asme companion

22
CHAPTER 28 28.1 INTRODUCTION This chapter discusses the general requirements of Section XI applicable to all classes of components, including steel vessels, piping, pumps, valves, and concrete structures. It identifies the limits of applicability of Section XI—that is, elements that are within and elements that are outside the scope of the Code. Interfaces with any applicable regulatory requirements are addressed, and the use of Code editions and addenda and Code Cases is explained. In addition, this chapter describes periodic nondestructive examination and pressure testing used to ensure the integrity of components (other than containment vessels) within the scope of the Code’s jurisdiction. The requirements of nondestructive examination (NDE) are specified, ranging from personnel qualification to the overall conduct of the examinations, as are the types of NDE required, including sample expansion, and the frequency of examinations required, such as from the detection of defects. Periodic pressure testing and pressure testing following repair/replacement activities are addressed, as are the responsibilities and Quality Assurance (QA) Program require- ments of the different entities involved in the examination and testing of a nuclear power plant. Controversial issues and topics of current concern, including the applicability of recent United States Nuclear Regulatory Commission (USNRC) Generic Letters and Information Notices, are addressed, and ways in which the reader can use recent Section XI revisions to his or her advantage are described. As a benefit to the reader, this chapter references some published ASME interpretations to explain how the Code requirements can be applied to commonly encountered problems. Until recently, the ASME Code has had rather haphazard refer- ences to S.I., or metric, units. Beginning with the 2004 Edition, the entire Boiler and Pressure Vessel Code, including Section XI, contains S.I. units, along with the US customary units. Either set of units may be used. However, because values in the two systems are not exact equivalents, each system must be used independently of the other without mixing the two systems. So, the user must select one set of units and sticks with it, for all work and all evalu- ations. The S.I. units have been rounded, for the convenience of the international user. For example NPS 1 has been converted to DN 25, rather than being precisely converted to 25.4 mm. 28.2 PREFACE The preface is unique to Section XI; there is no parallel in other sections of the ASME Boiler and Pressure Vessel Code. However, the preface does not contain any unique requirements; instead, it introduces the reader to Section XI. The preface summarizes the scope and application of IWA- 1000. It describes the responsibilities of the Owner identified in IWA-1400 for the preparation of a program to implement the Section XI requirements. The preface also summarizes some of the Authorized Nuclear Inservice Inspector (ANII) responsibili- ties, which are further delineated in IWA-2110. A few minor dif- ferences exist between the requirements in the preface and those in the text; for those few cases, a common practice is to allow the provisions in Subsection IWA to supersede those in the preface. In the 2003 Addenda, the Preface was revised to address the issue of plant aging. The intended message of this revision is that the requirements of Section XI provide a way to manage the effects of aging in both the initial and license renewal term. 28.3 ORGANIZATION The organization section is similar to that in Section III, and like the preface, does not contain any requirements. Its purpose is to facilitate an understanding of the way Section XI is organized and to explain the common shortcuts used in referencing other sections of the ASME Boiler and Pressure Vessel Code, as well as non-ASME documents. The organization identifies the three divisions of Section XI. Division 1 is the subject of this book’s chapter; it provides require- ments for light-water cooled nuclear power plants. Division 2 covers gas-cooled plants, whereas Division 3 covers liquid-metal cooled- plants. At the time of this writing, no nuclear power plant anywhere in the world is implementing Division 2 or Division 3. Division 2 and Division 3 have been deleted from Section XI because of a lack of interest in their use. There is currently effort underway to rewrite Division 2 to provide inservice inspection requirements for the next generation of high-temperature, modular, gas-cooled reactors. This effort has been accelerated by the need to develop an inservice SECTION XI: RULES FOR INSERVICE INSPECTION AND TESTS OF NUCLEAR POWER PLANT COMPONENTS Richard W. Swayne ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 1

Upload: david-ambrose-bell-moffat

Post on 27-Apr-2015

208 views

Category:

Documents


3 download

TRANSCRIPT

Page 1: Asme Companion

CHAPTER

28

28.1 INTRODUCTION

This chapter discusses the general requirements of Section XIapplicable to all classes of components, including steel vessels,piping, pumps, valves, and concrete structures. It identifies thelimits of applicability of Section XI—that is, elements that arewithin and elements that are outside the scope of the Code.Interfaces with any applicable regulatory requirements areaddressed, and the use of Code editions and addenda and CodeCases is explained. In addition, this chapter describes periodicnondestructive examination and pressure testing used to ensurethe integrity of components (other than containment vessels)within the scope of the Code’s jurisdiction. The requirements ofnondestructive examination (NDE) are specified, ranging frompersonnel qualification to the overall conduct of the examinations,as are the types of NDE required, including sample expansion,and the frequency of examinations required, such as from thedetection of defects. Periodic pressure testing and pressure testingfollowing repair/replacement activities are addressed, as are theresponsibilities and Quality Assurance (QA) Program require-ments of the different entities involved in the examination andtesting of a nuclear power plant. Controversial issues and topicsof current concern, including the applicability of recent UnitedStates Nuclear Regulatory Commission (USNRC) Generic Lettersand Information Notices, are addressed, and ways in which thereader can use recent Section XI revisions to his or her advantageare described. As a benefit to the reader, this chapter referencessome published ASME interpretations to explain how the Coderequirements can be applied to commonly encountered problems.

Until recently, the ASME Code has had rather haphazard refer-ences to S.I., or metric, units. Beginning with the 2004 Edition,the entire Boiler and Pressure Vessel Code, including Section XI,contains S.I. units, along with the US customary units. Either setof units may be used. However, because values in the two systemsare not exact equivalents, each system must be used independentlyof the other without mixing the two systems. So, the user mustselect one set of units and sticks with it, for all work and all evalu-ations. The S.I. units have been rounded, for the convenience ofthe international user. For example NPS 1 has been converted toDN 25, rather than being precisely converted to 25.4 mm.

28.2 PREFACE

The preface is unique to Section XI; there is no parallel in othersections of the ASME Boiler and Pressure Vessel Code. However,the preface does not contain any unique requirements; instead, itintroduces the reader to Section XI.

The preface summarizes the scope and application of IWA-1000. It describes the responsibilities of the Owner identified inIWA-1400 for the preparation of a program to implement theSection XI requirements. The preface also summarizes some ofthe Authorized Nuclear Inservice Inspector (ANII) responsibili-ties, which are further delineated in IWA-2110. A few minor dif-ferences exist between the requirements in the preface and thosein the text; for those few cases, a common practice is to allow theprovisions in Subsection IWA to supersede those in the preface.

In the 2003 Addenda, the Preface was revised to address theissue of plant aging. The intended message of this revision is thatthe requirements of Section XI provide a way to manage theeffects of aging in both the initial and license renewal term.

28.3 ORGANIZATION

The organization section is similar to that in Section III, andlike the preface, does not contain any requirements. Its purpose isto facilitate an understanding of the way Section XI is organizedand to explain the common shortcuts used in referencing othersections of the ASME Boiler and Pressure Vessel Code, as well asnon-ASME documents.

The organization identifies the three divisions of Section XI.Division 1 is the subject of this book’s chapter; it provides require-ments for light-water cooled nuclear power plants. Division 2 coversgas-cooled plants, whereas Division 3 covers liquid-metal cooled-plants. At the time of this writing, no nuclear power plant anywherein the world is implementing Division 2 or Division 3. Division 2and Division 3 have been deleted from Section XI because of a lackof interest in their use. There is currently effort underway to rewriteDivision 2 to provide inservice inspection requirements for the nextgeneration of high-temperature, modular, gas-cooled reactors. Thiseffort has been accelerated by the need to develop an inservice

SECTION XI: RULES FOR INSERVICE

INSPECTION AND TESTS OF NUCLEAR

POWER PLANT COMPONENTS

Richard W. Swayne

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 1

owner
Cross-Out
owner
Callout
liquid-metal-cooled
Page 2: Asme Companion

2 • Chapter 28

inspection program for a reactor being designed for licensing andconstruction by PBMR in South Africa.

Not coincidentally, the construction of Section XI is modeledafter that of Section III, for Section XI was first written by theSubgroup on Inservice Inspection of Subcommittee III. SubsectionIWA contains general requirements applicable to all classes of com-ponents and supports, but the other Subsections are more restrictivein their requirements. Subsection IWB covers requirements forClass 1 components; Subsection IWC covers Class 2 components;Subsection IWD covers Class 3 components; Subsection IWEcovers Class MC metal containment vessels and containment pene-trations not backed by concrete, as well as the liners of Class CCcontainment vessels; Subsection IWF covers Class 1, 2, 3, and MCcomponent supports; Subsection IWG is anticipated to eventuallycover core support structures and reactor vessel internal structures,although presently it is in course of preparation; and SubsectionIWL covers concrete containment vessels.

Subsections IWP and IWV were part of Section XI until the1988 Addenda, at which time the responsibility for these oper-ability requirements was transferred to the ASME Committee onOperation and Maintenance (O&M Committee). As the responsi-bilities for pump, valve, and snubber testing requirements weretransferred to the O&M Committee, and the USNRC now refer-ences the OM Code to mandate these requirements, all referencesto these requirements have now been removed from Section XI.Section XI now contains only a few footnotes to remind the userthat there may be requirements in the OM Code for testing subse-quent to repair/replacement activities. Furthermore, due to con-flicting requirements between Section XI and the OM Code forsnubber examinations, a recent change to IWF-5400 removed therequirements for inservice inspection of snubbers.

The next part of the organization section describes the termi-nology used to identify successively smaller parts of the require-ments. The description is helpful, for it allows the reader tounderstand the way certain parts of Section XI are referenced byother parts. The operative principle is that the part referenced is tobe met in its entirety; no requirements outside the referenced partare intended to be included in the reference. For example, the ref-erence in IWA-4820(a) to IWB-2200 is intended to include thetext from IWA-2200 through IWA-2240 that is, up to but notincluding IWA-2300.

The last part of the organization section identifies shortcutsused by the Committee to identify other Sections of the ASMEBoiler and Pressure Vessel Code, such as Section II, Parts A andB, as well as Sections III, V, and IX. The publishers of variousstandards are referenced, including the American Society forTesting and Materials (ASTM), the American Society forNondestructive Testing (ASNT), the American Concrete Institute(ACI), the American Public Health Association (APHA), and theAmerican Welding Society (AWS). Parts of the U.S. Code ofFederal Regulations (CFR) and technical reports published by theElectric Power Research Institute (EPRI) are also referenced.

The organization section refers to two kinds of appendices thatare part of Section XI: Mandatory and Nonmandatory Appendices.Each Mandatory Appendix is identified with a Roman numeral(such as Appendix III) that must be followed whenever the user isperforming an activity within the scope of this Appendix. A Non-mandatory Appendix, on the other hand, is identified with a capitalletter. This Appendix is provided either as an acceptable method ofcomplying with a specified Section XI requirement or as a guidefor performing optional activities—that is, those that are not at all

required by Section XI. In addition, the Nonmandatory Appendixis generally provided to show industry endorsement of USNRC-approved practices that many Owners have applied.

28.4 ARTICLE IWA-1000: SCOPE ANDRESPONSIBILITY

28.4.1 IWA-1100: Scope The scope of Section XI is significant for one reason: it limits the

Section XI applicability to dealing with degradation detected byperiodic inservice inspection, and to repair, replacement, and modi-fication activities performed for any reason. The ASME Boiler andPressure Vessel Committee has interpreted that the requirements ofSection XI do not apply to flaws identified at times other than dur-ing periodic inservice inspection or repair replacement activities, asexpounded by the following interpretations:

Interpretation XI-1-92-19:

Question (1): Does leakage identified during the conduct of avisual (VT-2) examination performed in conjunction with aSection XI required pressure test (Table IWA-5210-1), exceed-ing the acceptance criteria of IWB-3000, IWC-3000, andIWD-3000, require corrective measures in accordance withIWA-5250(a) prior to continued service?

Reply (1): Yes.

Question (2): Does leakage identified during the conduct ofnormal plant operation not in conjunction with a Section XIrequired pressure test (Table IWA-5210-1) require correctivemeasures in accordance with IWA-5250(a)?

Reply (2): No. Section XI, IWA-5250(a) does not apply duringnormal plant operation.

Interpretation XI-1-92-03:

Question: Do the provisions of Section XI, IWA-5250 apply toleakage found at times other than during a system pressuretest?

Reply: No.

Interpretation XI-1-89-67:

Question: Is it a requirement of Section XI that additionalexaminations be performed within the same ExaminationCategory for flaws detected outside the course of an inserviceexamination that exceed the standards of IWB/IWC/IWD/IWF-3000?

Reply: Section XI does not address additional examinations forflaws detected outside the course of an inservice examination.

The basis for these interpretations may be more easily under-stood through the use of Fig. 28.1. This figure graphically depictsinservice degradation and restoration through repair/replacementactivities. At the start of operation, a given item (e.g., a compo-nent, part, weld, or piece of material) meets all technical require-ments of the applicable Construction Code. By that time, the itemwill also have passed a specified preservice inspection to have abaseline established for future inservice inspections. During oper-ation, the item is subject to degradation from many differentmechanisms, such as erosion, corrosion, and fatigue.

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 2

Page 3: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 3

After a specified period of time, the equipment is subject toinservice inspection, consisting of a specified nondestructiveexamination. One expects that at least some of the required exam-inations will reveal a form of degradation, such as thinning orcracks. The item may thus be in a state in which it no longer com-plies with the requirements imposed on it during construction.This degradation is then evaluated against the specified flawacceptance criteria of Section XI. If it meets this criteria, noaction is required, and operation is continued.

Following another specified interval, usually about ten years,the item is reexamined. If the degradation then results in the flawexceeding the Section XI acceptance standards, repair or replace-ment is required. The required repair/replacement activity mustgenerally restore the item to compliance with the ConstructionCode (although some exceptions are permitted). Following therepair/replacement activity, operation is again continued until thenext inservice inspection, which is again about ten years.

The referenced interpretations that follow include several exam-ples of how Section XI does not provide requirements for the eval-uation and acceptance of flaws identified by means other than arequired inservice inspection or examination. Thus, if a flaw isfound by other than a required inservice examination, no correc-tive action is prescribed by Section XI. However, the Committeehas interpreted that IWA-4000 (IWB/IWC/IWD/IWE/IWF/IWL-4000) is always applicable to repair/replacement activities, regard-less of the reason for the activity (this applicability is also true forIWB/IWC/IWD/IWE/IWF/IWL-4000). Therefore, if repair orreplacement is chosen as an optional corrective action for a flawfound by other than a required examination (even though the needfor corrective action is outside the scope of Section XI), compli-ance with IWA-4000 is required for the repair/replacement activity.The following two interpretations pertain to these facts:

Interpretation XI-1-89-64R:

Question (1): Is it the intent of Section XI that if through-wallleakage, other than at a mechanical connection, is discoveredin an ASME Class 1, 2, or 3 component, that the repair orreplacement be performed in accordance with IWA-4000 orIWA-7000, respectively?

Reply (1): Yes.

Question (2): If through-wall leakage is detected at otherthan at a mechanical connection, in an ASME Class 3 pres-sure-retaining component, during a scheduled system pres-sure test, is it the intent of Section XI that the Owner deter-mines whether the flaw represents an isolated or a genericcondition?

Reply (2): Yes.

Question (3): If through-wall leakage is detected at other thanat a mechanical connection, in an ASME Class 3 componentduring a scheduled system pressure test (Item D1.10), is theOwner required to evaluate the inservice degradation and todocument the results?

Reply (3): Yes. Section XI, IWA-1400(i) and IWA-5250(a)require that the Owner evaluates the sources of leakage, andIWA-6000 requires that the Owner documents theseevaluations.

Interpretation XI-1-89-28:

Question: Is it the intent of Section XI, Division 1, that IWA-4000 and IWF-4000 be used when a component support isrepaired regardless of how the nonconformance was identi-fied?

Reply: Yes.

28.4.2 IWA-1200: Jurisdiction With limited exceptions, Section XI may not be applied to con-

struction of a component which is, the jurisdiction of the variousConstruction Codes although it may be applied to a componentimmediately upon completion. The exceptions include entire newpiping systems, which are now within the scope of IWA-4000,and replacement parts, appurtenances, piping subassemblies andsupports, fabricated by a Repair/Replacement Organization. (Foradditional details, see Sections 27.8.1 and 27.5.3.) In the case ofan item constructed in accordance with any part of the ASMEBoiler and Pressure Vessel Code, Section XI may be applied uponcompletion of the Data Report and the application of the CodeSymbol Stamp. However, until the component is placed in opera-tion, either Section XI or the applicable Construction Code maybe applied. In either case, the technical requirements of theConstruction Code must be met for any repair/replacement activi-ties performed on the component. However, the administrativerequirements of either the Construction Code or Section XI maybe applied, which means, for example, that repair/replacementactivities on an item damaged by the Owner or found to be defec-tive during installation may be controlled under an N-typeCertificate Holder’s QA Program or under the Owner’s QAProgram and may be documented on either a Section III DataReport or a Form NIS-2, as applicable. Interpretation XI-1-98-03states the following:

Question (1): Is it the intent of Section XI that the rules ofeither Section III or Section XI, as determined by the Owner,apply to the repair or replacement of a component, manufac-tured to Section III requirements, subsequent to its being N-or NV-stamped, but prior to installation?

Reply (1): Yes.

FIG. 28.1 QUALITY OR LEVEL OF COMPLIANCE WITHCONSTRUCTION CODE TECHNICAL REQUIREMENTS

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 3

Page 4: Asme Companion

4 • Chapter 28

28.4.3 IWA-1300: Application and Classifications Section XI is not written by the ASME as a mandatory require-

ment; it becomes mandatory only when imposed by law, as from aregulatory or enforcement authority. In the United States, Title 10 of the Code of Federal Regulations (CFR) Energy, mandatesuse of Section XI for operating nuclear power plants. Similarly, inmany other countries the applicable regulatory body mandates useof Section XI. Section XI does not specify what components areto be subjected to Section XI requirements or which requirementsare to be applied to which components, so the components mustbe classified accordingly by the Owner before implementation ofSection XI is possible.

Requirements and guidance for classification may be found in10CFR50.2, Definition of Reactor Coolant Pressure Boundary;10CFR50.55a, Codes and Standards; the USNRC RegulatoryGuide 1.26, Quality Group Classifications and Standards forWater–, Steam–, and Radioactive Waste–Containing Componentsof Nuclear Power Plants (for Comment); and the USNRCNUREG-0800, Standard Review Plan.

Components classified by the Owner as Class 1, 2, or 3 aresubject to the requirements of Subsection IWB, IWC, and IWD,respectively.

Section XI permits optional increases in classification over thatrequired by the regulatory authority for construction or inserviceinspection, independently. For example, a component optionallyconstructed to Class 2, when the regulatory authority permits con-struction to Class 3, may be inspected in accordance withSubsection IWB, IWC, or IWD at the option of the Owner.

28.4.4 IWA-1400: Owner’s Responsibility The Owner’s responsibilities identified in IWA-1400 are mostly

a summary of actions required by other parts of Section XI.However, the following two significant Owner’s requirements arenot described elsewhere in Section XI.

(1) The Owner must submit the inspection plans of IWA-2420to the enforcement and regulatory authorities having juris-diction at the plant site.

(2) The Owner must have a QA Program meeting the require-ments of 10CFR50 Appendix B, “Quality AssuranceCriteria for Nuclear Power Plants and Fuel ReprocessingPlants,” or ASME NQA-1, “Quality Assurance ProgramRequirements for Nuclear Facilities.”

The requirement of item (2) is probably superfluous, for10CFR50 Appendix B is imposed by the USNRC; outside theUnited States, similar requirements are imposed by many regula-tors. Compliance with NQA-1 is generally considered sufficientto satisfy the requirements of Appendix B, but because AppendixB is much more vague than NQA-1, it has sometimes been inter-preted differently.

28.4.5 IWA-1600: Referenced Standards and Specifications

To facilitate the referencing of other Codes and Standards, andalso to maintain consistent references to the specific Edition andAddenda of those documents endorsed by Section XI, a list ofthose Codes and Standards with the endorsing Edition andAddenda is provided. Whenever one of these documents is refer-enced by Section XI, the reader must look in Table IWA-1600-1to find the applicable edition and addenda of that document.

28.5 ARTICLE IWA-2000: EXAMINATIONAND INSPECTION

28.5.1 IWA-2100: Authorized Inspection Arguably one of the most important elements of the ASME

Boiler and Pressure Vessel Code is the function of the indepen-dent or third-party inspector. The ANII is commissioned by theNational Board of Boiler and Pressure Vessel Inspectors (orsimply the National Board) and is usually endorsed by the stateor province in which he or she works. The ANII must beemployed by an organization accredited by the ASME to pro-vide these services. By signing the Form NIS-1, NIS-2, or (inCase N-532) an alternative, the ANII provides independent veri-fication that all applicable Section XI requirements have beenmet. As described in Section 28.5.6, the ANII may also permitsome specific alternatives to the prescribed examination meth-ods of Section XI.

The organizations accredited to provide these services may beprivate organizations or departments of governmental agencies. Incountries outside of the United States, other, nonaccredited orga-nizations, such as the Canadian Provincial Inspectors, often per-form a similar though perhaps not equivalent function.

IWA-2110 delineates the responsibilities of the ANII, providingthe ANII with some authority to require certain actions of theOwner whenever he or she considers such action necessary toensure Code compliance. For ANIIs to satisfactorily perform theirduties, Owners must provide them with the necessary access totheir plants.

28.5.2 IWA-2200: Examination Methods There are three types of examinations used during inservice

inspections: visual, surface, and volumetric. Each type includesone or more methods, each of which may be performed by usingone or more techniques.

Nonmandatory Appendix D is referenced to provide guidancefor preparing surfaces before conducting a nondestructive exami-nation. This Nonmandatory Appendix is particularly useful forpreparing internal counterbores for ultrasonic examination ofClass 1 or 2 piping welds.

28.5.3 IWA-2210: Visual Examination There are three types of visual examination for Class 1, 2, and

3 components and their supports: the VT-1, VT-2, and VT-3. (SeeIWE and IWL for separate examination requirements for contain-ment vessels.) The VT-1 visual examination entails a close scrutinyof the component or weld surface, searching especially for cracksand corrosion. The VT-2 visual examination is conducted solelyfor detection of leakage during conduct of a required pressuretest. The VT-3 visual examination may be conducted from agreater distance than that required for the VT-1 visual examina-tion. It is appropriately suited for identifying gross corrosion ordistortion and missing or broken items.

For the VT-1 and VT-3 visual examinations, remote examina-tion may be substituted for direct examination. To be consideredviable, the remote examination procedure must be demonstratedto resolve the selected test chart characters.

It is not necessary to measure illumination levels on eachexamination surface when the same portable light source or sim-ilar installed lighting equipment is demonstrated to provide thespecified illumination at the maximum examination distance.However, the illumination levels from battery-powered portablelights must be checked before and after each examination or

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 4

owner
Callout
,
Page 5: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 5

. . . series of examinations, not to exceed four hours betweenchecks.

Recent addenda have added an alternative to meeting the light-ing requirements for the VT-1 and VT-3 visual examinations. Inlieu of measuring the lighting, the examiner may demonstrate theability to resolve small characters on a test card at the conditionspresent during the examination. If these characters can beresolved by the examiner, under the test conditions, the lightingrequirements may be waived.

28.5.4 IWA-2220: Surface Examination Surface examinations include magnetic particle, liquid pene-

trant, and eddy current methods. Magnetic particle examinationthrough coatings is also permitted. In the 2001 Edition, ultrasonicexamination (UT) was added as a surface examination method forCategory B-F and B-J piping welds, when the ultrasonic examina-tion is performed from the inside surface. These ultrasonic exami-nations are capable of detecting surface flaws on the outsidesurface. Therefore, instead of removing shielding, removing insu-lation, performing surface preparation, and performing surfaceexaminations on the outside surface, this ultrasonic examinationmay be substituted for the required surface examination.

In the 2004 Edition, the minimum lighting requirements fornonfluorescent magnetic particle and liquid penetrant surfaceexamination were revised to be consistent with each other andwith the lighting requirements for Section XI visual examinations.IWA-2221 and IWA-2222 take exception to the Section V mini-mum lighting requirement of 100 fc and provide a lower limit of50 fc, if lighting intensity is used, rather than the standard testchart character height limits. The 2004 revision provided consis-tent requirements for lighting during performance of nonfluores-cent surface examinations and permitted use of the IWA-2210character chart, in lieu of a light meter, for verification of ade-quate lighting.

28.5.5 IWA-2230: Volumetric Examination Volumetric examinations include radiographic, ultrasonic, and

eddy current methods. They may be conducted from either theinside or the outside surface of a component. Radiography is notoften practical because of normal radiation levels in Class 1 sys-tems. Compared to radiography, ultrasonic examination is usuallymore sensitive to the kinds of fine cracks that may be inducedduring operation, and is thus normally the examination method ofchoice for Class 1 and 2 systems. The eddy current method is usu-ally limited to examination of pressurized water reactor (PWR)steam-generator tubing.

A significant new advancement in radiography–phosphor imag-ing is now permitted. This method allows much shorter expo-sures, using lower radiation levels, and permits digital imageenhancement and storage. Use of this technique should permitreductions in outage delays caused by radiographic examinations(mostly related to repair/replacement activities).

Another significant change currently planned for the 2009Addenda, is addition of provisions for use of ultrasonic examina-tion in lieu of radiographic examination (UT in lieu of RT). Theseprovisions are already permitted for Sections I, III, VIII, and XIIapplications via use of Cases N-659, “Use of UltrasonicExamination in Lieu of Radiography for Welds in Class 1, 2, and3 Components, Section III, Division 1,” and 2245, “Use ofUltrasonic Examination in Lieu of Radiography, Section I;Section VIII, Divisions 1 and 2; and Section XII.” Use of UT inlieu of RT for Section XI applications will be limited mostly to

substituting ultrasonic examination for radiographic examinationrequired by Section III for repair/replacement activities.

28.5.6 IWA-2240: Alternative Examinations Alternative examination methods, a combination of methods, or

newly developed techniques may be substituted for the methodsspecified in Section XI. However, the Owner must demonstrate tothe satisfaction of the ANII that the results are equivalent or supe-rior to those of the specified method.

This subsubarticle gives the ANII considerable latitude inallowing alternative nondestructive examination (NDE) methodsor techniques, although the burden of proof rests with the Owner.Such methods and techniques are usually used for such mundaneconcerns as allowing use with the 1989 Edition of the calibrationblock added with Appendix VIII in the 1989 Addenda. This pro-vision could be used for something as novel as acoustic emissioninstead of radiography, although it might be difficult to persuadean ANII that acoustic emission is equivalent or superior to radiog-raphy in any potential applications.

28.6 IWA-2300: QUALIFICATIONS OFNONDESTRUCTIVE EXAMINATIONPERSONNEL

28.6.1 IWA-2310: General The Owner is required to prepare a written practice that meets

the requirements of ASNT CP-189, Standard for Qualificationand Certification of NDE Personnel, which replaced SNT-TC-1Ain Section XI. These ASNT documents are written as standardsfor guidance in preparation of NDE personnel qualification pro-grams, but they are made mandatory by reference in Section XI.Section XI has taken exception to the CP-189 requirement thatLevel III personnel obtain an ASNT Level III Certificate. LevelsI, II, and III personnel are required to be recertified by qualifica-tion examination every five years. Until recently, Levels I and IIpersonnel were required to be recertified by examination everythree years; presently, however, the certification period for per-sonnel of all three levels is five years.

NDE certifications are valid until their expiration (see IWA-2314, below), even when Owners change the basis of their writtenpractices to use later versions of SNT-TC-1A or CP-189 beforethe expiration of their certification. In addition, NDE certifica-tions meeting any edition or addenda of IWA-2300 are consideredcompliant with the provisions of IWA-2300 of any earlier editionand addenda. The following two interpretations note these facts:

Interpretation XI-1-92-42:

Question: Does Section XI, IWA-2300 provide that certifica-tions based on a procedure in accordance with SNT-TC-1Aunder Section XI Editions and Addenda prior to 1988 remainvalid until recertification is required?

Reply: Yes.

Interpretation XI-1-92-70:

Question (1): Is it the intent of Section XI (1989 edition with1991 addenda), IWA-2325, that the Level III Basic, Method,Specific, and Practical examinations be separate parts of thetotal personnel qualification examination process, and carryequal weight when determining the final average score?

Reply (1): Yes.

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 5

Page 6: Asme Companion

6 • Chapter 28

Question (2): Is it the intent of Section XI that nondestruc-tive and visual examination personnel qualified and certi-fied in accordance with IWA-2300 of any Edition andAddenda of Section XI are qualified and certified to performexaminations required by all earlier editions and addendaof Section XI?

Reply (2): Yes.

Qualifications for NDE methods listed in CP-189 must be inaccordance with CP-189, but they must also be based on themethods and techniques required by Section XI. Qualifications forNDE methods not listed in CP-189 must be as defined in CP-189.

Section XI also provides additional requirements for training,qualification, and certification of ultrasonic examination (UT)personnel in Mandatory Appendix VII.

In lieu of meeting the requirements of CP-189, VT-2 visualexamination personnel may be certified by meeting the followingrequirements:

(1) At least 40 hr. of plant walkdown experience. (2) At least 4 hr. of training in the Section XI VT-2 visual exam-

ination requirements and plant-specific VT-2 visual exami-nation procedures.

(3) A vision test in accordance with Section 28.6.2, below.

These provisions allow rather easy certification of plant opera-tions, maintenance, test, and engineering personnel.

In lieu of meeting the requirements of CP-189, VT-3 visualexamination personnel may be certified by meeting the followingrequirements:

(1) At least 40 hr. of plant experience. (2) At least 8 hr. of training in the Section XI VT-3 visual exam-

ination requirements and plant-specific VT-3 visual exami-nation procedures.

(3) A vision test in accordance with Section 28.6.2, below.

These provisions allow rather easy certification of plant mainte-nance personnel. However, for either of the two preceding certifi-cation requirement options, the Owner’s written practice mustdescribe how these requirements will be met.

Since the 1989 Addenda, Section XI has required that ultrasonicexamination (UT) personnel be qualified and certified by perfor-mance demonstration, in accordance with Mandatory AppendixVIII. This appendix provides different qualification for require-ments for each type of base material and weld configuration. Therequirements have been constantly changing since 1989, as theCommittee has been grappling with the appropriate means ofqualification for examination of different configurations or combi-nations of configurations. These provisions require personnel todemonstrate their ability to accurately detect and size flaws byultrasonic examination.

28.6.2 IWA-2320–IWA-2380: QualificationExaminations, Experience, andResponsibilities

All NDE personnel are required to have annual vision examina-tions to demonstrate natural or corrected near-distance acuityequivalent to 20/25 or greater Snellen fraction. In addition, per-sonnel performing VT-2 or VT-3 visual examinations, both ofwhich may require examination from somewhat greater distancesthan VT-1 visual examination, are required to demonstrate natural

or corrected far-distance acuity of 20/30 or greater Snellenfraction. A recent revision permits an optometrist, ophthalmolo-gist, or other heath care professional to administer the vision acu-ity examinations. NDE personnel must also demonstrate the abilityto distinguish the colors applicable to the NDE methods for whichthey are certified.

28.6.3 Level III NDE Personnel Level III NDE personnel are required to demonstrate, by

written examination, a general knowledge of NDE methodologyand of materials, products, and fabrication technology. Also bywritten examination, they must demonstrate expertise in apply-ing the fundamentals and principles of the specific method forwhich certified; in preparing procedures; in applying techniques,codes, standards, and specifications for the method, equipment,techniques, procedures, and administration of the Owner’s writ-ten practices; and applying NDE requirements of Section XI andreferenced standards, including applicable acceptance standards.Credit for a specific portion of these requirements may be satis-fied by an ASNT Level III Certificate for the method used. TheLevel III candidate must demonstrate the ability to apply thisknowledge by preparing a procedure for a relevant examinationand, in addition, is responsible for the training and qualificationof Levels I and II personnel. The Level III is also permitted towrite procedures, perform examinations, and interpret theresults of examinations. Because of the many requirements, theLevel III candidate must have either a 4-yr. college engineeringor other science degree plus 1-yr. of experience in the NDEmethod or a 2-yr. college engineering or other science degreeplus two years of experience in the NDE method. In lieu ofthese educational requirements, the Level III candidate mayhave 4-yr. of experience in the NDE method. Level II and IIINDE personnel are required to perform “annual practice,” whichincludes annual evaluation of actual samples or prerecorded data“containing flaws similar to those encountered during inserviceexamination.” The purpose of annual practice is to maintainskills in flaw evaluation, a job function of Level II and IIIpersonnel.

28.6.4 Level II NDE Personnel Level II NDE personnel are required to demonstrate, by written

examination, a knowledge or expertise of the materials, products,and fabrication technology relevant to the products to be exam-ined; the fundamentals and principles of the specific method forwhich he or she is certified; the application of the techniques to beused; the codes, standards, and specifications of the Owner’s writ-ten practices; the equipment, techniques, and procedures to beused; and the NDE requirements of Section XI and referencedstandards of the method for which he or she is certified, includingany applicable acceptance standards. The NDE Level II candidatemust also demonstrate the ability to apply this knowledge by con-ducting a demonstration examination. The Level II is permitted,as provided by the Owner’s written practice, to write procedures,perform examinations, and interpret the results of examinations.Level II and III NDE personnel are required to perform “annualpractice,” which includes annual evaluation of actual samples orprerecorded data “containing flaws similar to those encounteredduring inservice examination.” The purpose of annual practice isto maintain skills in flaw evaluation, a job function of Level II andIII personnel.

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 6

Page 7: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 7

28.6.5 Level I NDE Personnel Level I NDE personnel are permitted only to conduct examina-

tions in accordance with approved written procedures under thedirection of Levels II or III personnel. The Level I examiner is notpermitted to interpret the results of examinations.

28.6.6 IWA-2350: Limited Certification Any of the aforementioned personnel may be qualified for a lim-

ited scope of the activities discussed in the preceding paragraphs.Such certification may include fewer training hours and examina-tion questions, as well as a limited demonstration. In addition, therequired experience may be reduced by a corresponding amount.For example, some individuals are qualified to only interpret radi-ographic film rather than setting up or conducting the radiographicexamination. This qualification is commonly known as a Level II-Rcertification. (The “R” denotes “restricted.”) The restrictions andlimitations must be defined in the Owner’s written practice anddocumented in the individual’s certification record.

28.7 MANDATORY APPENDIX VII:QUALIFICATION OFNONDESTRUCTIVE EXAMINATIONPERSONNEL FOR UT

Appendix VII provides specific requirements that supplementthe requirements of IWA-2300 for training and qualification of UTpersonnel. For this method, Appendix VII introduces two additionalNDE Levels: the Trainee and the NDE Instructor. No requirementsare provided for the Trainee, but the NDE Instructor must satisfythe Level III basic and method requirements and must have eithera teacher’s or vocational instructor’s certificate issued by a govern-ment agency, or else 40 hr. instruction in training and teachingtechniques. Training must be conducted by or under the directionof an NDE Instructor. Appendix VII requires more training andexperience than does IWA-2300 for other NDE methods; detailedrequirements are provided for the content of training courses andalso for the content and conduct of qualification examinations. Inaddition, Appendix VII requires at least eight hours each year ofpracticing UT examinations by scanning flaws and geometricreflectors. A revision in the 2002 Addenda clarified that, since the1992 Addenda, IWA-2380 required compliance with the require-ments of VII-4140 for NDE Instructors for all NDE methods.Because Appendix VII applies only to ultrasonic examination, itwas not clear that the requirements applicable to NDE Instructorswere generic. In the 2002 Addenda, to clarify this intent, the provi-sions of VII-4140 were moved into IWA-2380.

28.8 IWA-2400: INSPECTION PROGRAM

28.8.1 IWA-2410: Application of Code Edition andAddenda

The Code Edition and Addenda for preservice inspection andfor initial and successive inservice inspection intervals arerequired to be selected in accordance with 10CFR50, Section50.55a, Codes and Standards. This subsubarticle references therules of 10CFR50.55a to avoid potential conflict with the U.S.federal regulations. For plants outside of the United States, theserequirements are often applied, but they may be superseded bylocal regulations.

28.8.2 Preservice Inspection 10CFR50.55a(g) requires preservice examinations of Class 1,

2, and 3 components and supports in a plant with a constructionpermit issued by the USNRC on or after January 1, 1971. Theapplicable Edition and Addenda of Section XI for a plant with aconstruction permit issued before July 1, 1974, is the Edition andAddenda incorporated by reference in 10CFR50.55a(b) 6 mo.before the construction permit’s issuance. For a plant with a con-struction permit issued on or after July 1, 1974, the applicableEdition and Addenda of Section XI is the same as the Edition andAddenda of the ASME Boiler and Pressure Vessel Code (usuallySection III) used for construction of the component.

Alternatively, preservice examinations for all components andsupports may meet all or portions of later Editions or Addenda ofSection XI, as permitted by 10CFR50.55a(b) or as authorized bythe director of the USNRC’s Office of Nuclear Reactor Regulation.

28.8.3 Inservice Inspection For all plants regardless of the construction permit date, inser-

vice examinations and pressure tests for the first 120 mo. (10 yr.)must comply with the latest Edition and Addenda of Section XIincorporated by reference in 10CFR50.55a(b) on the date 12 mo.before the date of issuance of the operating license. For all subse-quent 10 yr. intervals, inservice examinations and pressure testsmust comply with the latest Edition and Addenda of Section XIincorporated by reference in 10CFR50.55a(b) on the date 12 mo.before the start of the particular interval.

Alternatively, inservice examinations and pressure tests for allcomponents and supports may meet all or portions of laterEditions or Addenda of Section XI, as permitted by10CFR50.55a(b) or as authorized by the director of the USNRC’sOffice of Nuclear Reactor Regulation. When parts of laterEditions and Addenda are used, all related requirements of theparticular Editions and Addenda must be met.

28.8.4 Related Requirements No clear explanation exists in Section XI and in any of the

USNRC’s documents that explains how to determine the meaningof the term all related requirements. Because of the lack of specificguidance, various interpretations have arisen. The least conserva-tive interpretation allows selection of a single provision, which insome cases can result in a significant reduction in safety below thatintended by the Committee. An example is applying B31.7Nuclear Power Piping Class I, or 1971 or later Section III Class 1,design requirements, while using the original B31.1 Power Pipingfabrication and installation requirements, for a modification. Thereduced design factors in the B31.7 Class I or Section III Class 1requirements were intended to be used only with the increased fab-rication and examination requirements of NB-4000 and NB-5000;adopting the later provisions only for design will cause a reductionin the overall technical requirements for the piping system.Although there are no other examples of this magnitude, a fewexamples exist in which the use of some later provisions can per-mit reduction in the design margins intended by the Committee.For example, the B1 and C1 stress indices (see Section III,NB/NC/ND-3600) were both revised in a single action of theCommittee: the pipe factor was reduced and the weld factor wasincreased to compensate (or vice versa). In this case, the increasedweld factor must be used whenever the reduced pipe factor is used;otherwise, a reduction in the intended design factor will result.

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 7

Page 8: Asme Companion

8 • Chapter 28

Another means of adopting later Editions or Addenda is use of allportions of any subsections applicable to a certain activity, such asNB-3600 for piping design or NB-4000 and NB-5000 for installa-tion of a valve. This approach results in unnecessary con-servatism,except for the preceding example of B31.7 Class I or Section IIIClass 1 design with other fabrication or installation requirements.

The following guidance ensures that a consistent set of require-ments will be used and that the design margins intended by theASME Boiler and Pressure Vessel Code will be maintained. Thisapproach has been used successfully by many organizations forover 25 yr.

In the early 1970s, the ASME Boiler and Pressure VesselCommittee directed the Subcommittee on Nuclear Power (alsocalled Subcommittee III) to add provisions to Section III [seeNCA-1140(b) for additional information] to allow users workingto later Editions and Addenda to use provisions of a Code Caselong after its incorporation and annulment. Subcommittee IIIchose the phrase all related requirements to describe the set ofprovisions that were moved from the Code Case into the body ofSection III concurrent with annulment of the Case. The relatedrequirements are considered to be all of those provisions added bythe Committee in a single voted action, such as copying the CodeCase provisions into the Code. Conservatively, the provisionsshould also include all of the requirements of the same Editionand Addenda in the paragraphs that the Committee revised bysubject action. Thus, using the related provisions is in principleidentical to using the provisions of the Code Case to replace theprovisions of the Code of record.

The paragraphs that are affected by any Committee action canbe obtained from several sources—from the ASME (for about fiveyears after approval); from the ASME-published MechanicalEngineering (before mid-2000); and from some proprietarysources, such as RA-Search®, which is developed and sold byReedy Engineering (see http://www.reedyeng.com).

28.9 IWA-2420: INSPECTION PLANS AND SCHEDULES

Before the start of each inspection interval, the Owner isrequired to prepare plans and schedules describing how and whenthe examinations and tests required by Section XI will be per-formed. The plans are required to identify enough information toensure that all of the applicable requirements will be met. Thisincludes the following:

(1) The Edition and Addenda of Section XI that applies to therequired examinations and tests.

(2) The classification of the component and the boundaries ofsystem classifications.

(3) The identification of the components subject to examinationand testing.

(4) The Code requirements by Category and Item Number foreach component and the examination or test to be per-formed.

(5) The Code requirements by Category and Item Number foreach component that are not being satisfied by the examina-tions and tests.

(6) Code Cases proposed for use and the extent of theirapplication.

The ANII is required to review the inspection plan before thestart of each inspection interval [see IWA-2110(a) for additional

information]. The Owner is required to submit these plans to theenforcement and regulatory authorities having jurisdiction at theplant site [see IWA-1400(c) for additional information]. For mostU.S. plants, the plans are required to be submitted only to theUSNRC, but for other plants, the plans are required to be submit-ted to various state enforcement agencies. Outside of the UnitedStates, submittal to a federal regulatory agency is usually required.

28.10 IWA-2430: INSPECTION INTERVALS

The specified examinations and tests are required to be per-formed during each 10-yr. interval for the life of the power plant.Section XI provides two schedules for performing these examina-tions. The length of time of each of these intervals is quite differ-ent. The program selected for each Class of components orsupports does need not to be the same.

The Inspection Program is based on relatively uniform degra-dation over a potentially unlimited life. The inspection intervalsare of uniform duration, of 10 yr. each, for the operating life ofthe plant.

The requirements permit adjustments to the duration of theinspection intervals, within prescribed limits. Each interval maybe reduced or extended by as much as 1 yr. from the normal 10 yr.,if the reduction or extension is within 1 yr. of the original patternof 10-year intervals. These adjustments are normally made toenable the end of the interval coincide with an outage so that anyremaining examinations for that interval may be completed ontime. Also, they allow beginning the examinations of the nextinterval during the same outage in which examinations are per-formed to complete the previous interval.

It is important to note that when examinations are performedduring an outage that overlaps two intervals, each examinationperformed may be credited to only one of the two intervals; dou-ble credit for any one examination is not permitted. A simpleexample is as follows: Suppose a plant started its commercialoperation on January 1, 1980. The second inspection intervalwould thus begin on January 1, 1990. With the 1-yr. tolerance onthat date, the second interval could begin any time betweenJanuary 1, 1989 and January 1, 1991. Now assume that the firstinterval was extended 6 mo. to coincide with a refueling outageand the second interval began on July 1, 1990. The third intervalwould then have to begin between July 1, 1999 (9 yr. from theinterval start date) and January 1, 2001 (20 yr. after the date ofcommercial operation, but only yr. after the second intervalstart date). Note that the tolerance on the 10-yr. interval length hasbeen reduced by the 6-mo. extension of the first interval.

To provide additional flexibility, for plants that are out ofservice continuously for 6 mo. or more, the inspection intervalduring which the outage occurs may be extended for a periodequivalent to the outage. In this case, the original pattern of inter-vals is extended accordingly for successive intervals. In essence,for this case, future interval transition dates are based on a reviseddate of commercial operation, after adding the length of theextended outage. Doing so establishes a new pattern of intervalsto which the 1-yr. reduction or extension may be applied.

Now, in the previous example, suppose that the plant was out ofoperation for 1 yr. at some point during the second interval. In thiscase, the second interval could be extended by an additional 12 mo.Assuming that the Owner decides to take advantage of the exten-sion, the third interval would begin between July 1, 2000 (10 yr.from the interval start date) and january 1, 2002 (21 yr. after

10 12

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 8

Page 9: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 9

the date of commercial operation, and years after the secondinterval start date). In this case, the fourth interval would beginwithin 1 yr. of January 1, 2011, and no more than 9 nor less than11 yr. following the beginning of the third interval.

The provisions for extension and reduction of the intervallength also apply to that portion of an interval defined as a period.This subject is addressed further in Section 28.24, which discussesthe IWB/IWC/IWD/IWE/IWF/IWL-2400 Inspection Schedule.

The inspection intervals for new items installed by repair/replacement activities are to coincide with remaining intervals (asthey were previously scheduled) rather than by setting up differ-ent intervals for the new items, as exemplified by InterpretationXI-1-86-54.

Question (1): Is it a requirement of Section XI, IWA-2400,IWB-2400, IWC-2400, or IWD-2400 that the extension ofinspection intervals by as much as one year to be concurrentwith plant outages (as allowed by IWA-2400) be applied onlyduring the last one-third of the interval?

Reply (1): No.

Question (2): May the extensions in inspection intervals inIWA-2400 for both out-of-service and plant outage conditionsbe applied serially?

Reply (2): Yes.

28.11 IWA-2440: APPLICATION OF CODE CASES

28.11.1 Section XI Code Cases Section XI contains specific provisions for the use of Section XI

Code Cases, which were adopted from the USNRC RegulatoryGuide 1.147, Inservice Inspection Code Case Acceptability, ASMESection XI, Division 1. The Regulatory Guide provides USNRCgeneric acceptance of Section XI Code Cases that the USNRC hasfound acceptable. The USNRC reviews all Code Cases publishedby the ASME that provide alternatives to Section III or Section XIrequirements. Following the review and evaluation of the Cases, theUSNRC decides whether to allow their use and whether to imposeany additional limitations on their use. The Regulatory Guide docu-ments this acceptance and imposes any such limitations.

10CFR50.55a explains that the Cases listed in RegulatoryGuide 1.147 have been determined by the USNRC to be suitablefor use. It also states that additional Cases not listed in theRegulatory Guide may be used when they are authorized by theUSNRC’s director of the Office of Nuclear Reactor Regulationupon request pursuant to Section 10CFR50.55a(a)(3). This provi-sion is used primarily for obtaining acceptance of Cases publishedafter the most recent revision of Regulatory Guide 1.147, whichmay be as often as annually or as infrequently as every 5 yr. Thisprovision also allows use of Code Cases to be authorized by theUSNRC as an equivalent alternative to the mandatory Coderequirements rather than authorized as “relief” from the existingrequirements. It is important to note that 10CFR50.55a(a)(3) isintended specifically to allow use of equivalent alternatives, suchas Code Cases or later Code Editions and Addenda, whereas10CFR50.55(g)(6)(i) is intended to allow “relief” simply by elim-inating the need to meet specific impractical Code requirements.

The provisions in IWA-2441 and Regulatory Guide 1.147 wererevised in the 2008 Addenda to be more thorough in their cover-age of Section XI Code Cases. Section XI used to address only

1112

Code Cases used “during a preservice or inservice inspection”;Regulatory Guide 1.147, similarly addresses only Code Casesused “for application in the inservice inspection of componentsand their supports,” and “during an inspection interval or . . . fora preservice inspection.” The significance of these words is thatCode Cases used in repair/replacement activities were notaddressed either by IWA-2440 or by the Regulatory Guide.These requirements for use of Code Cases were limited to preser-vice and inservice inspection and did not include repair/replace-ment activities, probably because 10CFR50.55a has never clearlyaddressed requirements for repair, replacement, or modification.It is not clear why the requirements of IWA-4000 (and IWA-7000in earlier Editions and Addenda) have been consistently applied,but they are assumed to be mandatory, both by the USNRC andthe Owners.

Nonetheless, the provisions in IWA-2440 used to address onlyCode Cases for preservice and inservice inspection, and notthose for repair/replacement activities. This has changed with the2008 Addenda, with new requirements for all Code Cases to beused in performing repair/replacement activities now in IWA-4190. These requirements are similar to those of IWA-2440.Additional requirements for Code Cases for repair/replacementactivities can be found in IWA-4150, Repair/ReplacementProgram and Plan. Their use is also documented on Form NIS-2,found in Appendix II. Therefore, the following requirements foruse of Code Cases for preservice and inservice inspection arealso generally applicable to repair/replacement activities. Theyare also considered applicable to evaluation of the results of non-destructive examinations.

Code Cases for preservice and inservice inspection must beidentified in the inspection plan (the Repair/Replacement Plan forrepair/replacement activities). The Cases must be applicable tothe Edition and Addenda of Section XI specified in the inspectionplan. The applicability can be easily determined by reviewing theApplicability Index for Section XI Cases, which is published inthe ASME Code Cases: Nuclear Components. This index lists allof the currently available Section XI Code Cases as well as manythat have been superseded or annulled. It shows the range ofSection XI Editions and Addenda to which each Case is applica-ble and may be used. The applicability range is typically limitedby revisions to Section XI, such as incorporation of the provisionsof a Case, or by changes in the numbering of paragraphs refer-enced by the Case.

Code Cases must be in effect at the time the inspection plan isfiled with the enforcement and regulatory authorities, whichmeans that the Case is included in the latest Edition of the ASMECode Cases: Nuclear Components, including all supplementsissued before the filing date. This provision is intended to guardagainst use of obsolete Cases and those that are inconsistent withthe requirements of the selected Section XI Edition and Addenda.This provision has been modified to address the issue of theUSNRC lagging significantly behind the ASME in its endorse-ment of Code Case revisions published by the ASME.Occasionally an Owner would choose to use the latest revision ofa Code Case endorsed by the USNRC, even though it was not thelatest published by the ASME. This caused a de facto failure tostrictly comply with IWA-2440. The new provisions allow theOwner to use superseded Code Cases, if the selected revisions arethe latest endorsed by the regulatory and enforcement authorities,even if they are not the latest published by the ASME.

Code Cases issued by the ASME after the inspection plan is filedmay be added to the plan, subject to acceptance by the enforcement

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 9

Page 10: Asme Companion

10 • Chapter 28

and regulatory authorities as described in the preceding paragraphs.When a Code Case is annulled or is superseded by revision, use ofthe Case revision listed in the inspection plan may continue for theduration of the inspection plan (i.e., the 10-yr. interval). At the startof the next interval, the desired provisions will likely be included inthe text of the Edition and Addenda selected for use in that andfuture intervals.

28.11.2 Code Cases for Other Sections Requirements have not been developed to address use of Code

Cases of other Code Sections, because they are not needed. CodeCases of Section III are addressed in IWA-4150, Repair/Replacement Program and Plan, and are addressed by USNRCRegulatory Guide 1.84. Code Cases for ASME B31.1 and forASME Boiler and Pressure Vessel Code Sections II, V, VIII, andIX are in no way controlled or limited by the USNRC; they arenot addressed by 10CFR50.55a or the USNRC RegulatoryGuides. Because the USNRC does not review and endorse theseCode Sections (other than Section III), nor their respective CodeCases, NRC permission to use such Cases is unnecessary.Therefore, any of these Code Cases (other than Section III) maybe used for preservice or inservice inspection or repair/replacement activities, without USNRC approval.

28.12 IWA-2500: EXTENT OF EXAMINATION

When the component or system examination requirements ofIWB-2500 through IWL-2500 specify examination of welds, theextent of the examination includes only welds joining items. Theexamination requirements do not include welds correcting flawsin base material, except for repair welds in the reactor vesselbelt-line region with a depth that exceeds 10% of the nominalvessel wall-thickness (see Table IWB-2500-1, ExaminationCategory B-J). Wear-resistant hardsurfacing overlays and coreclosure welds in castings are not required to be examined.Corrosion-resistant overlay cladding is not required to be exam-ined, except in conjunction with examinations of full-penetrationwelded nozzles in Class 1 vessels (see Table IWB-2500-1,Examination Category B-J [given here as Table 28.1], and Fig.IWB-2500-7).

28.13 IWA-2600: WELD REFERENCESYSTEM

28.13.1 IWA-2610: General To ensure reproducibility of examinations, the Owner must

establish a reference system for all welds and areas subject to sur-face or volumetric examination, including a system of referencepoints. This system must permit the identification of each weld,the location of each weld centerline, and the designation of regu-lar intervals along the length of the weld; for piping, the systemmust permit location of the search unit along the weld seam anddetermination of its position in reference to the weld centerline.By ensuring reproducibility of examinations, the Owner can com-pare the extent of identified flaws or indications with the extent ofthe same flaws or indications at the time of previous examina-tions. Low-stress stamps, vibratooling, or a combination of bothmay be used to permanently identify each weld, although perma-nent markings are not required. Section XI provides some recom-mended systems that may be used to satisfy these requirements.

28.14 SUBSECTIONS IWB/IWC/IWD/IWE/IWF/IWL: REQUIREMENTS FORCLASS 1, 2, 3, MC, AND CCCOMPONENTS AND SUPPORTS

Subsections IWB/IWC/IWD/IWE/IWF/IWL-1000 and IWB/IWC/IWD/IWE/IWF/IWL-2000 provide examination require-ments for Class 1, 2, 3, MC, and CC pressure-retaining compo-nents and welded attachments, as well as their supports.(Subsection IWG, Examination of Core Support Structures, is stillin the early stage of preparation.)

28.15 EXEMPTIONS FROM THEEXAMINATION REQUIREMENTS

The following components or parts of components are exemptedfrom the volumetric, surface, and VT-1 and VT-3 visual examina-tion requirements of IWB/IWC/IWD/IWE/IWF/IWL-2000. Theseexemptions do not apply to VT-2 visual examinations performedduring conduct of pressure testing.

28.15.1 Class 1 Components Exempt fromExamination

(a) Components that are connected to the reactor coolant sys-tem, that are part of the reactor coolant pressure boundary, andthat are of such a size and shape that, upon postulated rupture,the resulting flow of coolant from the reactor coolant systemunder normal plant operating conditions is within the capacity ofmakeup systems that are operable from on-site emergency powerare exempt from examination. Emergency core–cooling systemsare excluded from the calculation of makeup capacity becausethey do not operate during normal plant operation. InterpretationXI-1-92-45 states,

Question: Is it the intent of Section XI, IWB-1220(a) that emergency core–cooling systems be excluded from thecalculation of makeup capacity?

Reply: Yes.

(b) Other exemptions are piping NPS 1 and smaller, except forsteam-generator tubing, and pumps, valves, vessels, and tanks inpiping NPS 1 and smaller. To satisfy this exemption criterion, acomponent must have a cumulative inlet and a cumulative outletpipe cross-sectional area neither of which exceeds the nominalOD cross-sectional area of NPS 1 pipe. (NPS is a dimensionlessdesignator of nominal pipe size that is closely related to the diam-eter of the pipe in inches.)

(c) Another exemption is reactor vessel head connections andassociated piping, NPS 2 and smaller, made inaccessible bycontrol-rod-drive penetrations.

28.15.2 Class 2 Components Exempt from Examination

(a) Piping, vessels, pumps, and valves and their connections inpiping NPS 4 and smaller in residual heat removal (RHR), emer-gency core–cooling (ECC), and containment heat removal (CHR)systems, or portions of systems, other than high-pressure safety-injection systems, are exempt from examination. Piping, vessels,pumps, and valves and their connections in piping NPS 4 andsmaller in systems or portions of systems other than RHR, ECC,

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 10

Page 11: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 11

and CHR systems, other than auxiliary feed water systems, arealso exempted.

(b) Also exempted are piping, vessels, pumps, and valves andtheir connections in piping NPS and smaller in high-pressuresafety-injection systems in RHR, ECC, or CHR systems, and inauxiliary feedwater systems. (This piping is defined as having acumulative inlet and a cumulative outlet pipe cross-sectional areaneither of which exceeds the nominal OD cross-sectional area ofthe designated size.)

(c) Vessels, piping, pumps, valves, other components, andcomponent connections of any size in statically pressurized, pas-sive (i.e., no pumps) safety-injection systems of pressurized waterreactor plants are also exempted. These systems are typicallyassociated with the accumulator tank, safety-injection tank, orcore-flooding tank.

(d) Also exempted are piping, vessels, pumps, and valvesand their connections of any size in systems or portions of sys-tems that operate (when the system function is required) at apressure not exceeding 275 psig and at a temperature notexceeding 200°F in systems or portions of systems other thanRHR, ECC, and CHR.

(e) Piping and other components of any size beyond the lastshutoff valve in open ended portions of systems that do not con-tain water during normal plant operating conditions are alsoexempt from examination.

28.15.3 Class 3 Exemptions Class 3 systems that do not support one of the following six

functions are exempt from examination:

• reactor shutdown • emergency core–cooling • containment heat removal • atmosphere cleanup • reactor residual heat removal • residual heat removal from spent fuel storage pool

In addition, the following Class 3 components are exempt fromexamination, even if they do support one of the six functions inthe preceding list.

(a) Piping, vessels, pumps, and valves and their connections inpiping NPS 4 and smaller.

(b) Components that operate at a pressure of 275 psig or lessand at a temperature of 200�F or less in systems (or portions ofsystems) with a function that is not required in support of reactorresidual heat removal, containment heat removal, and emergencycore cooling.

28.16 CLASS 1, 2, AND 3 COMPONENTS AND THEIR SUPPORTS EXEMPTFROM EXAMINATION

In addition to the aforementioned exemptions, welds or portionsof welds that are inaccessible from being encased in concrete,buried underground, located inside a penetration, or encapsulatedby guard pipe are also exempt from examination. Although thisexemption was added recently, most such welds have been exemptedby relief granted by the USNRC under 10CFR50.55(g)(6)(i). Inmany such cases, the USNRC requires that other welds, usuallynear the ones being exempted, be examined as substitutes.

112

28.17 CLASS MC COMPONENTS ANDLINERS OF CLASS CC COMPONENTSEXEMPT FROM EXAMINATION

The following components (or parts of components) are exemptfrom the examination requirements of IWE-2000.

(a) Vessels, parts, and appurtenances that are outside theboundaries of the containment as defined in the DesignSpecifications. (This reference to Design Specifications is anotherholdover from the preparation of Section XI by Subcommittee III.The term Design Specifications includes other similar construc-tion specifications for vessels that were not constructed inaccordance with Section III requirements; such Specifications areusually generically called Owner’s Specifications in Section XI.)

(b) Embedded or inaccessible portions of containment vessels,parts, and appurtenances that meet the requirements of the origi-nal Construction Code.

(c) Portions of containment vessels, parts, and appurtenancesthat become embedded or inaccessible as a result of vesselrepair/replacement activities if the design restrictions and exami-nation requirements of IWE-1232 and IWE-5220 are met.

(d ) Piping, pumps, and valves that are part of the containmentsystem or that penetrate or are otherwise attached to the contain-ment vessel. These components are not considered part of thecontainment vessel; they are usually portions of process pipingsystems that penetrate the containment vessel. (Containment pen-etrations that are not part of process piping systems do not fallinto this category; these are treated as part of the containmentvessel.) These components or portions of systems are examined inaccordance with Class 1 or 2 requirements, as appropriate to theclassification defined in the Owner’s Specifications. The systemsalso include those that are outside of the Section XI jurisdictionalboundaries, such as the containment air sampling or instrumentair systems. In recent years, however, the USNRC has requiredthat the portions of these systems that penetrate the containmentvessel between the inboard and outboard containment isolationvalves (all forming a portion of the containment boundary) beexamined in accordance with Class 1 or 2 requirements. Thus,they are constructed and examined in a manner that provides anequivalent level of quality to that of the containment vessel.

IWE-1231 requires that certain portions of Class MC contain-ment vessels, parts, and appurtenances, as well as Class CCmetallic shell and penetration liners remain accessible for exami-nation (from least one side of the vessel) for the life of the plant.These portions include all openings and penetrations; all structur-al discontinuities; 80% of the pressure-retaining boundary otherthan attachments, structural reinforcement, and areas made inac-cessible during construction; and surfaces subject to accelerateddegradation, for which augmented examination is required byIWE-1240.

IWE-1232 provides criteria for allowing portions of Class MCcontainment vessels, parts, and appurtenances and Class CC con-tainment liners to be embedded in concrete or otherwise madeinaccessible during construction or repair/replacement activities.These provisions require the following:

(1) No openings or penetrations may be made inaccessible. (2) Inaccessible welded joints must be double-butt-welded,

fully radiographed, and leak-tested. (3) The containment vessel must be leak-tested following com

pletion of construction (or completion of repair/replacementactivities on all such inaccessible portions).

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 11

Page 12: Asme Companion

12 • Chapter 28

28.18 PORTIONS OF REINFORCEDCONCRETE CONTAINMENT VESSELSAND THEIR POSTTENSIONINGSYSTEMS EXEMPT FROMEXAMINATION

The following items are exempt from the examination require-ments of IWL-2000:

(1) Tendon-end anchorages that are inaccessible, subject toselection of a replacement sample in accordance with therequirements of IWL-2521.1.

(2) Portions of the concrete surface that are covered by the liner,foundation material, or backfill, or that are otherwiseobstructed by adjacent structures, components, parts, orappurtenances.

28.19 IWF-1300: COMPONENT SUPPORTEXAMINATION BOUNDARIES

Subsection IWF uses the terms integral support and noninte-gral support. An integral support is one that is cast or forged inte-grally with the component being supported, whereas a nonintegralsupport is one that is attached to the component by a mechanicalconnection, such as a pipe clamp. The mechanical connection of anonintegral support is the attachment of the support rod to theclamp, by pins or bolts. When this mechanical connection isburied within the component insulation, the support examinationboundary may extend from the surface of the component insula-tion to the building structure, if the support carries the weight ofthe component or serves as a structural restraint in compression.Therefore, the insulation does not need to be removed to exposethe attachment of the support rod to the clamp, whenever the sup-port carries the weight of the component or serves as a structuralrestraint in compression. The examination of those portions of thesupport that are visible outside the insulation surface is expectedto provide adequate information regarding the physical conditionof those portions of the support that are covered with insulation.

Subsection IWF also uses the term intervening element, whichis defined as an item whose primary function is not to support acomponent; component support may be a secondary function. Anexample is a portion of a diesel generator providing support to asafety-related cooling line for the generator lube oil. The exami-nation boundary includes the attachment portion of the supportclamp to the diesel generator, but it does not include the balanceof the diesel generator.

28.20 IWB-2000: EXAMINATION AND INSPECTION

Preservice examination of all Class 1 components is requiredbefore service, with limited exemptions, and provides a baselinefor future inservice examinations. The results of the inserviceexaminations are compared with the preservice baseline to helpevaluate the effects of service-induced degradation. The preserviceexamination is extended to essentially 100% of all Class 1 weldsnot exempted by IWB-1220. Pressure testing and visual examina-tion of internal surfaces of pumps and valves are not required to beperformed as a preservice examination. In addition, only theperipheral control-rod drive housings are required to be examined.

For Class 2 components, only those welds, areas, or partsselected for inservice examination are required to have a preservice

examination performed. Other welds, areas, or parts of Class 2components are not required to have a preservice examination.The only reason a preservice examination is sometimes per-formed on any other welds, areas, or parts of Class 2 componentsis to establish a baseline for possible future use if those particularcomponents are required to be examined later. This requirementmay be caused either by changes in the Inservice Inspection (ISI)Program or by being selected as a part of sample expansionrequired as a result of defect identification during inserviceinspection of those components initially selected for examination.

For Class 3 components, all welded attachments subject toexamination during any inspection interval are required to beexamined before initial plant startup.

For Class 1, 2, 3, MC, and CC component supports, all exami-nations required to be performed during any inspection intervalmust be done before initial plant startup.

For Class MC vessels and liners of Class CC vessels, all areassubject to examination during any inspection interval are requiredto be examined before initial plant startup. If protective coatingsare to be applied to any of these items, the examinations must beperformed after application of the coatings. For concrete contain-ment vessels, all accessible surfaces are examined before initialplant startup; for unbonded post-tensioning systems, all tests andexaminations applicable to any inspection interval are required tobe performed before initial plant startup.

The treatment of containment vessels presents a unique situation,because until 1996, implementation of Subsections IWE and IWLwas not mandated by the USNRC. Therefore, the baseline exami-nations required by Section XI have not been performed on anyU.S. plant; consequently, the USNRC has mandated that the first-period examinations be performed on an expedited schedule toserve as baseline examinations for the future. For U.S. plants, theseexaminations were required to be conducted by September 2001.

28.21 COMBINING PRESERVICEEXAMINATIONS WITHCONSTRUCTION CODE SHOP AND FIELD EXAMINATIONS

For all Classes of construction, shop and field examinationsmay be combined with the preservice examinations, if theexamination methods and personnel satisfy the requirements ofboth the applicable Construction Code and IWA-2000, and if themethods used are equivalent to those that will be used for subse-quent inservice examinations. For vessels, the examination mustbe performed after completion of any hydrostatic test or structuralintegrity test (for concrete vessels and unbonded post-tensioningsystems) required by the Construction Code.

Section XI contains very few requirements applicable to steam-generator tubing. The requirements largely default to the plantTechnical Specifications.

28.22 IWE-2300: VISUAL EXAMINATION,PERSONNEL QUALIFICATION, AND THE RESPONSIBLE INDIVIDUAL

28.22.1 IWE-2310: Visual Examinations These new visual examination requirements, added in the 1998

Edition, give the Owner considerable latitude in defining require-ments for qualification of visual examination personnel, performanceof visual examinations, and evaluation of visual examination results.

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 12

Page 13: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 13

Visual examinations fall into two categories: general visualexamination and detailed visual examination. The general visualexamination is used to assess the general condition of contain-ment surfaces. The detailed visual examination is used to evaluatethe condition of surfaces that require augmented examination inaccordance with IWE-1241 and suspect containment surfacesdetected by general visual examination. In addition, it is used todetermine the magnitude of any deterioration or distress of thesesurfaces, and to evaluate the condition of areas affected byrepair/replacement activities. The detailed visual examinationincludes examination of painted or coated areas for evidence offlaking, blistering, peeling, discoloration, and other signs of dis-tress, and uncoated areas for evidence of cracking, discoloration,wear, pitting, excessive corrosion, gouges, surface discontinuities,dents, and other signs of surface irregularities.

28.22.2 IWE-2320: The Responsible Individual Conduct of all examinations and evaluation of examination

results is the responsibility of a person called the ResponsibleIndividual. This person must be knowledgeable in the require-ments of design, inservice inspection, and testing of Class MCvessels and metallic liners of Class CC concrete vessels. TheResponsible Individual must develop plans and procedures forexaminations; must supervise the instruction, training, andapproval of visual examination personnel; and must perform ordirect visual examinations and evaluation of examinationresults.

28.22.3 IWE-2330: Personnel Qualification Another change in the 1998 Edition gave the Owner the

responsibility for defining qualification requirements for per-sonnel performing visual examinations. These examinations mustbe performed by individuals with visual acuity sufficient to detectevidence of degradation. However, the USNRC has mandated thatpersonnel performing detailed and general visual examinations bequalified and certified as required for VT-1 and VT-3 personnelrespectively, in accordance with IWA-2210. In response to theseUSNRC limitations, the 2007 Addenda replaced the Owner-defined qualification requirements for concrete containmentexamination personnel with specific qualification requirements,including both experience and training requirements.

28.23 IWL-2300: VISUAL EXAMINATION,PERSONNEL QUALIFICATION, AND THE RESPONSIBLE ENGINEER

28.23.1 IWL-2310: Visual Examination and Personnel Qualification

These new visual examination requirements, added in the 1999Addenda, give the Owner considerable latitude in definingrequirements for qualification of visual examination personnel,performance of visual examinations, and evaluation of visualexamination results. Visual examinations fall into two categories:general visual examination and detailed visual examination.

The general visual examination is used to assess the generalcondition of containment surfaces. This examination is performedin sufficient detail to identify areas of concrete deterioration anddistress, such as those defined in ACI 201.1.

The detailed visual examination is used to determine the mag-nitude of deterioration and distress of suspect concrete surfacesidentified by the general visual examination; the condition and

any deterioration of concrete surfaces at tendon anchorage areas;the condition of tendon wires or strands and anchorage hardware;and the condition of concrete surfaces affected by repair/replace-ment activities.

All visual examinations are performed by individuals withvisual acuity sufficient to detect evidence of degradation.Qualification requirements for examination personnel andrequirements for visual examination of tendon anchorage hard-ware, wires, or strands are at the discretion of the Owner.

In response to USNRC limitations in 10CFR50.55a, the 2007Addenda replaced the Owner-defined qualification requirementsfor concrete containment examination personnel with specificqualification requirements, including both experience and trainingrequirements.

28.23.2 IWL-2320: The Responsible Engineer Conduct of all examinations and evaluation of examination

results is the responsibility of a person called the ResponsibleEngineer. This person must be a Registered Professional Engineerexperienced in evaluating the condition of structural concrete,with knowledge of the Design Codes, Construction Codes, andother criteria used in design and construction of concrete contain-ments in nuclear power plants. The Responsible Engineer must dothe following:

(1) develop plans and procedures for examinations; (2) supervise the instruction, training, and approval of concrete

examination personnel; (3) perform or direct visual examinations; and (4) evaluate the examination results.

28.24 IWB/IWC/IWD/IWE/IWF/IWL-2400:INSPECTION SCHEDULE

The required examinations must be distributed over the dura-tion of the inspection interval, to ensure that each successiveexamination of a given weld or area is performed at regularintervals.

The required examinations are distributed over the duration ofeach inspection interval, so that successive examinations of agiven weld or area are performed at regular intervals of approxi-mately 10 yr. To accomplish this objective, each interval is divid-ed into three 40-mo. periods.

Inservice examinations and system pressure tests may be per-formed during plant outages, such as refueling shutdowns ormaintenance shutdowns.

28.24.1 IWB-2411: Inspection Program The required percentage of examinations in each Examination

Category must performed in accordance with the schedulingrequirements provided in Table IWB-2412-1, which provides aschedule that distributes the required examinations over the three40-mo. periods of each inspection interval. This distribution isbased on the Examination Category rather than the Item Number,as stated in Interpretation XI-1-86-74, which follows.

Question: Is it a requirement of Section XI, Division 1, toapply the schedule requirements of IWB-2412 and IWC-2412to each Examination Category or to each item number listedin Table IWB-2500-1 and Table IWC-2500-1?

Reply: Schedule requirements are applied by category.

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 13

Page 14: Asme Companion

14 • Chapter 28

Several exemptions to the required distribution of these inspec-tions are provided. These exemptions include the examination ofinternal surfaces of the reactor vessel and the internal surfaces ofClass 1 pumps, and valves. In addition, these exemptions includeexamination of all or portions of the pressure-retaining welds andinterior surfaces of the reactor vessel and other Class 1 vessels, aswell as the internal surfaces of Class 1 pumps and valves, and theflanges and flange bolting of Class 1 pumps, valves, and vessels.Pressure testing is yet another exemption. Some of these examina-tions are required to be performed only once at each refuelingoutage—when the reactor vessel is opened for refueling, at whichtime the surfaces and welds become more accessible for examina-tion. Some others, however, are performed only when a Class 1valve is opened for maintenance or other examination. Pressuretesting is always performed at the end of each refueling outage.

If there are fewer than three items or welds to be examined inan Examination Category, the items may be examined during anyone or two periods, if there are only one or two items or welds,respectively. If items or welds are added to the InspectionProgram during the service lifetime of the plant, 25% of theexaminations required by the applicable Examination Categoryand Item Number for the added items or welds must be performedduring each of the remaining periods of that interval, unless defer-ral to the end of the interval is permitted.

28.25 IWL-2400: INSPECTION SCHEDULE

Concrete vessels and post-tensioning systems are examined ona different schedule from other components. Both are examinedone, three, and five years following completion of the structuralintegrity test, and every five years thereafter. The 1-, 3-, and 5-yr.examinations are completed within 6 mo. of the anniversary date.The 10-yr. and subsequent examinations are completed within 1 yr. of the anniversary date. Any examinations that cannot beperformed at the required time are deferred until the next regularly-scheduled plant outage. In addition, following the one-year exam-ination at sites with multiple plants using the same prestressingsystem and essentially identical design, the examinations may bealternated between the multiple units, so that following the 3-yr. examination, each unit is examined only once every 10 yr.

28.26 IWB/IWC/IWD/IWE/IWF-2420:SUCCESSIVE INSPECTIONS

The sequence of component examinations established duringthe first inspection interval shall be repeated during each succes-sive inspection interval, to the extent practical. This means that, inany given period, the components or welds that are examined are,to the extent practical, the same as those that were examined dur-ing the same period of the previous interval.

In lieu of performing corrective action for defects identifiedduring an inservice examination, a component may be acceptedfor continued service in accordance with the analytical evaluationprovisions of IWB-3132.3 or IWB-3142.4 for Class 1 compo-nents; IWC-3122.3 or IWC-3132.3 for Class 2 components; orIWD-3000 for Class 3 components; the evaluation provisions ofIWE-3000 for Class MC components and Class CC liners; or theevaluation or testing provisions of IWF-3112.2 or IWF-3122.2 forcomponent supports. Because all accessible surface areas of con-crete containments and unbonded post-tensioning systems are

examined on a regular schedule (i.e., every 5 or 10 yr.), there areno similar provisions in Subsection IWL.

If analytical evaluation is used for acceptance, in lieu of correc-tive action, the areas containing flaws or relevant conditions mustbe reexamined during the next three inspection periods for Class 1components or the next inspection period for Class 2, 3, or MCcomponents or Class CC liners, or their supports (IWF). If thesesuccessive reexaminations (three for Class 1 components and onefor Class 2, 3, MC, or CC components, or their supports) revealthat the flaws or relevant conditions have remained essentiallyunchanged for three successive inspection periods, the componentexamination schedule may revert to the original schedule of suc-cessive inspections.

In the 2002 Addenda, new requirements were added for evalua-tion of flaws in Class 3 components. Until that time, the Article wasshow in course of preparation. Much of IWD-3000 is still not com-plete. The new requirements are consistent with those for Class 2components, adjusted for the kinds of examinations required.

For steam-generator tubing, the successive examinationrequirements are left up to the plant Technical Specifications.

If welded attachments are examined as a result of identifiedcomponent support deformation, and the results of these examina-tions exceed the acceptance standards of Table IWB-3410-1, theneed for successive examinations is determined by an evaluationby the Owner.

28.27 IWB/IWC/IWD/IWE/IWF-2430:ADDITIONAL EXAMINATIONS

Examinations performed in accordance with Table IWB/IWC/IWD-2500-1, except for Examination Categories B-P, C-H, andD-B (pressure tests), that reveal flaws or relevant conditionsexceeding the acceptance standards of Table IWB/IWC-3410-1 orIWD-3000 must be extended to include additional examinationsduring the current outage. The additional examinations mustinclude additional welds, areas, or parts included in the inspectionitem that are selected from welds, areas, or parts of similar mater-ial and service, or are subject to the same failure mechanism. Thenumber of additional required examinations varies with the CodeClass of the item. For Class 1, the number of additional examina-tions is equal to the number of welds, areas, or parts in the inspec-tion item that were scheduled to be performed during the presentinspection period. For Classes 2 and 3, the number of additionalexaminations is equal to 20% of the number of weld, areas, orparts in the inspection item that were scheduled to be performedduring the current inspection interval. This additional selectionmay require inclusion of piping systems other than the one con-taining the flaws or relevant conditions.

If this expanded sample reveals additional flaws or relevantconditions exceeding the acceptance standards of TableIWB/IWC-3410-1 or IWD-3000, the examinations shall be fur-ther extended to include the remaining number of welds, areas, orparts of similar material and service subject to the same type offlaws or other relevant conditions, or subject to the same failuremechanism.

For component supports (IWF), the sample expansion provi-sions are far more complex. The first expansion is to include thecomponent supports immediately adjacent to those supports forwhich corrective action is required. The number of additional sup-ports to be examined is to be the same as the number of supportsof the same type and function scheduled to be examined during

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 14

Page 15: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 15

the current inspection period. The second expansion includes theremaining component supports within the system of the same typeand function. If failures are found in this second expanded sam-ple, the third expansion includes nonexempt supports potentiallysubject to the same failure modes identified in either of the twoprevious expansions. When the support failures requiring correc-tive measures indicate non–system-related support failure modes,this third expanded sample must also include nonexempt compo-nent supports in other systems. Finally, if this third expandedsample identifies flaws or relevant conditions exceeding theapplicable acceptance standards, exempted supports that could beaffected by the same failure modes must also be examined. Notethat these sample expansion requirements apply only if correctiveaction is required, not if the results of the examination meet theacceptance criteria and corrective action is performed even thoughit is not required.

For the inspection period following the period in which theexpanded sample examinations were completed, the examinationsare to be performed as originally scheduled in accordance withIWB/IWC/IWD/IWF-2400. If any welds, areas, or parts that wereexamined as part of the expanded sample are scheduled to beexamined in the next period, they must be examined again inaccordance with the original schedule.

The reader should note that IWE-2430 was deleted in the 1998Edition. Beginning with the 1998 Edition, there are no require-ments for additional examinations of Class MC vessels or ClassCC liners as a result of the defects found during inservice exami-nations. In addition, because concrete vessels and post-tensioningsystems are examined in their entirety on a periodic basis (every 5or 10 yr.), sample expansion is not applicable.

For steam-generator tubing, additional examinations are gov-erned by plant Technical Specifications. Section XI does not pro-vide any guidance for examination of steam-generator tubing.

Section XI does not require examination of components as aresult of having identified component support deformation.However, it does require that if welded attachments are examinedas a result of identified component support deformation, and theresults of these examinations exceed the acceptance standards ofTable IWB/IWC-3410-1 or IWD-3000, successive examinationsare to be based on an evaluation by the Owner.

28.28 IWB/IWC/IWD/IWE/IWF-2500:EXAMINATION AND PRESSURE TEST REQUIREMENTS

Components and parts of the pressure-retaining boundary are tobe examined and tested in accordance with the examination methodstabulated in Table IWB/IWC/IWD/IWE/IWF-2500-1 except whenalternative methods are used as permitted by IWA-2240. Thesetables provide examination requirements based on different cate-gories of components, parts, and areas to be examined. For example,the Class 1 Component Examination Categories are as follows:

Table IWB-2500-1, presented in this chapter as Table 28.1, is atypical Examination Category Table. All of the tables for the vari-ous Examination Categories, such as the one shown in Table 28.1,have several common elements. There is a table for each of theExamination Categories listed in IWB/IWC/IWD/IWE/IWF-2500.Each Examination Category, such as the one shown in Table 28.1,is applicable to different components, parts, welds, or examinationlocations, and each table divides the items to be examined intoExamination Item Numbers. These Item Numbers are similar to

Code paragraphs in their structure; for example, in Table 28.1,Items B9.31 and B9.32 are both subsets of Item B9.30.

Each Item Number in an Examination Category table has adescription of the parts to be examined: for example, Item B9.11of Table 28.1 applies to circumferential welds in NPS 4 or largerpiping. Each Item Number is associated with a figure, such as Fig.IWB-2500-8, that displays the area or volume required to beexamined. For each Item Number, an examination method ormethods are specified such as surface and volumetric examinationfor NPS 4 or larger circumferential piping welds in Category B-J.

An acceptance standard paragraph in IWB/IWC/IWD/IWE/ IWF-3000 is specified for each Item Number in an ExaminationCategory table. This referenced paragraph contains acceptance stan-dards for each different type of flaw that may be encountered whenthe specified component, part, or weld is examined. (See Chapter29, “IWB/IWC/IWD/IWE/IWF-3000: Evaluation Standards” foradditional information.)

The next two columns identify how much of the component,part, or weld is required to be examined, and at what frequency.In most cases, the requirements for the first inspection interval arealso applied to all successive inspection intervals.

The last column identifies whether the specified examinationmay be deferred to the end of each interval. Most of the examina-tions that are permitted to be deferred are those applicable to thereactor vessel or its internals, which are not generally accessiblefor examination until the end of the interval, when the fuel isremoved from the reactor vessel, making all of its internal sur-faces and structures accessible. In addition, the examination of theinternal surfaces of Class 1 pumps and valves is permitted to bedeferred until the pump or valve is opened for maintenance.

The footnotes in the Examination Category Tables are veryimportant, for they identify mandatory criteria for selection of theitems to be examined and, in many cases, limit the amount of exam-inations that must be performed. For example, for Categories B-L-2and B-M-2, the VT-3 visual examination of the internal surfaces of

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 15

Page 16: Asme Companion

16 • Chapter 28

pump casings and valve bodies is required only when a pump orvalve is disassembled for maintenance, repair, or volumetric exami-nation, as stated in Interpretation XI-198-22, which follows.

Question (1): For those Class 1 pumps not being disassem-bled during the interval for maintenance, repair, or volumet-ric examination, is it a requirement of Table IWB-2500-1 toperform B-G-1 bolting examinations on at least one pump ineach group of pumps?

Reply (1): No.

Question (2): For those Class 1 valves not being disassembledduring the interval for maintenance, repair, or volumetricexamination, is it a requirement of Table IWB-2500-1 to per-form B-G-2 bolting examinations on at least one valve ineach group of valves?

Reply (2): No.

The following two basic principles were involved in the selec-tion of areas for vessel, pump, valve, and piping examinations:

(1) the highest service factor related to operating conditions,and

(2) representative sampling, selected to provide an assessmentof the general overall condition.

Item (1) of the preceding list, covering the high-service factorareas, includes areas with significantly higher stresses from operat-ing conditions, such as the knuckle joint between the reactor vesselhead and flange, the inside radius section of primary nozzles, or ves-sel material exposed to significant neutron fluence that might affectthe physical properties of the materials. The inspection of thesehigh-service-factor areas generally involves periodic examinations.

For item (2), representative sampling, an attempt is made toprovide sufficient examinations to assess the general overall con-dition. Examples include the representative longitudinal and cir-cumferential weld seams in the reactor vessel; internal vessel sup-ports; weld seams in piping, pumps, and valves; and bolting in thepressure-containing boundary.

The requirements for examination of reactor coolant systemwelds have been significantly increased in recent years, due to theongoing intergranular, transgranular, or primary water stress corro-sion cracking (IGSCC, TGSCC, or PWSCC) in nickel-alloy weldsin reactor coolant environments. This phenomenon was a signifi-cant cause of the corrosion of the reactor pressure vessel head atthe Davis-Besse plant. The industry response has been a signifi-cant increase in the examinations of reactor vessel and reactorcoolant system piping welds for indications of leakage, andchanges in the requirements for evaluation of flaws in those welds.

One of these changes in the acceptance criteria includes a prohibi-tion on use of the Section XI acceptance standards for planar flaws

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 16

Page 17: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 17

in UNS N06600, N06082 or W86182, in BWR or PWR environ-ments, or in stainless steel in BWR environments, in which IGSCC,PWSCC, or TGSCC has occurred. The industry practice for BWRshas been to not use the acceptance standards for stress corrosioncracking, while the acceptance standards for stress corrosion crack-ing have been used for PWRs. These recent changes prohibit suchuse in both environments. The reason for this prohibition is thatcrack growth rates for stress corrosion cracking can be of such highmagnitudes as to cause the acceptance standards to be significantlynonconservative, resulting in a significant safety concern.

Another significant change expected by the time of publicationof this book is a new USNRC requirement to perform the alterna-tive examinations specified by two Section XI Code Cases–N-722, “Additional Inspections for PWR Pressure RetainingWelds in Class 1 Pressure Boundary Components Fabricated withAlloy 600/82/182 Materials, Section XI, Division 1,” and N-729,“Alternative Examination Requirements for PWR Reactor VesselUpper Heads with Partial-Penetration Welds, Section XI,Division 1.” These two Cases provide for additional examinations–primarily visual–for detection of leakage that would indicatesome form of stress corrosion cracking.

28.29 UNIQUE ASPECTS OF CONTAINMENTVESSEL EXAMINATION

28.29.1 IWE-2500: Examination and Pressure TestRequirements

Augmented examination of surface areas subject to accelerateddegradation, as defined in IWE-1242, must be examined as fol-lows: Areas accessible from both sides are examined by detailedvisual examination. Areas accessible from one side only areexamined by ultrasonic thickness measurement to determine theminimum wall thickness in grids not exceeding 1 ft. square. As ofthe 2001 Edition, examination of a component, part, or appurte-nance is permitted from only one side, when only that side is sub-ject to conditions that warrant augmented visual examination inaccordance with IWE-1241, even if both sides of the component,part, or appurtenance are accessible. The revision also limited therequirement for ultrasonic thickness measurement to only when avisual examination cannot be performed on the side subject toconditions that warrant augmented examination. The revision alsopermits use of a statistical sampling plan to be used to select thenumber of grids to be examined within an examination area, inlieu of requiring examinations at grid line intersections.

28.29.2 IWE-2600: Condition of the Surface to Be Examined

Visual examinations of painted or coated surfaces are performedwithout removal of the paint or coating. When removal of paint orcoating is required, the surfaces are examined before removal.

28.30 IWL-2500: EXAMINATIONREQUIREMENTS

28.30.1 IWL-2510: Surface Examination Concrete surface areas and tendon anchorage areas (including

coated areas) are visually examined for evidence of conditionsindicative of damage or degradation, such as those defined in ACI201.1. Selected areas, such as those that indicate suspect conditions,are subject to detailed visual examination. Concrete surface areas

and tendon anchorage areas in containments with unbonded post-tensioning systems are examined for corrosion protection mediumleakage, and tendon end caps are examined for deformation.

Both of the aforementioned examinations are performed by orunder the direction of the Responsible Engineer. Unless temporaryclose-in access is required by the inspection plan, these examina-tions may be performed on floors, roofs, platforms, walkways, lad-ders, ground surfaces, or other permanent vantage points.

28.30.2 IWL-2520: Examination of Unbonded Post-tensioning Systems

Unbonded post-tensioning systems are examined by samplingtendons by force and elongation measurements. Tendon wires areremoved for examination for corrosion and mechanical damage andare tested for yield strength, ultimate tensile strength, and percentelongation. Tendon end anchorage areas are examined for concretecracks; corrosion; broken or protruding wires; missing buttonheads;broken strands; and cracks. These areas are also examined for thequantity of free water. Samples of the corrosion-protection mediumare taken for laboratory analysis to determine reserve alkalinity,water content, and concentrations of water-soluble chlorides,nitrates, and sulfides. Free-water samples are analyzed to determinetheir pH levels. The 2007 Addenda clarified that the corrosion pro-tection medium has to be replaced following completion of post-tensioning system tests and examination, to ensure sufficient cover-age of anchorage hardware, wires, and strands. (See Chapter 32 foradditional information regarding these examinations.)

28.31 UNIQUE ASPECTS OF THECOMPONENT SUPPORTEXAMINATION

28.31.1 IWF-2500: Examination Requirements Examination of component supports includes the following:

(1) Mechanical connections to pressure-retaining componentsand building structure.

(2) Weld connections to building structure. (3) Welded mechanical connections and intermediate joints in

multiconnected integral and nonintegral supports. (4) Clearance of guides and stops, alignment of supports, and

assembly of support items. (5) Hot or cold settings of spring supports and constant-load

supports. (6) Accessible sliding surfaces.

28.31.2 Examination of SnubbersPrior to the 2006 Addenda, both Subsection IWF and the O&M

Code had requirements to visually examine and test snubbers. Thiswas a duplication of requirements and had two standards commit-tees responsible for the same scope. The 2006 Addenda deleted thesnubber examination requirements from Section XI and left snub-ber examinations to the O&M Code. Only snubber repair/replace-ment activities are still within the scope of Section XI.

28.32 IWA-5000: SYSTEM PRESSURE TESTS

This Article addresses performance of two kinds of pressuretests. One is a periodic system pressure test, which is performed ona regular basis to verify leak-tightness of piping and componentsin operating nuclear power plants. The other test is performed

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 17

Page 18: Asme Companion

18 • Chapter 28

following the completion of a repair/replacement activity and isused to verify leak-tightness of new or repaired piping and compo-nents before returning the piping system to service. The periodicsystem pressure test is addressed in the following paragraphs; therepair/replacement pressure test is addressed in Chapter 27.

The 1990s saw significant changes in the pressure testingrequirements precipitated in part by approval of Case N-416,Alternative Rules for Hydrostatic Testing of Repair or Replacementof Class 2 Piping, Section XI, Division 1, published in 1985. ThisCase permitted deferral of Class 2 hydrostatic tests followingrepair/replacement activities to the 10-yr. hydrostatic test that wasrequired to be performed at the end of each inspection interval. Thisdeferral was justified by performance of a system leakage test fol-lowing the repair/replacement activity and before plant startup.

Case N-498, Alternative Rules for 10-Year HydrostaticPressure Testing for Class 1 and 2 Systems, Section XI, Division1, which was approved around 1991, extended the idea of thenear-equivalence of system leakage tests to hydrostatic tests. ThisCase permitted substitution of system leakage tests for the 10-yr.hydrostatic tests. The original version of this Case, N-498,allowed substitution of system leakage tests for hydrostatic testsfor only Class 1 and 2 systems. The first revision of the Case, N-498-1, Alternative Rules for 10-Year Hydrostatic Pressure Testingfor Class 1, 2, and 3 Systems, Section XI, Division 1, approvedaround 1994; also permitted substitution of system leakage testsfor hydrostatic tests in Class 3 systems. Subsequently, Case N-416 was revised (N-416-1) to permit elimination of hydrostatictesting for repair/replacement activities and has been revised toinclude Class 1 and 3 systems, as well as Class 2 systems.

The provisions of the original Case N-498 were added to IWA-5000 and to Tables IWB-2500-1, Examination Category B-P, andIWC-2500-1, Examination Category C-H, in the 1993 Addenda.The provisions of Case N-498-1 through N-498-4, which alloweda similar substitution of system leakage tests for system hydrosta-tic tests in Class 3 systems, were added to Table IWD-2500-1 inthe 2001 Edition. The provisions of Case N-416-1 were incorpo-rated into IWA-4540 in the 1999 Addenda.

The reader should note that most utilities (and probably all U.S.utilities) are using Cases N-416-1 and N-498-1 to eliminate allhydrostatic testing.

The basis behind the provisions of Cases N-416 and N-498 andthe revisions to IWA-4000 and IWA-5000 is that the difference inpressure between a system leakage test and a system hydrostatictest does not provide added benefits commensurate with the diffi-culty of applying the higher test pressure in an operating nuclearpower plant. The Committee felt that the structural integrity of thejoints to be tested would be adequately demonstrated by perfor-mance of appropriate nondestructive examination. For Case N-416-1, the examinations are specified on the basis of thoseexaminations conducted as part of a repair/replacement activity;for Case N-498, the applicable examinations are those specified inthe Owner’s ISI Program.

For the examination requirements of Case N-416-1, theCommittee selected specific provisions of Section III, Division 1.The selected provisions include both the test method and theapplicable acceptance criteria. The test method includes only theterm method as defined in Section V. The nondestructive exami-nation method is typically radiographic or magnetic particle orliquid penetrant examination, and sometimes ultrasonic examina-tion. The examination method does not include the test methodol-ogy, which includes such characteristics as penetrameter selectionand geometric unsharpness. These characteristics may be selected

from the original Construction Code, later Editions or Addenda ofthat Code, or Section III.

In addition, the Committee elected to specify the 1989 Editionof Section III in Case N-416-1. This Edition was selected becauseit was the latest one published at the time of approval of Case N-416-1, and because it included the changes in the 1989 Addendato Section III that permitted ultrasonic examination in lieu of radi-ography for corner joints.

The USNRC asked the Committee to include mandatory volu-metric examination for all Class 3 welds, but the Committee feltthat this extra nondestructive examination was unwarranted.Consequently, in its approval of use of Case N-416-1 in responseto requests from various U.S. utilities, the USNRC added a stipu-lation that all Class 3 welds must be examined by the liquid pene-trant method on both the root pass and the final weld surface.However, the USNRC may not have addressed the fact that Class2 welds up to NPS 4 do not get a volumetric examination. Indeed,the USNRC did not impose such an examination on these Class 2welds, thus making the requirements for these welds less restric-tive than those for Class 3 welds.

After incorporating these provisions into IWA-4540, theCommittee decided to delete the requirement to meet the Sectionexamination requirements, and revised IWA-4540 to requiremeeting only the provisions of the Construction Code andOwner’s Requirements.

It is hoped that the foregoing discussion has provided the read-er with sufficient background for the discussion that follows. Thisdiscussion concerns the performance of pressure testing in operat-ing nuclear power plants and is based on the assumption that anyutility implementing Section XI is or will be using the provisionsof Cases N-416 and N-498 or the revised provisions of IWA-4540and IWA/IWB/IWC/IWD-5000.

28.33 IWA-5110: PERIODIC SYSTEMPRESSURE TESTS

When a piping system that is outside the scope of Section XIpenetrates the containment vessel, the portion of piping penetratingthe vessel and between the inboard and outboard containment isola-tion valves is normally considered Class 2. For this reason, it wouldordinarily be subject to the pressure testing requirements ofSubsection IWC. However, the Subsection IWC pressure testingrequirements are inappropriate for this section of piping. Therefore,this piping is exempt from periodic system pressure tests.

28.34 IWA-5120: SYSTEM PRESSURE TESTSFOR REPAIR/REPLACEMENTACTIVITIES

This Subsubarticle provides requirements for performance ofpressure testing following repair/replacement activities. Thischapter does not address this subject because Chapter 27 addressesit in detail.

28.35 IWA-5200: SYSTEM TESTREQUIREMENTS

Section XI specifies three pressure test methods: system leakagetests, system hydrostatic tests, and system pneumatic tests. Theterm system leakage test includes three tests that were formerly

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 18

Page 19: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 19

known as system leakage tests, system inservice tests, and systemfunctional tests. The 1991 Addenda incorporated all three termsinto the term system leakage tests.

The system leakage test may be conducted during operation atnominal operating pressure or when the system is pressurized tonominal operating pressure and temperature during functional orpreoperational testing. The system hydrostatic test is performedwhen the plant is not in operation and is performed at a pressureabove nominal operating pressure and up to about 25% higherthan nominal operating pressure. The system pneumatic test isconducted with air as the pressurizing medium; it is permitted forClass 2 or 3 components as an alternative to either the systemleakage test or the system hydrostatic test.

Before the 1991 Addenda, the system leakage test was intendedto be applied only to Class 1 systems. The system functional testapplied to a test conducted to verify operability in systems notrequired to operate during normal plant operation; these testswere not dictated by Section XI but by regulatory requirementsfor verifying operability. The system inservice test applied toClass 2 and 3 systems that were to be examined while the systemwas in service under operating pressure.

Both system leakage tests and system hydrostatic tests are con-ducted at pressures and temperatures specified in IWB/IWC/IWD-5000. If a system hydrostatic test is conducted, it may not exceedthe maximum allowable test pressure of any component within thesystem pressure test boundary. When a system leakage test is con-ducted, the level of system pressure and temperature indicated orrecorded by normal operating system instrumentation or by testinstrumentation is acceptable—in other words, exact system pres-sure or temperature requirements for this test are not specified; thetest is to be conducted when the plant operator determines that thesystem is in normal operation. In addition, specially calibratedpressure test gauges are not required for measuring the test pres-sure. The test conditions are maintained essentially constant duringthe visual examination except as required to avoid conducting thetest at a temperature above 200�F, to ensure personnel safety.

When portions of the system are subject to pressure testsassociated with two different system functions, such as a normaloperating function and an emergency system function, the visualexamination must be performed only during the test conducted atthe higher of the test pressures of the respective system functions.

28.35.1 IWA-5213: Test Condition Holding Time The holding time after pressurization to test conditions, before

beginning the visual examinations, is as follows:

(a) For periodic pressure tests, (1) For Class 1 components, no holding time is required

after attaining test pressure. (2) For Class 2 components not required to operate during

normal plant operation, a 10 min. holding time isrequired after attaining test pressure.

(3) For Class 2 components required to operate during nor-mal plant operation, no holding time is required, pro-vided the system has been in operation for at least 4 hr.for insulated components or 10 min. for noninsulatedcomponents.

(b) For system pressure tests required by IWA-4540, a 10 min.holding time for noninsulated components, or 4 hr. for insu-lated components, is required after attaining test pressure.

(c) For system pneumatic tests, a 10 min. holding time isrequired after attaining test pressure.

These provisions were revised in the 2003 Addenda to increasethe holding time for periodic pressure tests. This revisionaddressed an NRC concern that the previous holding time require-ments were not long enough to ensure detection of through-wallpressure-boundary leakage.

28.35.2 IWA-5214: Preservice Test A preservice system pressure test is not required except after

repair/replacement activities as required by IWA-5120.

28.36 IWA/IWB/IWC/IWD-5220: TESTPRESSURIZATION BOUNDARIES

The boundary subject to test pressurization during the systemleakage test includes all pressure-retaining components underoperating pressures during normal system service. The boundarysubject to test pressurization during the system hydrostatic test, orthe end-of-interval system leakage test, includes all componentshaving the same minimum required classification and designed tothe same pressure rating as governed by the system function andthe internal fluid operating conditions. Systems having differentsafety functions for different modes of operation are subject toseparate system hydrostatic or system leakage tests of each por-tion of the system boundary having the same minimum requireddesign pressure rating. Systems operating at different pressuresunder different modes of plant operation or post-accident condi-tions are subject to hydrostatic or system leakage tests within theboundary defined by the operating mode with the higher pressure.For the suction and discharge sides of pumps, the hydrostatic orsystem leakage test boundary is divided into two separate bound-aries: for positive displacement pumps, the boundary is at thepump, and for centrifugal pumps, the boundary is at the first shut-off valve on the discharge side of the pump.

For Class 1 systems, the pressure-retaining boundary during thesystem leakage test must correspond to the reactor coolant systemboundary, with all valves in the position required for normal reac-tor operation startup. The visual examination must include thesecond closed valve at the boundary extremity. The pressure-retaining boundary during the system leakage tests conducted ator near the end of each inspection interval must include all Class1 pressure-retaining components within the system boundary.

For Class 2 and 3 systems, the pressure-retaining boundaryduring the system leakage test must include only those portions ofthe system required to operate or support the safety functions upto and including the first normally closed valve—including a safe-ty relief valve or a valve capable of automatic closure—when thesafety function is required. Items outside these boundaries, aswell as open-ended discharge piping, are excluded from theexamination requirements.

28.37 IWA-5240: VISUAL EXAMINATION

The VT-2 visual examinations are conducted by examining theaccessible external exposed surfaces of pressure-retaining compo-nents for evidence of leakage. When the external surfaces areinaccessible for direct VT-2 visual examination, the surroundingarea is examined for evidence of leakage. When systems areborated for the purpose of controlling reactivity, such as the reactor-coolant system or the standby liquid-control system, insulationmust be removed from pressure-retaining bolted connections for

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 19

Page 20: Asme Companion

20 • Chapter 28

the VT-2 visual examination. For other components, the examina-tion may be conducted by examining the accessible and exposedsurfaces and joints of the insulation. The examination of insulatedcomponents must also include floor areas, equipment surfaces,and other areas into which such leakage may be channeled.Particular attention is paid to detection of discoloration or residueon surfaces that may indicate evidence of boric acid accumulationfrom borated reactor coolant system leakage.

The 2001 Edition permitted deferral of insulation removal andVT-2 visual examination of pressure-retaining bolted connectionsin insulated, hot, borated systems until the system is depressur-ized and cooled. A VT-2 visual examination must be performedwith the insulation removed, but the system need not be pressur-ized for this examination. No hold time is required prior to theVT-2 visual examination. The 2003 Addenda permitted the VT-2examinations of bolted connections on systems borated for thepurpose of controlling reactivity to be performed without insula-tion removal, if the bolting material is resistant to boric acid cor-rosion (i.e., stainless steel or high-alloy steel).

28.37.1 IWA-5244: Buried Components For buried components, when the VT-2 visual examination can-

not be performed, the examination may consist of a test to verifythat flow during operation is not impaired, or, for isolatable por-tions of the system, by a pressure drop test or a change-in-flowtest. The test personnel for these tests do not need to be qualifiedVT-2 examination personnel.

28.38 IWA-5250: CORRECTIVE ACTION

The sources of any leakage detected during the conduct of thesystem pressure test must be located and evaluated by the Ownerto determine whether corrective action is required. Buried compo-nents with leakage losses in excess of limits acceptable for con-tinued service must be corrected.

IWA-5250 is frequently misunderstood. Most members of theapplicable ASME Committees agree that this paragraph permitsevaluation of through-wall pressure boundary leakage, but somemembers believe that through-wall pressure boundary leakageshould not be permitted by the ASME Code. Such individualsuse the phrase “evaluated by the Owner for corrective action” tosupport their position that corrective action must be performedwhen leakage is detected. Although this is not a logical interpre-tation of these words, it does carry a significant amount ofimportance because many individuals at the USNRC support andendorse it.

In support of the ASME Code Committee’s prevailing opinion,IWB-3522.1 requires that relevant conditions detected duringsystem pressure tests require correction to meet the requirementsof IWB-3142 and IWA-5250 before continued service. Relevantconditions are defined in IWA-9000 as conditions observed duringthe visual examination requiring supplemental examination, cor-rective measures, correction by repair/replacement activities, oranalytical evaluation. The referenced IWB-3142 permits accep-tance by visual examination, supplemental examination, correc-tive measures, repair/replacement activity, or analytical evalua-tion, provisions clearly allowing the evaluation of through-wallpressure boundary leakage without necessarily requiring correc-tion by repair/replacement activities.

In addition, the interpretation that corrective action must beperformed when leakage is detected should logically be applied to

leakage through gasketed joints or other locations where leakage isexpected. However, this interpretation is usually selectively appliedto support the position that only through-wall pressure boundaryleakage must be corrected by repair/replacement activities.

The logic of the ASME Code Committee’s prevailing opinionbecomes largely academic, however, because IWB-3144requires that whenever the evaluation analyses are used insteadof repair/replacement activities to justify acceptance, the analy-ses must be submitted to the regulatory authority having juris-diction at the plant site. This provision, at least in the UnitedStates, gives considerable importance to the USNRC’s interpre-tation that through-wall pressure boundary leakage must be cor-rected by repair/replacement activities except when relief isgranted by the USNRC. The ultimate treatment of through-wallpressure boundary leakage, therefore, may be far more politicalthan technical.

It is important to note that this paragraph addresses only leak-age identified during the conduct of a system pressure test, notleakage found during normal operation, operator walkdowns, orother events. Such leakage is not within the jurisdiction of SectionXI. The following two interpretations convey these facts.Interpretation XI-1-92-19:

Question (1): Does leakage identified during the conduct of avisual (VT-2) examination performed in conjunction with aSection XI required pressure test (Table IWA-5210-1), exceed-ing the acceptance criteria of IWB-3000, IWC-3000, andIWD-3000, require corrective measures in accordance withIWA-5250(a) prior to continued service?

Reply (1): Yes.

Question (2): Does leakage identified during the conduct ofnormal plant operation not in conjunction with a Section XIrequired pressure test (Table IWA-5210-1) require correctivemeasures in accordance with IWA-5250(a)?

Reply (2): No. Section XI, IWA-5250(a) does not apply dur-ing normal plant operation.

Interpretation XI-1-92-03:

Question: Do the provisions of Section XI, IWA-5250 apply toleakage found at times other than during a system pressuretest?

Reply: No.

Section XI does not provide specific methods of correctiveaction. However, Interpretations XI-1-95-26 and XI-1-92-31,which follow, provide some insight into the types of correctiveaction that may be performed.

Interpretation XI-1-95-26:

Question (1): Does Section XI prohibit use of a sealant to stopleakage in flanged joints, valve stuffing boxes, engineeredstructural clamps, or other pressure retaining encapsulationsconstructed in accordance with an applicable ConstructionCode, when the sealant functions like a gasket or packing andis not required for structural integrity, as determined by theevaluation required by IWA-5250 or IWB-3122.4 (IWA-5250,and IWB-3142.4 or IWC-3132.3 in the Winter 1983 or laterAddenda)?

Reply (1): The use of sealants is neither required norprohibited by Section XI.

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 20

Page 21: Asme Companion

COMPANION GUIDE TO THE ASME BOILER & PRESSURE VESSEL CODE • 21

Question (2): Does Section XI prohibit use of a sealant to stopleakage through pressure retaining material, when thesealant functions like a gasket and is not required for struc-tural integrity, as determined by the evaluation required byIWA-5250 or IWB-3122.4 (IWA-5250, and IWB-3142.4 orIWC-3132.3 in the Winter 1983 or later Addenda)?

Reply (2): The use of sealants is neither required nor prohib-ited by Section XI.

Interpretation XI-1-92-31:

Question: If through wall leakage is found during a systempressure test, are the following conditions an acceptable cor-rective action under Section XI, IWA-5250:

(a) the flaw is removed; (b) a closure device (e.g., branch connection, weldolet) meet-

ing the requirements of IWA-4000/IWA-7000 and theConstruction Code or Section III is installed; and

(c) an evaluation considering the extent of the original flawis performed demonstrating that the structural integrityprovisions of the Construction Code or Section III aremet for the component with the closure device installed.

Reply: Yes.

If leakage occurs in a bolted connection of a system borated forthe purpose of controlling reactivity, the bolt closest to the sourceof leakage must be removed, examined, and evaluated. If the bolt-ing is degraded, all remaining bolting in the connection must beremoved and evaluated; if correction is required, anyrepair/replacement activities must be performed in accordancewith IWA-4000. If boric acid residues are detected, the source ofleakage and any areas of general corrosion must be located. Anydegradation of local areas that reduces the wall-thickness by morethan 10% must be evaluated to determine whether the componentis acceptable for continued service. The following interpretationpertains to these facts:

Interpretation XI-1-98-39:

Question: Is it the intent of IWA-5250(a)(2) that bolting beremoved and a VT-3 visual examination be performed onlywhen the system is borated for the purpose of controllingreactivity?

Reply: Yes.

The USNRC has requested that the ASME add requirements toSection XI to address evaluation and acceptance criteria for leak-age, including operational leakage. There are two primary reasonsthat this subject has not been addressed to date. (1) The ASMECommittee has not been able to reach a consensus position on thedegree to which evaluation and acceptance of through-wall leak-age should be permitted. (2) The ASME Committee has beenreluctant to add requirements for sample expansion if leakage isfound during plant operation.

In response to the USNRC request, the ASME Subcommitteeon Nuclear Inservice Inspection has set up a project team to developthese new requirements. This author speculates that (1) it will takeat least a year or two to develop these requirements and obtain aconsensus to approve them, (2) they will allow little or no leakagein a reactor coolant system, and (3) they will contain provisionsfor evaluating and accepting limited leakage in Class 2 or 3systems.

28.39 IWA-5260: INSTRUMENTS FORSYSTEM HYDROSTATIC TESTS

Pressure-measuring instruments or sensors must meet specificrequirements for accuracy, calibration, and ranges. These testinstruments may be located anywhere within the system boundarybeing tested, but they must be used to ensure that the specifiedtest pressure is not exceeded by more than 6% at the location ofthe highest pressure in the system.

28.40 IWA-5300: TEST RECORDS

The record of the visual examination conducted during thesystem pressure test must include the system test condition andthe system pressure boundary. Any source of leakage or evidenceof structural distresses must be itemized, and both the location ofthe leakage and the corrective action documented.

28.41 IWA-6000: RECORDS AND REPORTS

28.41.1 IWA-6200: Requirements The Owner is required to prepare plans and schedules for pre-

service and inservice examinations and tests to meet the SectionXI requirements, and must prepare records of these examinationsand tests as well as of any repair/replacement activities. TheOwner must prepare preservice and inservice inspection summaryreports for Classes 1 and 2 pressure-retaining components andtheir supports for submittal to the applicable regulatory andenforcement authorities. In addition, the Owner must prepare theOwner’s Report for Inservice Inspections (Form NIS-1) for pre-service and inservice examinations of Classes 1 and 2 pressure-retaining components and their supports. The Owner must alsoprepare the Owner’s Report for Repair/Replacement Activities(Form NIS-2) for all Classes of components and supports.

28.42 IWA-6300: RETENTION

The Owner must maintain records and reports and file them ina manner that allows access by the ANII. The Owner must protectall records and reports from deterioration and damage for the ser-vice lifetime of the component or system. The records and reportsmay be stored at either the plant site or another designated loca-tion, in either their original forms or as reproduced, legiblecopies. Radiographs may be microfilmed if the projection of themicrofilm to its original size provides the same informationretrieval capability as the original radiograph. IWA-6340 providesexamples of the records that are required to be maintained; otherrecords are as designated by the Owner.

28.43 RISK-INFORMED INSERVICEINSPECTION

As briefly mentioned by Mr. Hedden in Section 26.2.9.1, theASME Code Committees have been doing substantial work todevelop an alternative approach to determination of what areas tosubject to inservice inspection and what degradation mechanismsthe inservice inspection will be intended to identify. Since the initialpublication of Section XI in 1970, all of the required inspections

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 21

Page 22: Asme Companion

22 • Chapter 28

have been deterministic. That is, the inspection locations have beenspecified based on the best information available to the Committeein 1970, with regard to what degradation would be anticipated tooccur. The examinations have been specified based on samplingthese locations, on the assumption that the degradation processwould be somewhat random.

Based on 40 years of operating experience, we now know thatthere are other active degradation mechanisms that were notpreviously anticipated or recognized. We also have enough infor-mation to more accurately predict the locations at which thesedegradation mechanisms will be active. Furthermore, theCommittee recognized that changing the process for selection ofareas to be subject to inservice inspection could result in a signifi-cant reduction in radiation exposure for the examination person-nel. This reduction results largely from the fact that degradation isnow known to occur to a far greater degree in Class 2 and 3 sys-tems and to a lesser degree in Class 1 systems than previouslyanticipated. In addition, the consequences of failure of certainClass 2 and 3 systems are now known to be greater than oncethought.

Therefore, if we are to focus our efforts on identifying the pres-ence of known active degradation mechanisms with significant riskconsequences, we will shift our focus to place a greater emphasison certain Class 2 and 3 systems and a lesser emphasis on Class 1systems. This does not mean elimination of Class 1 examinations;however, it does allow reduction of the amount of Class 1 exami-nations from, for example, approximately 25% of reactor coolantsystem piping welds to approximately 10% of reactor coolant sys-tem piping welds, while increasing the number of examinations ofwelds in Class 2 and 3 systems. This shift in emphasis can occuronly if it can be showing that the risk of failure is not reduced by achanging the inspection locations and frequencies.

This is where probabilistic risk assessment provides a signifi-cant benefit. The probabilistic risk assessment is the result of acombination of an evaluation of the probability of a postulatedfailure and evaluation of the consequences of that postulated fail-ure. If the probability of failure is high and the consequence offailure is low, the risk level is less than if both the probability andconsequence were high. The same is true if the probability of fail-ure is low but the consequence of that failure is high.Furthermore, if it can be shown that the probability and conse-quence of a postulated failure are both low, the examinationintended to detect that failure mechanism can be eliminated.

The process of development of inspection criteria for nuclearpower plants was begun with Code Cases N-560, N-577, and N-578. The philosophy used to identify the requirements for riskassessment that are used as a basis for selection of locations forexamination in these Code Cases is now presented in a new PRAstandard published by a ASME as Standard for Probabilistic RiskAssessment for Nuclear Power Plant Applications, RA-S.

These three Code Cases have now been used in many U.S.nuclear power plants. As a result of these applications, manylessons have been learned. The result of these lessons is thatSection XI was revised in 2005 to incorporate the most desirable

aspects of these Cases into Nonmandatory Appendix R, “Risk-Informed Inspection Requirements for Piping.” In addition, severalother Cases have been written or are currently in the process ofbeing prepared, to incorporate additional lessons learned. In thenext several years, we can expect that the science of risk-informedinservice inspection will continue to advance very rapidly.

28.44 HIGH-TEMPERATURE GAS-COOLEDREACTORS

Section XI, Division 2 once covered gas-cooled reactors. ThisDivision was intended specifically for the design used at Fort St.Vrain. Because this reactor is no longer in operation, Section XI,Division 2 was discontinued in 1995.

In the last several decades there has been significant researchinto high-temperature gas-cooled reactors. As a result, there areseveral new high-temperature gas-cooled reactor (HTGR) designscurrently being developed and constructed. These include both apebble bed modular design and a prismatic core design. Becausethe designers of these reactors are interested in using ASMESection XI for inservice inspection of these new reactors, SectionXI, Division 2 is now being rewritten.

The most immediate industry need is for inservice inspectioncriteria for the pebble bed modular reactor design. Therefore, thenew Section XI, Division 2 is being written primarily to addressthat design. However, the new division will be flexible enough tobe easily modified to accommodate other reactor designs.

The inservice inspection requirements will be substantially dif-ferent from those for light-water-cooled reactors. The primary dif-ference is that loss of coolant flow in an HTGR will not result in ameltdown of the reactor core fuel elements. This is because thereactor core is designed with a negative reactivity coefficient,which limits the maximum temperature to below the level atwhich significant core damage will occur. Therefore, if a breachof the main heat transfer loop occurs, there will be no substantialexposure to personnel or to the environment from the radiationcontained within the core. Therefore, much of the inspection thatwill be performed during operation of the reactor will be intendedprimarily for investment protection rather than radiological pro-tection. Depending on the reactor design, there may be some sec-ondary systems that are essential to keeping the reactor cool fol-lowing a postulated break in the heat transport system. Inserviceinspection will be focused on such systems.

As mentioned in Section 28.43, Risk-Informed InserviceInspection, the technology today for inservice inspection ofnuclear power plants has been affected significantly by use ofprobabilistic risk assessment. This philosophy is being integratedinto the initial drafts of Division 2. Therefore, Division 2 willprobably have no deterministic inservice inspection requirements,but rather will probably have all of its inspection requirementsbased on probabilistic risk assessment.

This new Section XI, Division 2 is anticipated to be publishedin2009 or 2010.

ASME_Ch28_p001-022.qxd 10/18/08 11:44 AM Page 22