledge, skill, and experience. This knowledge includes not only the NDE method that is applied but also detailed information on the component and its potential associated discontinuities. In nearly all instances, an experienced magnetic particle Level II or III examiner can accurately determine from the location and appearance of a magnetic particle indication what has caused the formation of the indication. This can only be done accurately by the examiner knowing the part’s history, including its chemical composition, method of production—that is, wrought, cast, and so forth—and primary and secondary processing.

There are two broad categories of relevant magnetic particle indications. These are indications from surface and subsurface discontinuities. Surface discontinuity indications present as sharp, distinct magnetic particle accumulations, usually tightly held to the part’s surface. Discontinuities, such as surface cracks, rolling, and forging laps, are examples of these tight surface conditions that can be difficult to see with the unaided eye and are typically the more critical type. Subsurface discontinuity indications, on the other hand, typically present as broader, fuzzier magnetic particle accumulation, as compared with those formed by surface discontinuities. The farther below the surface, the broader and less distinct the indications present. It is usually relatively easy for an experienced examiner to determine whether the discontinuity is surface or subsurface, based on the indication appearance. Additionally, by removing the magnetic particle accumulation, the examiner can visually examine the surface directly and often can directly see the discontinuity. A magnifier (3–5x) might be needed to aid in this examination. In the event that there is no surface indication when visually examined, the indication is most likely from a completely subsurface discontinuity. Additional information can also be gained by removing the magnetic particle indication and reapplying the magnetic particles to determine whether the indication reappears. Depending on the material’s magnetic properties and the discontinuity characteristics, the residual magnetism can result in the indication reformation. Obviously, this will be less sensitive than the continuous method; however, it can provide the magnetic particle examiner additional information about the nature of the discontinuity.

After an indication is interpreted and determined to be a relevant indication, it must be characterized. Determining the flaw characteristics from the NDE data and knowledge of the material and processes that caused it is essential to proper evaluation. Evaluation determines whether the flaw is acceptable in accordance with the applicable Code or specification acceptance criteria. For example, in most construction codes applicable to welds, cracks, lack of fusion, and lack of penetration are unacceptable regardless of other characteristics, such as size, shape, orientation, and location. Other relevant indications, such as porosity, slag, and tungsten inclusions, can be acceptable, based on their characteristics. Appendix B provides examples of how two utilities address detected indications.

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All NDE methods produce indirect indications of discontinuities. However, the indications do not directly reveal what the discontinuities are. The indications must be correctly interpreted before they provide the information as to the actual condition of the material. For example, a broad fuzzy linear magnetic particle indication at the toe of a vee-groove weld is meaningless until a knowledgeable, experienced magnetic particle examiner interprets the indication.

Magnetic particle examination produces indications on the surface of materials that are rather clearly related to the size and shape of the discontinuity causing the indication. In fact, in some cases when the discontinuity is at the surface, it can be directly seen after it is detected by the magnetic particle. Of course, subsurface discontinuities cannot be visually detected, but they can provide valuable information as to the nature of the discontinuity. Regardless, the indicaton still has to be interpreted to determine what type of discontinuity it is and characterized to assess its impact on the component usefullness.

In general, interpretation of an NDE indication means to make a decision as to what is the cause of the indication. As addressed in the glossary in Section 1, ASME Section XI defines interpretation as the determination of whether indications are relevant or nonrelevant. ASME Section XI, unlike many other codes and specifications, does not require the examiner to determine the type of discontinuity detected, —that is, it does not require the distinction between crack, lack of fusion, cold shut, and so forth to evaluate the flaw to the acceptance criteria. For plant modifications and R/R activities, however, the construction Code requirements apply. As shown below, from ASME Section III, Rules for Construction of Nuclear Plant Facilities, Division 1, Subsection NB, Class 1 Components, the examiner does have to characterize discontinuity indications to evaluate them to the acceptance standards. Are, for example, magnetic particle and liquid penetrant indications, according to ASME Section III, “any cracks and linear indications”? Based on these requirements, the examiner must have the knowledge and experience to characterize indications resulting from base material product form discontinuities—that is, castings, forgings, rolled products, extrusions, drawn products, welds made with various welding processes, and in-service discontinuities.

ASME Section V, Nondestructive Examination, paragraph T-777, Interpretation, which is referenced by ASME Section XI, states, “The interpretation should identify if an indication as false, nonrelevant, or relevant. False and nonrelevant indications should be proven as false or nonrelevant. Interpretation should be carried out to identify the locations of indications and the character of the indication.” ASME Section V, paragraph T-780 Evaluation, further requires the following:

(a) All indications should be evaluated in terms of the acceptance standards of the referencing Code Section.

(b) Discontinuities on or near the surface are indicated by retention of the examination medium. However, localized surface irregularities due to machining marks or other surface conditions may produce false indications.

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(c) Broad areas of particle accumulation, which might mask indications from discontinuities, are prohibited, and such areas should be cleaned and reexamined. [5]

Section 4 of this report details the ASME Section XI Code requirements for the evaluation of magnetic particle indications. Refer to it for additional guidance.

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Section 7: Process for Interpretation of Liquid Penetrant Indications

All NDE methods produce indirect indications of discontinuities. However, the indications do not directly reveal what the discontinuities are. The indications must be correctly interpreted before they provide the information as to the actual condition of the material. For example, a radiographic film displaying dark lines, spots, or density variations is meaningless until a knowledgeable, experienced radiographer interprets the indications.

Liquid penetrant examinations methods produce indications on the surface of materials that are rather clearly related to the size and shape of the discontinuity that is open to the surface causing the indication. In fact, in some cases, when the discontinuity is open to the surface, it can be directly seen by visual examination after it is detected by the liquid penetrant method. Regardless, the indicaton still has to be interpreted to determine which type of discontinuity it is and characterized to assess its impact on the component usefullness. Even though the acutal discontinutity can be seen visually, it is the actual penetrant indication’s length and/or width that is measured for evaluation.

As previously addressed, interpretation of an NDE indication means to make a decision as to what is the cause for the indication. As addressed in the glossary in Section 1 of this report, ASME Section XI defines interpretation as the determination of whether indications are relevant or nonrelevant. ASME Section XI, unlike many other codes and specifications, does not require the examiner to determine the type of discontinuity detected—that is, it does not require the distinction between crack, lack of fusion, cold shut, and so forth, to evaluate the flaw to the acceptance criteria. For plant modifications and R/R activities however, the construction Code requirements apply. As addressed in Section 4 of this report, ASME Section III, Rules for Construction of Nuclear Plant Facilities, Division 1, Subsection NB, Class 1 Components, the examiner does have to characterize discontinuity indications to evaluate them to the acceptance standards. For example, for liquid penetrant testing, “any cracks and linear indications” have to be interpreted. Based on these requirements, the examiner must have the knowledge and experience to characterize indications resulting from base material product form discontinuities—that is, castings, forgings, rolled products, extrusions, drawn products, welds made with various welding processes, and in-service discontinuities.

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The experience needed for correct interpretation of liquid penetrant indications requires knowledge of the liquid penetrant method and the specific liquid penetrant technique used to procedure the indications. The examiner must know and be experienced to identify conditions that reveal whether the examination process has been conducted properly. For example, in applying the solvent-removal, visible-dye technique using solvent-based wet developer, there are not false or nonrelevant indications present resulting from improper cleaning. Additionally, the developer has not been applied in too heavy of a thickness as to mask potential indications. In the case of fluorescent water washable penetrant technique, the examiner must be certain that the water wash to remove the excess penetrant has been thorough, so that the indication(s) resulting are true indications of relevant discontinuities. The examiner must also be able to derive all possible significant information from the appearance of the indication(s).

In addition to knowledge and experience of the liquid penetrant processing technique used, the task of interpretation becomes easier and more authoritative if the examiner has intimate knowledge of the part being examined. The examiner should know the part’s material, the process by which it is made, and the various subsequent processes though which it has been though to reach the final configuration. Additionally, the examiner should know the kinds of flaws characteristic of the material and should be aware of what type processing flaws may be introduced. Also, if the part has been in service, the examiner should be very familiar with the types of damage mechanisms that may result from the service conditions and how to recognize them. In other words, the examiner should have enough background knowledge and experiences regarding the given part to know in advance which types of flaws are likely to be present, where they are most likely to occur, and what the appearance of these discontinuity indications will be.

The interpretation of liquid penetrant indications is relatively simple as compared with some other NDE methods—for example, UT or eddy current testing. Because a major limitation of liquid penetrant is that can only detect discontinuities that are open to the surface, any true indication can only result from one of two causes: an actual discontinuity in the material that is open to the surface or penetrant remaining on the surface from a nonrelevant condition, such as poor washing or contamination from some external source—for example, lint.

Liquid penetrant nonrelevant indications are usually relatively easy to recognize because they can be directly related to features of the part—for example, the transition area from the base metal of a pipe to the toe of the circumferential weld in a pipe-to-pipe butt-joint. Depending on the specific configuration, it is often difficult to remove the excess penetrant to clean all the excess penetrant at this transition. These and other surface conditions are a common source of nonrelevant indications. Another common example is where cast materials are used. Sometimes cast materials have rough as-cast surfaces. These hold penetrant that will produce indications upon examination. Like the indication on the base metal-to-weld transition, these indications are not a result of inadequate washing during processing but the inability to produce a clean-washed surface. Nevertheless, the indications can interfere with proper interpretation of the part.

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True liquid penetrant indications typically present in one of two forms: linear indications, which are the result of cracks or other crack-like discontinuities—for example, weld lack of fusion or lack of penetration or forging laps—or regular or spotty indications that are caused by porosity.

Each of these crack-like or porosity-type discontinuities, can vary greatly in actual appearance based on size, shape, and extent.

In addition to the significance of the size, shape, intensity (density and volume of the indication), and amount and speed that it spreads can all provide useful information to the examiner as to the actual nature of the discontinuity. Typically, very fine cracks and very small pores produce a more faint indication than indications from larger ones. The wider and/or deeper the crack or the larger the porosity cavity, the greater the volume of penetrant available to bleed out and to form a larger, brighter, and more rapidly forming indication.

The intensity and the speed at which an indication forms provide some qualitative information as to the size and severity of the subsurface portion of the discontinuity—that is, depth of a crack-like discontinuity or the volume of the pore. In a similar way, the speed with which the indication forms provides qualitative information as to the volume of the discontinuity. Relatively large discontinuities form indications immediately and in some instances may not even require application of the developer to see them. On the other hand, very small, tight or fine discontinuities may require high sensitivity penetrant materials, very long penetrant dwell times, and long developer dwell times to even be detected. In some instances, intergranular stress corrosion cracking or primary water stress corrosion cracking may require these longer times.

One of the most effective ways to gain quality training and experience for the proper interpretation of liquid penetrant indications is to acquire a set of parts containing an array of discontinuities representative of those the examiner will encounter. These can be referred to for training as well as serve as reference standards for on-going comparison when performing examinations. Depending on the liquid penetrant technique(s) being employed and the flaw types, it may be possible to reprocess parts to reproduce indications. Another option is to take photographs of the indications of processed parts and develop a reference library of indications.

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Section 8: Conclusions In recent years, there has been a significant improvement in the ability of UT techniques to detect fabrication and service-induced defects, as a result of technology improvement, stringent qualification, and incorporation of industry operating experiences. Discontinuities not previously detected in preservice inspection or ISI are now being detected and utilities are challenged to disposition them accurately.

The process for fully informed interpretation and evaluation of NDE indications requires knowledgeable and experienced qualified personnel using qualified systems. It also requires extensive knowledge of the weld configuration, materials, fabrication history, inspection history, service history, and many other factors. Industry stakeholders should understand that this process requires time to reach the correct results and that efficient execution of the process requires substantial forethought and advance preparation. This report is intended to help all stakeholders to better understand the systematic steps needed to achieve accurate results. This understanding and proactive detailed contingency planning prior to each outage can facilitate this process and can promote effective communications to stakeholders throughout the evaluation.

The goal of this report is to document the indication interpretation and evaluation process that has evolved through several years of industry experience in examination of DMWs. The industry’s practice of continuous improvement will lead to further refinements of the process. EPRI has several current and future activities to refine and reinforce this information and welcomes industry input.

This report contains no guidance with implementation categories defined in NEI 03-08, Revision 2, Guideline for the Management of Materials Issues. Such recommendations will be considered for future revisions.

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Section 9: References In-Text Citations

1. Cognitive Correlates of Ultrasonic Inspection Performance. EPRI, Palo Alto, CA: 1990. NP-6675.

2. INPO Degraded Reactor Coolant System Piping due to Primary Water Stress Corrosion Cracking (LER 338-12-001 update to OE35634).

3. Nondestructive Evaluation: Guideline for Conducting Ultrasonic Examinations of Dissimilar Metal Welds. EPRI, Palo Alto, CA: 2009. 1018181.

4. NEI 03-08, Revision 2, Guideline for the Management of Materials Issues.

5. 2010 Edition, ASME Section V, Nondestructive Examination.

6. 2010 Edition, ASME Section XI, IWA-900 0 Glossary, also has definitions of applicable terms, and some of these definitions vary slightly from those of ASME Section V. Additionally, 2010 ASME Section XI has some additional relevant terms.

7. ASTM E 1316—96 Standard Terminology for Nondestructive Examinations.

8. ANSI CP-189. ASNT Standard for Qualification and Certification of Nondestructive Testing Personnel (ANSI/ASNT CP-189-1995).

9. H. Thielsch, “When Are Weld Defects Rejectable?” Paper presented at the Second Conference on Significance of Defects, London, England (May 29–30, 1968).

10. Appendix VIII, Supplement 10 and 12 Training. EPRI, Palo Alto, CA: 2010. 1021236.

11. Advanced Nuclear Technology: Reduction of American Society of Mechanical Engineers III Weld Fabrication Repairs—Fitness for Purpose. EPRI, Palo Alto, CA: 2010. 1021181.

12. INPO 06-008, Guidelines for the Conduct of Outages at Nuclear Power Plants, Revision 1, February 2011.

13. Nondestructive Testing Handbook: Radiography and Radiation Testing, Vol. 3: American Society of Nondestructive Testing, Columbus, OH. 1985.

14. Radiography in Modern Industry, Fourth Edition: Eastman Kodak Company, Rochester, NY. 1980.

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15. Digital Imaging Course for Industrial Radiography Using Computed Radiography: Virtual Media Integration Ltd., Pensacola, FL.

16. Annual Book of ASTM Standards: Standard Guide for Computed Radiography, E-2007–10: American Society of Testing and Materials, ASTM International, West Conshohocken, PA. 2010.

17. Digital X-Ray Training, Level III, Modules I–VI, 021-022-588, Revision 1: GE Inspection Technologies, Lewistown, PA. 2005.

18. NDE for Engineers, EPRI TM921 921: Radiographic Testing. EPRI, Palo Alto, CA. 2004.

Bibliography

Betz, Carl E. Principles of Magnetic Particle Testing, First Edition: Magnaflux Corporation, Chicago, IL. 1967.

BWR Vessel and Internals Project, Technical Basis for Revisions to Generic Letter 88-01 Inspection Schedules. Boiling Water Reactor Vessel Internals Project (BWRVIP) document BWRIP-75.

BWRVIP information letter 2007-051. Request for Information on Dissimilar Metal Weld Examinations, January 23, 2007.

BWRVIP information letter 2007-139. Request for Information on Dissimilar Metal Weld Examinations, 2nd Request, May 24, 2007.

BWRVIP information letter 2007-154. Dissimilar Metal Weld Contours. June 7, 2007.

BWRVIP information letter 2007-367. Recommendations Regarding Dissimilar Metal Weld Examinations (including Needed Requirements according to NEI 03-08).

BWRVIP letter 2007-321, “Recent Operating Experience (OE) Regarding Dissimilar Metal Weld Examinations.”

BWRVIP-222: BWR Vessel and Internals Project, Accelerated Inspection Program for BWRVIP-75-A Category C Dissimilar Metal Welds Containing Alloy 182. EPRI, Palo Alto, CA: 2009. 1019055.

Czajkowski, C.J. “Evaluation of the Pilgrim Inconel 182 Cracking.” Technical report, A-3763, Brookhaven National Laboratory, Upton, NY, May 1985. 11973.

Czajkowski, C. J. “Metallurgical Evaluation of a Feedwater Nozzle to Safe-End Weld from River Bend Station Unit 1.” Brookhaven National Laboratory, Upton, NY, August 1995.

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Consumers Power letter to the U.S. Nuclear Regulatory Commission, Docket 50-255, License DPR-20, Palisades Plant, “Pressurizer Safe End Crack, Engineering and Root Cause Evaluation.” October 7, 1993.

Dissimilar Metal Piping Weld Examination—Guidance and Technical Basis for Qualification. EPRI, Palo Alto, CA: 2003. 1008007.

Dissimilar Metal Piping Weld Examination Guidance, Volume 2. EPRI, Palo Alto, CA: 2004. 1009590.

Dissimilar Metal Piping Weld Examination Guidance Volume 3. EPRI, Palo Alto, CA: 2005. 1009961.

Enkvist, J., Edland, A., and Svenson, O. “Operator Performance in Non-Destructive Testing: A Study of Operator Performance in a Performance Test.” Swedish Nuclear Inspectorate, 2000. SKI Report 00:26. ISNN 1 1104-1374, ISNRSKIR-00/26-se.

Effect of Decision Making on Ultrasonic Examination Performance. EPRI, Palo Alto, CA: 1992. TR-100412.

INPO 01-002, Guidelines for the Conduct of Operations at Nuclear Power Stations, May 2001.

Jenssen et al., “Metallographic Examination of Cracks in Nozzle to Safe-End Weld of Alloy 182 in Ringhals 4.” Studsvik Nuclear AB, Studsvik/N (H)-00/99, Sweden: December 2000.

Materials Reliability Program: Development of Probability of Detection Curves for Ultrasonic Examination of Dissimilar Metal Welds (MRP-262, Revision 1). EPRI, Palo Alto, CA: 2009. 1020451.

Materials Reliability Program: Primary System Piping Butt Weld Inspection and Evaluation Guidelines (MRP-139). EPRI, Palo Alto, CA: 2005. 1010087.

McMaster, Robert C., Nondestructive Testing Handbook, Volume II: The American Society for Nondestructive Testing, Inc. 1959.

MRP letter 2007-040, “Lessons Learned from Ultrasonic Examinations of Dissimilar Metal Welds.”

Nondestructive Evaluation: Dissimilar Metal Piping Weld Examination Guidance: Volume 4. EPRI, Palo Alto, CA: 2006. 1013540.

Nondestructive Evaluation: Dissimilar Metal Piping Weld Examination Guidance, Volume 5. EPRI, Palo Alto, CA: 2007. 1015136.

Nondestructive Evaluation: Dissimilar Metal Piping Weld Examination Guidance, Volume 6. EPRI, Palo Alto, CA: 2008. 1016648.

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Nondestructive Evaluation: Dissimilar Metal Weld (DMW) Configuration Database. EPRI, Palo Alto, CA: 2006. 1014504.

Nondestructive Evaluation: Guideline for Conducting Ultrasonic Examinations of Dissimilar Metal Welds. EPRI, Palo Alto, CA: 2008. 1018181.

Nondestructive Evaluation: Inspection & Mitigation of Alloy 82/182 Butt Welds. EPRI, Palo Alto, CA: 2008. 1016658.

Nondestructive Evaluation: Proposed Code Case Criteria for Technical Basis of Weld Overlay Indication Evaluation and Disposition Based on Advanced Technology Assessments. EPRI, Palo Alto, CA: 2009. 1019118.

PDI Generic Procedure for the Ultrasonic Examination of Dissimilar Metal Welds, PDI-UT-10: Revision C. EPRI, Palo Alto, CA: 2006.

PDI Generic Procedure for the Ultrasonic Examination of Overlaid Similar and Dissimilar Metal Welds, PDI-UT-8: Revision F. EPRI, Palo Alto, CA.

PDI Site-Specific Demonstrations: Dissimilar Metal Welds Mockup Criteria, Revision A. EPRI, Palo Alto, CA: 2004. 1009590.

Qualification Requirements for Appendix VIII Piping Examinations Conducted from the Inside Surface, Section XI, Division 1, Code Case N-696. American Society of Mechanical Engineers, New York, 2003.

Qualification Requirements for Dissimilar Metal Piping Welds, Section XI, Division 1, Appendix VIII, Code Case N-695. American Society of Mechanical Engineers, New York, 2003.

Rao. G., et al., “Metallurgical Investigation of Cracking in the Reactor Vessel Alpha Loop Hot Leg Nozzle to Pipe W at the VC Summer Nuclear Generating Station.” Westinghouse Electric Company, Westinghouse Non-Proprietary Class 3, WCAP-15616, Pittsburgh, PA (January 2001).

South Carolina Gas and Electric, “VC Summer Hot Leg Cracking.” Addendum to Presentation by South Carolina Gas and Electric, Orlando, FL (December 2000).

Walker, S., “Workshop on Recent Industry Experience with Inspection of Dissimilar Metal Welds.” EPRI Proceedings, San Antonio, TX: March 1998. GC-110310.

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Appendix A: Example PDI Generic Procedure Evaluation Guidance

PDI Generic Procedure for the Ultrasonic Examination of Dissimilar Metal Welds, PDI-UT-10, Revision E, 2/24/2010, Section 9.0

9.0 INDICATION EVALUATION

General Information

All suspected flaw indications, regardless of amplitude, should be investigated to the extent necessary to provide accurate characterization, identity, and location. Re-evaluations (re-looks) with qualified equipment are acceptable. All suspected flaw indications should be plotted on a cross sectional drawing of the weld. Indication plots should accurately identify the specific origin of the reflector.

Note: When using RL search units it is vital that the examiner be aware of all ultrasonic responses inherent to longitudinal wave search units. Ultrasonic responses from both the direct shear wave and/or mode-converted wave modes may provide a more substantial amplitude response than from the direct longitudinal wave response.

Figure A-1 identifies a typical flow path for evaluation of indications.

Indication Classification

Flaw Indications

All indications produced by reflectors within the volume to be examined, regardless of amplitude, that cannot be clearly attributed to the geometrical or metallurgical properties of the weld configuration should be considered as flaw indications.

Non-relevant indications (Geometric/Metallurgical)

All indications produced by reflectors within the volume to be examined that can be attributed to the geometry of the weld configuration should be considered as non-relevant indications.

Geometric indications may be verified by the use of radiographs, as-built drawings, or any other means available to accurately identify the reflector.

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Indication Discrimination

Flaw Indications

All suspected flaw indications should be investigated and evaluated taking into account the following indication characteristics. These characteristics should not be considered as mandatory criteria for classifying indications as flaws, but are listed as significant points of interest for the examiner to consider during evaluation of suspect areas.

The indication has a good signal-to-noise ratio with defined start and end points. This characteristic can be supported by observing signal-to-noise ratio variation along the length of the component.

The indication plots to a location susceptible to cracking. This characteristic can be supported by obtaining localized thickness and surface contour recordings at the location of the indication(s).

The indication provides substantial and unique echo-dynamic travel (walk). This characteristic can be supported by observing other areas along the weld length and through the use of an adequate reference reflector (Inside surface notch or equivalent).

Several areas of unique amplitude peaks are observed throughout the indication length. This characteristic can be supported by observing other areas along the weld length and by scanning along the indication length laterally.

Inconsistent time base positions are observed throughout the indication length. This characteristic can be supported by scanning along the indication length laterally.

The indication shows evidence of flaw tip signals.

Circumferential indications provide axial components while performing tangential scans.

The indication(s) can be confirmed from the opposite direction. This characteristic is dependent upon flaw orientation and configuration and may not always be available.

The indication(s) can be confirmed with an additional examination angle. This characteristic is dependent upon flaw orientation and configuration and may not always be available.

For components where access is limited to a single side of the component, the following additional information should be considered:

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As a result of the uncertainties associated with sound propagation through austenitic weld material and buttering, actual flaw positioning, and the true thickness of the component, an accurate ID connection on the far side of the weld may be unobtainable.

For suspect far side flaw indications several search unit parameters (e.g., lower frequencies, different angles, different focal depths, etc.) should be evaluated to optimize response.

Non Relevant Indications

All suspected non-relevant indications should be investigated and evaluated taking into account the following indication characteristics. These characteristics should not be considered as mandatory criteria for classifying indications as non-relevant, but are listed as significant points of interest for the examiner to consider during evaluation of suspect areas.

The indication appears at or near the centerline of the weld or other documented geometrical condition and can be seen continuously or intermittently along the length of the weld at consistent amplitude and time base positions. This characteristic can be supported by obtaining localized thickness and surface contour recordings at the location of the indication(s).

The indication provides additional responses, which occur from the same scan position, but at different time base positions (multiples) along the length of the weld. This may be a sign of mode-converted shear-wave signals from counterbore or similar geometric reflectors. This characteristic may require an increase in time base size in order to observe these responses.

The indication can be seen across the entire length of the scan, either continuously or intermittently, at consistent amplitude and time base positions. This characteristic can be supported by scanning along the indication length laterally.

The indication provides minimal echo-dynamic travel (walk). This characteristic can be supported by observing other areas along the length of sample and through the use of an adequate reference reflector (inside surface notch or equivalent).

The signal responses are consistent from each side of the weld for axial scans, or from each direction (cw or ccw) for circumferential scans.

Indication Positioning

Due to geometrical configuration (tapers, radius, etc.) and inherent uncertainties associated with sound travel in austenitic materials, indication positioning may require detailed evaluation. The following information is provided to assist in proper indication positioning.

A-4

Perform detailed thickness and surface contour recordings at the location of the indication(s). Attempt to identify any position offset of the weld root in relationship to the weld centerline.

As access allows, evaluate the flaw signal amplitude responses from each side of the weld. Observe if the signal response appears reduced due to weld volume sound attenuation from one side or another.

Evaluate the ultrasonic responses from each side of the weld in both flawed and unflawed regions. Attempt to identify standard benchmark responses (e.g., weld root, weld noise, etc.) and flaw indication responses. Take notice of the ultrasonic and surface distance dimensions from these responses.

Coordinate and plot this information on a cross sectional drawing of the weld.

Note: If indications are observed using RL search units, the examiner must be aware of all ultrasonic responses inherent to longitudinal wave search units. Ultrasonic responses from both the direct shear wave and/or mode-converted wave modes may provide a more substantial amplitude response than from the direct longitudinal wave response, however, time base position (typically further in time than expected inside surface response) from these collateral responses will not provide proper flaw positioning.

Length Sizing

Length sizing should be performed utilizing information obtained on the same or nearest side of the weld as the indications. If component geometry provides limitations (e.g., geometric obstructions, welded attachments, etc.) or the flaw orientation provides improved and satisfactory UT responses, then length sizing data from opposite or far side examinations may be used to provide additional information.

If the indication is detectable with multiple search unit angles, the lower search unit angle should generally be utilized for final length determination. If geometric conditions or examination limitations prohibit adequate length sizing data with the lower search unit angle, additional angles should be utilized. If multiple angles are evaluated, the angle that provides the most conservative dimension (greatest length) should be utilized. If an extreme length discrepancy exists between search unit angles, the examiner should attempt to identify the cause of discrepancy (e.g., scan limitation, surface condition, beam spread, geometrical effects, etc.) and may utilize the length sizing measurement of a less conservative search unit.

Length sizing should be performed in a manner similar to the technique identified below. Multiple search unit angles should be evaluated in order to properly discriminate flaw responses from surrounding metallurgical and geometrical conditions.

Optimize the signal response from the flaw indication.

A-5

Scan the indication area with specific focus on the flaw signal responses, (e.g., signal shape, walk, orientation, effect of skew, etc). Adjust the system gain as needed to optimize flaw responses.

Scan an adjacent unflawed area in close proximity to the flaw area with specific focus on the surrounding geometrical responses (weld material noise, root, counterbore, etc.).

Maximize the signal response from the flaw indication. Adjust the system gain until this response is ~ 80 % FSH.

For flaws located on the far side of a weld opposite the search unit the end points should be determined by scanning along the length of the flaw in each direction until the signal response has diminished into the general background noise (full amplitude drop).

For flaws located at the centerline of the weld or on the side of the weld closest to the search unit the flaw the end points should be determined by scanning along the length of the flaw in each direction until the signal response has diminished to 20% FSH (12dB drop).

The length sizing techniques identified above provide an outside diameter length dimension which is longer than the actual inside diameter length dimension due to curvature of the piping material. To calculate the actual flaw length at the inside surface, the following formula should be used:

(ID/OD) x OD flaw length = ID flaw length.

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Figure A-1 Indication evaluation flow chart

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Appendix B: Example Utility ISI Indication Decision Trees

B-2

Revision Summary

New section. Preparer: Marc A. Brooks Date

:

Reviewer: Date

:

Supervisor – Performance Engineering

Approved: Date

:

Manager - Performance Engineering

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Information and Procedures DSN

PEP0X Revision

0 DTC

TMPEP File #

1719 IP Code

I Released By

Date

Recipient

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TABLE OF CONTENTS

1. SCOPE

2.REFERENCES

3.PERSONNEL

4.FLAW EVALUATION PROCESS

5.REPORTS

6.ACTIONS

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Procedure for Evaluation of Flaws Identified by Nondestructive Examinations

1.0 SCOPE

1.1 This Appendix defines the steps required to review indications classified as flaws during nondestructive examinations.

1.2 This procedure is to be used along with NDE procedures to determine the

acceptability of recorded indications determined to be flaws by the responsible examination personnel. This procedure used in conjunction with the indication evaluation methods established in the NDE method procedures and/or flaw sizing procedures satisfies the intent of ANSI N18.7/ANS 3.2 for operational phase special process procedures to address acceptance of items based on test results.

1.3 Flaws requiring evaluations should be documented on CARDS and will be

performed in accordance with the 2001 Edition and 2003 Addenda of ASME Section XI.

1.4 This procedure does not apply to indication classified as geometric,

metallurgical, or non-relevant indications. 2.0 REFERENCES

2.1 Applicable Nondestructive Examination Procedure 2.2 Applicable Nondestructive Flaw Sizing Procedure 2.3 ASME Section XI 2.4 ASME Section III 2.5 ASME Section II 2.6 Material Specification 2.7 Regulatory Guide 1.150, Rev 1, Alternate Method 2.8 ANSI N18.7

3.0 PERSONNEL Personnel performing flaw evaluation for acceptance need not be certified but should be an individual who is knowledgeable of NDE and analytical flaw evaluation. 4.0 FLAW EVALUATION

4.1 All indications determined to be flaws should be reported to the Owner within 24 hours of identification for entry into the corrective action system.

4.2 The responsible NDE Level III should perform the evaluation or designate an

individual knowledgeable of flaw sizing methods and application of ASME Section XI rules for flaw classification and acceptance criteria.

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4.3 Acceptance Criteria will be as specified in Table 1 4.4 Indication resolution flow paths are provided in Figures 1 and 2 for surface

and sub-surface indications. 4.5 Using the flaw size and location reported in the nondestructive examination

results perform the following: Note: Computer programs may be used to aid in calculation of flaw acceptance

but must be manually verified of treated as critical software.

A. Characterize the flaw in accordance with IWA-3000 as linear, planar, laminar, etc.

B. If multiple flaws are present determine if they are combined C. Determine if the flaw(s) are surface or subsurface by application of rules

for separation from the nearest surface. D. Determine the "a" dimension of the flaw based on its through wall

dimension and location (surface or sub-surface) E. Calculate the a/t % based on flaw dimension and component thickness F. Determine the appropriate ASME Section XI Acceptance Criteria Table

based on the component ASME classification, Category, material type, etc.

G. Determine the aspect ratio of the flaw (a/l) H. based on the aspect ratio if applicable determine the allowable length for

surface flaws or depth (a/t%) for subsurface flaws. Linear extrapolation of criteria should be performed as permitted by ASME Section XI.

I. Compare the actual flaw size to the allowed flaw size and determine accept/reject status of the flaw.

J. If no ASME Section XI acceptance criteria exists for the item or weld rules of the construction code or original design documents may be used.

4.6 For flaws exceeding the acceptance criteria of ASME Section XI in welds or

components having alternative criteria defined in a flaw handbook, the rules of the flaw handbook may be used as directed by the Owner.

4.7 For flaw exceeding the acceptance criteria of ASME Section XI where there

is no flaw handbook, the Rules of IWX-3600 (Analytical Evaluation of Flaws) may be used or the component/weld may be repaired in accordance with Owner procedures.

4.8 Analytical Evaluation per IWX-3600 must be documented in an approved engineering evaluation and accepted by the Owner and is subject to review by regulatory and enforcement authorities.

4.9 Using the indication flow path on Figures 2, 3and the rules of ASME Section

XI or other applicable Augmented rules, determine whether additional examinations are required for scope expansion.

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5.0 Definitions

following is a list of common ISI terms, additional terms and definitions may be found in ASME Section XI, IWA-9000.

Abrasion – wearing away of a surface by rubbing and friction

ASME Section XI – the eleventh section of the ASME Boiler and Pressure Vessel Code including its referenced Codes and Standards

ASME Section XI Drawings – include piping and instrument diagrams (P&IDs), isometrics, and component drawings that delineate the specific boundaries, areas, or items requiring NDE and augmented NDE

Assess – to determine by evaluation of data compared with previously obtained data such as operating data or design specifications

Augmented Requirements – those NDE required by documents other than ASME Section XI, such as: Regulatory Guides, NUREGs, NRC Generic Letters, I. E. Bulletins/Notices, FSAR, Technical Specifications, manufacturer’s recommendations, and Internal Commitments

Authorized Inspection Agency (AIA) – an organization that is empowered by an enforcement authority to provide inspection personnel and services as required by ASME Section XI

Authorized Nuclear Inspector (ANI) – an employee of an authorized inspection agency who has been qualified in accordance with NCA-5000 of Section III of the ASME Boiler and Pressure Vessel Code

Authorized Nuclear Inservice Inspector (ANII) – a person who is employed and has been qualified by an authorized inspection agency to verify that examinations, tests, and repair/replacement activities (that do not include welding or brazing) are performed in accordance with the requirements of ASME Section XI

Calibration Block Standards Drawings – the drawings that detail the specific configuration of individual standards used for calibrating ultrasonic test equipment

Cavitation – pitting of concrete caused by implosion

Code – ASME Section XI, "Rules for Inervice Inspection of Nuclear Power Plant Components," and Addenda

Code Class - ASME Section XI Classifications of 1, 2, or 3 based on the components quality group designation assigned by the owner using criteria of Regulatory Guide 1.26.

Component – an item in a nuclear power plant such as a vessel, pump, valve, or piping system

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Component Support – a metal support designed to transmit loads from a component to the load-carrying building or foundation structureComponent supports include piping supports encompass those structural elements relied on to either support the weight or provide structural stability to components.

Containment- Structures and systems designed to function as a barrier that ensures leakage of radioactive materials to the environment does not exceed the acceptable upper limit defined in 10CFR100, even if a loss of coolant accident were to occur.

Corrective Action Program - The Fermi Program that provides for evaluation and correction of conditions adverse to quality and promotes continuous improvement of plant programs, processes, and procedures, etc.

Defect – a flaw (imperfection or unintentional discontinuity) of such size, shape, orientation, location, or properties as to be rejectable

Deviation Disposition - A deviation disposition is the formal mechanism by which a deviation from a mandatory or needed element specified in an industry issues program (IP) is documented, justified, and approved.

Discontinuity – a lack of continuity or cohesion: an interruption in the normal physical structure of material or a product

Enforcement Authority – a regional or local governing body, such as a state or municipality of the United States empowered to enact and enforce Boiler and Pressure Vessel Code legislation (for example, State of Michigan)

Engineering Evaluation – an evaluation of indications that exceed allowable acceptance standards to determine if the margins required by the design specifications and construction codes are maintained

Erosion – progressive disintegration of a solid by the abrasive or cavitation action of gases, fluids, or solids in motion

Evaluation – the process of determining the significance of examination or test results, including the comparison of examination or test results with applicable acceptance criteria or previous results

Examination – the performance of visual observations and nondestructive examinations (NDE) such as radiography, magnetic particle, liquid penetrant, eddy current, and ultrasonic methods

Examination Category – a grouping of items to be examined or tested

Examination Plan – a document that provides detailed instructions for all aspects of the examination

Flaw – an imperfection or unintentional discontinuity that is detectable by nondestructive examination

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General Corrosion – an approximately uniform wastage of a surface of a component, through chemical or electrochemical action, free of deep pits or cracks

Imperfection – a condition of being imperfect, a departure of a quality characteristic from its intended condition

Indication – the response or evidence from the application of a nondestructive examination

Inservice Examination – the process of visual, surface, or volumetric examination performed in accordance with the rules and requirements of ASME Section XI

ISI Evaluation - the process that is used to evaluate ASME rules for application at Fermi as specified in MES23 (Form MES23001)

Inservice Inspection – methods and actions for ensuring the structural and pressure-retaining integrity of safety-related nuclear power plant components in accordance with the rules of ASME Section XI

Inspection – verification of the performance of examinations and tests by an Authorized Inservice inspector

Inspection Interval – as defined by regulations, a 10-year time interval during which the ISI Program is applicable using specific and Addenda of ASME Section XIThe first 10-year inspection interval commences on the date of commercial operation, with the successive intervals beginning on the date the previous interval ends. Each of the inspection intervals may be increased or decreased by as much as one year. Additionally, the interval may be extended for a period equivalent to an outage, which extends continuously for six months or more. Adjustments should not cause successive intervals to be altered by more than one year from the original pattern of intervals.

Inspection Period – duration of time within an inspection interval, (for example, first period, 0-3 years; second period, 4-7 years; third period, 8-10 years) The time frame is approximately equivalent to one-third of an interval. Refer to Table IWX-2412-1 and provisions of IWX-2412 for specific requirements and limitations. It is used for apportioning the implementation of ISI Program examinations and tests during the interval.

Inspection Program – the plan and schedule for performing examination and tests

Item – a material, part, appurtenance, piping subassembly, component, or component support

Instrument Root Valve – the first valve, in an instrument line, off of the main process line

In-Vessel-Visual-Inspection (IVVI) Program – a portion of the ISI Program that identifies the internal attachments, surfaces, welds, and components within the reactor pressure vessel boundary that require NDE during the 10-year interval.

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Nominal Operating Pressure – for Class 1 systems, the range of pressures that may normally be expected when the system is known to be operating at 100% reactor power

Nondestructive Examination – an examination by the visual, surface, or volumetric method

Open Ended – a condition of piping or lines that permits free discharge to atmospheric or containment atmosphere

Owner – the organization legally responsible for the construction and/or operation of a nuclear facility, including but not limited to one who has applied for or who has been granted a construction permit or operating license by the regulatory authority having lawful jurisdiction, i.e. Detroit Edison Co.

Preservice Inspection (PSI) –those nondestructive examinations (NDEs), including visual examinations, performed on certain ASME Class 1, 2, 3 and MC components and their supports once, prior to initial plant operations as part of the Preservice Inspection Program, or following a component repair, replacement, or modificationThe results of these examinations provide a baseline for comparison to subsequent ISI examinations.

Pressure Test Program – a portion of the overall ISI Program that identifies the components and portions of piping in ASME Class 1, 2 and 3 systems that are subject to various pressure tests during the 10-year intervalThese tests include the pneumatic, leakage, functional, or inservice types (see PEP18).

Regulatory Authority – a federal government agency empowered to issue and enforce regulations affecting the design, construction, and operation of nuclear power plants (for example, United States Nuclear Regulatory Commission)

Regulatory Issue Summaries – Document NRC endorsement of the resolution of issues addressed by industry-sponsored initiatives, solicit voluntary licensee participation in staff-sponsored pilot programs, inform licensee of opportunities for regulatory relief, announce staff technical or policy positions not previously communicated to industry or not broadly understood, and address matters previously reserved for administrative letters.

Relief Request – a written request submitted to the regulatory authority that identifies specific components that cannot be examined or tested in accordance with ASME Section XI or regulatory augmented requirementsIt includes the reason these requirements cannot be met and technical justification for performing an alternative to the requirements.

Relevant Condition – a condition observed during a visual examination that requires supplement examination, corrective measure, and correction by repair/replacement activities, or analytical evaluation

Repair – the process of restoring a nonconforming item by welding, brazing, or metal removal such that existing design requirements are met

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Safety Evaluation /Safety Evaluation Report (SER) – NRC safety evaluations (SEs) provide the regulatory bases for NRC decisions in licensing actions such as amendments, exemptions and relief requests. Safety Evaluation Reports (SERs) are generally used for more significant licensing actions such as initial licenses and renewed operating licenses. The distinction between an SE and SER is that the SER is issued as a NUREG series report. The SEs and SERs are valuable in that they provide the bases for the staff's decisions.

Source Document – any document containing requirements to which the utility is committed or that apply to the utility by virtue of law, such as federal, state and local laws and regulations.

Structural Discontinuity Welds – include circumferential weld joints at pipe-to-vessel nozzle, pipe-to-valve body, pipe-to-pump casing, pipe-to-fittings, and pipe-to-pipe of different schedule wall thickness

Structural Integrity Test – the initial or subsequent pressure test of a containment structure to demonstrate the ability to withstand prescribed loads

Technical Position – an ISI Program record that documents the details of positions taken by the utility with respect to generalized Code requirements and that do not conflict with Code requirements. These records amplify the Code requirements and provide consistent guidance for the implementation of the requirement.

Terminal Ends – the extremities of piping runs that connect structures, components or pipe anchors, each of which acts as a rigid restraint or provides at least 2 degrees of restraint to piping due to piping thermal expansion

Test – a procedure to obtain information, through measurement or observation, to determine the operational readiness of a component or system while under controlled conditions

Verify – to determine that a particular action has been performed in accordance with the rules and requirements of Section XI, either by witnessing the action or by reviewing records

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Table 1 Examination Category Item Acceptance Standard B-A, B-B Vessel Welds, Class 1 IWB-3510 B-D Vessel Nozzle Welds IWB-3512 R-A Dissimilar and Similar Metal Piping Welds IWB-3514 B-G-1 Bolting Greater than 2" diameter IWB-3515 & 3517 B-G-2 Bolting 2" and less IWB-3517 B-K-1 Integral Attachment Welds, Piping, Pump, and Valves IWB-3516 B-L-1, B-M-1 Welds in Pumps and Valves IWB-3518 B-L-2, B-M-2 Pump Casings and Valve Bodies IWB-3519 B-N-1, B-N-2, B-N-3 Interior Surfaces and Internal Components of Reactor Vessel IWB-3520 B-O Control Rod Drive Housing Welds IWB-3523 B-P Pressure Retaining Boundary IWB-3522 C-A Vessels Welds, Class 2 IWC-3510 C-B Vessel Nozzle Welds IWC-3511 C-C Integral Attachments for Vessels Piping, Pumps & Valves IWC-3512 C-D Bolting IWC-3513 C-F-1, C-F-2 Welds in Piping IWC-3514 C-G Welds in Pumps & Valves IWC-3515 C-H Pressure Retaining Components IWC-3516 5.0 REPORTS

5.1 An Indication Evaluation Summary Report should be completed for each weld or item requiring evaluation. The following information is required

A. Plant and Unit Number B. Code of Record Edition and Addenda C. Code Category D. Selected ASME Section XI Acceptance Criteria Table E. Applicable data from the NDE results reporting the flaw. F. Flaw sizing results and procedure identification G. Geometric Plots of Recorded Indication(s) H. Calculations supporting the evaluation I. Statement indicating accept or reject status

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Figure 1 Surface Exam Resolution Flow Path

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Figure 2 Volumetric Exam Resolution Flow Path

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STP 2RE14 REACTOR VESSEL 10 YR ISI DECISION TREE

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Appendix C: Example Utility Contingency Plans

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Revision Summary

New section. Preparer: Marc A. Brooks Date

:

Reviewer: Date

:

Supervisor – Performance Engineering

Approved: Date

:

Manager - Performance Engineering

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Information and Procedures DSN

PEP0X Revision

0 DTC

TMPEP File #

1719 IP Code

I Released By

Date

Recipient

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TABLE OF CONTENTS

1. PURPOSE

2. DEFINITIONS

3. SCOPE

4. PROCEDURE

5. NON-OUTAGE PROCESS

6. OUTAGE PROCESS

7. INSTRUCTIONS

8. ACTIONS ENCLOSURE 1- FERMI CONTINGENCY DETERMINATION GUIDE ATTACHMENT 1 - FERMI CONTINGENCY DETERMINATION FORM ATTACHMENT 2 - SAMPLE RECOVERY PLAN

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CONTINGENCY PLANNING PROCESS

1.PURPOSE The purpose of this instruction is to provide a consistent method for evaluating the need for and extent of contingency planning. The objective of this procedure is to develop the actions necessary to ensure that preparations are made for emergent events with significant consequences that could reasonably be anticipated to take place during work implementation. Consequences to be considered could be related to schedule, cost, dose, safety, or other site goals.

2.DEFINITIONS Contingency – any action(s) taken to prevent or alleviate negative consequences of degraded plant conditions, events, or work scope change. Contingency Plan – a plan with committed resources, equipment, parts, ready for implementation. Recovery Plan – a plan to recover from or minimize undesirable impacts of credible events that may require development of contracts, designs, work order(s) and associated parts, or other necessary resources. Risk Rank – A relative ranking of the product of probability of an event or condition occurring and the undesirable consequences of occurrence.

3.SCOPE This procedure applies to the determination and development of contingency plans for both non-outage and outage work activities that are identified as requiring a contingency review.

4.PROCEDURE The criteria listed below should be considered in determining the need for contingency plans. Outage Coordinators, Project Managers, System/Component Engineers, Work Week Managers, Supervisors, and other individuals that may be responsible for the performance of work may also require contingency plans. First time performance Previous failure history of the same or like component. Previous situations that caused outage delays Operating Experience of others with the same or like components Previous near miss safety or radiological events Low design margin or loss of robustness Previous emergent work or scope expansions MWC15 should be consulted for on-line risk management when considering actions to be taken to manage equipment safety, personnel safety, or radiological safety.

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5.NON-OUTAGE PROCESS If during the work planning process, and activity is identified to have a substantial potential for undesirable outcomes, this procedure will be implemented by the responsible work leader to determine the need and extent of contingency planning.

6.OUTAGE PROCESS Contingency identification and planning milestone dates are specified per the outage milestone schedule. Team Leaders will review their work in accordance with this procedure for possible contingency plans. The plans will be presented in a challenge meeting and should be approved by the Outage Manager.

7.INSTRUCTIONS Enclosure 1 is the Contingency Determination Guide and describes the information to be provided. The Contingency Determination Form (Attachment 1) should be completed as required for inspections, tests, or other activities that have a significant risk of undesirable outcomes. 1) Complete the Contingency Determination Form (Attachment 1) as follows: 2) Identify the item or category of component to be evaluated. 3) Identify the scope of the work. 4) Evaluate events, conditions, and impacts using the guidance provided in Enclosure A.

a) Provide a brief description of events or conditions that are applicable to the activity being evaluated.

b) Mark N/A if item is not applicable. c) Provide a relative risk ranking score for each of the credible events or conditions

described. i) Not applicable - 0 ii) Low - 1 iii) Medium - 2 iv) High - 3

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5) Determine the sum of the largest risk ranking for an event or condition and the largest risk ranking of the impacts listed.

a) If the sum equals 2 or 3 no contingencies are required. b) If the sum equals 4 contingencies should be evaluated and reviewed in group challenge

meetings. Lead time for contingency plan implementation should be less than 50% of the schedule float time for the activity and should be able to be completed within 100% of the allowable float time. The contingency plan should include committed equipment, parts, and resources necessary for implementation.

c) If the sum equals 5 or 6 contingencies should be evaluated and a contingency or recovery plan should be ready for immediate implementation.

Note: If the contingency or recovery plan would result in significant schedule delays, or significantly increased cost or dose increases, the plan and associated contingencies should be reported to and reviewed by Nuclear Engineering Management.

8.ACTIONS 1) Develop a “Contingency Plan” including schedule layout, work orders, designs, parts,

contracts, etc. to identify and commit the needed resources for designated activities.

a) Plan a work package. b) Consider use of USA . c) Establish contracts for specialty work.

2) Develop “Recovery Plan” to address lower risk activities.

a) Identify a recovery team leader. b) Have draft EFA or ISI Evaluation written and reviewed, or ready for approval. c) Have a written and approved Recovery Plan using the attached form with supplemental

pages as necessary. d) Identify key resources and contractors and establish a contact. e) Discuss schedule considerations. f) Schedule activities to identify risk early in the outage. g) For complex Recovery Plans, provide a details schedule including decision points.

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ENCLOSURE 1 FERMI CONTINGENCY DETERMINATION GUIDE

Item: Describe work activity Scope: Describe work scope or duration

EVENT OR CONDITION

Known Issues at Fermi

Change in Technique

New Industry Experience

First Time Inspection / Test

More Stringent Acceptance

Criteria

Condition Cannot Be Accepted by

Evaluation

Mitigating Factors

Description: Are there known issues or concerns with the history of test or examination results, especially those issues or concerns that indicates problems may be encountered?

Is there a change in the method used to perform the exam or test which could significantly and adversely change the expected results?

Are there new industry experiences applicable to degradation or failure of a components scheduled for examination or testing?

Is this the first time a test or examination of components is being performed, particularly on components that have been in service for a period of time?

Have the acceptance criteria or standards been made more restrictive, thereby increasing the potential of more test failures?

Is there a potential that test results cannot be accepted by Engineering Evaluation, and the failed condition must be corrected by repair or replacement prior to return of the component to service?

Are there conditions that mitigate events or conditions that make Fermi conditions different than those experienced at other plants?

Risk Ranking: Low =1, Med = 2,

High = 3

# # # # # #

IMPACT Outage Schedule Delay

Significant Cost Increase

Significant Dose Increase

Reduction of Regulatory

Margin

Reduction in Plant Safety

Reduction in Personnel Safety

Other

Description: Assuming the worst case result of credible failure(s), is there a potential to impact pre-outage or outage schedule?

Assuming the worst case result of credible failure(s), is there a potential to impact station budget or outage costs?

Assuming the worst case result of credible failure(s), is there a potential to impact group or station radiation exposure goals?

Assuming the worst case result of credible failure(s), is there a potential to impact regulatory margin?

Assuming the worst case result of credible failure(s), is there a potential to impact plant safety margins or defense in depth?

Assuming the worst case result of credible failure(s),

what other personnel safety

measures should be considered?

Assuming the worst case result of credible failure(s), what other impacts

should be considered?

Risk Ranking: Low =1, Med = 2,

High = 3

# # # # # #

Risk Sum: High Event + High Impact

High Event #

High Impact #

Sum Total

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CONTINGENY

Schedule Recovery Plan Work order Parts Design Contracts Other

Risk Sum 4-6 Contingency or

Recovery required

Risk Sum 2-3

Contingency not required

Are there scheduling considerations that should be made to prevent or reduce adverse consequences.

What actions are proposed but do not have work orders planned or resources and parts committed?

What work order, Section XI Programs, SOEs, EFA’s or other work documents need to be prepared to implement a contingency plan?

What parts that are not stock items need to be obtained to implement the contingency or recovery plan?

What design or calculations need to be completed to implement the contingency or recovery plan?

What contracts need to be initiated to implement the contingency or recovery plan?

What Licensing Support, Procedures, Regulatory approvals, or other actions need to be taken to allow the contingency plan or recovery plan to be implemented.

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ATTACHMENT 1 FERMI CONTINGENCY DETERMINATION FORM

Item: Describe work activity Scope: Describe work scope or duration

EVENT OR CONDITION

Known Issues at Fermi

Change in Technique

New Industry Experience

First Time Inspection / Test

More Stringent Acceptance

Criteria

Condition Cannot Be Accepted by

Evaluation

Mitigating Factors

Description: Risk Ranking:

Low =1, Med = 2, High = 3

# # # # # #

IMPACT Outage Schedule Delay

Significant Cost Increase

Significant Dose Increase

Reduction of Regulatory

Margin

Reduction in Plant Safety

Reduction in Personnel Safety

Other

Description: Risk Ranking:

Low =1, Med = 2, High = 3

# # # # # #

Risk Sum: High Event + High

Impact

High Event #

High Impact #

Sum Total

CONTINGENY Schedule Recovery Plan Work order Parts Design Contracts Other Risk Sum 4-6

Contingency or Recovery required

Risk Sum 2-3

Contingency not required

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ATTACHMENT 2

Sample Recovery Plan

Recovery Plan Team Leader: _____________________________________ Alternate Team Leader: _____________________________________

A. Reason for development of the Recovery Plan.

B. Brief description of the Recovery Plan:

C. List support services needed (contacts, phone numbers, and contract numbers):

D. List any testing requirements (PMT, IPTE, or SOE):

E. List any licensing support (License amendments and exempts):

F. Attach any preplanned analysis or evaluations (EFAs, ISI Evaluation):

G. Attach any agreements to share resources (USA, Vendor Contracts):

H. Discuss schedule considerations. For complex Recovery Plans, attach a detailed schedule and decision tree as appropriate.

Prepared by: _____________________________________ Approved by: _____________________________________

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Example Contingency Table

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Electric Power Research Institute 3420 Hillview Avenue, Palo Alto, California 94304-1338 • PO Box 10412, Palo Alto, California 94303-0813 USA

800.313.3774 • 650.855.2121 • askepri@epri.com • www.epri.com

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conducts research and development relating to the generation, delivery

and use of electricity for the benefit of the public. An independent,

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as well as experts from academia and industry to help address

challenges in electricity, including reliability, efficiency, health, safety and

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analyses to drive long-range research and development planning, and

supports research in emerging technologies. EPRI’s members represent

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the United States, and international participation extends to more than

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Program:

Nondestructive Evaluation

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