Regulatory Guide 1.148
| ML13038A427 | |
| Person / Time | |
|---|---|
| Issue date: | 03/31/1981 |
| From: | Office of Nuclear Regulatory Research, NRC/OSD |
| To: | |
| References | |
| RG-1.148, Task SC 704-5 | |
| Download: ML13038A427 (6) | |
March 1981U.S. NUCLEAR REGULATORY COMMISSIONREGULATORY GUIDEOFFICE OF STANDARDS DEVELOPMENTREGULATORY GUIDE 1.148(Task SC 704-5)FUNCTIONAL SPECIFICATION FOR ACTIVE VALVE ASSEMBLIESIN SYSTEMS IMPORTANT TO SAFETY IN NUCLEAR POWER PLANTS
A. INTRODUCTION
Criterion 1, "Quality Standards and Records," ofAppendix A, "General Design Criteria for Nuclear PowerPlants," to 10 CFR Part 50, "Domestic Licensing of Produc-tion and Utilization Facilities," requires, in part, thatcomponents important to safety be designed, fabricated,erected, and tested to quality standards commensuratewith the importance of the safety functions to be performed.Section III, "Design Control," of Appendix B, "QualityAssurance Criteria for Nuclear Power Plants and FuelReprocessing Plants," to 10 CFR Part 50 requires, in part,that measures be established to ensure that regulatoryrequirements and the design basis for applicable struc-tures, systems, and components are correctly translatedinto 3pecifications, drawings, procedures, and instructions.This guide delineates a procedure acceptable to the NRCstaff for implementing the Commission's regulations withrespect to the detailed specification of information pertinentto defining operating requirements for valve assemblieswhose safety-related function is to open, close, or regulatefluid flow in light-water-cooled nuclear power plants. Thisguide will be applied to active valve assemblies' in systemsimportant to safety in light-water-cooled nuclear powerplants. The Advisory Committee on Reactor Safeguards hasbeen consulted concerning this guide and has concurred inthe regulatory position.
B. DISCUSSION
The rules for construction of nuclear components givenin Section III, "Nuclear Power Plant Components," of theASME Boiler and Pressure Vessel Code2 (the Code) donot, as indicated in NCA-2142(b) of the 1977 Edition,As identified in accordance with Section 3.9.3.2 of RegulatoryGuide 1.70, Revision 3, "Standard Format and Content of SafetyAnalysis Reports for Nuclear Power Plants."2Copies may be obtained from the American Society of Mechan-ical Engineers United Engineering Center, 345 East 47th Street,New York, N.N. 10017.ensure operability of components in which mechanicalmotion is required. Since valve assembly3 operability isnecessary to ensure performance of some systems importantto safety in nuclear power plants, the American NationalStandards Institute (ANSI) established a group to providedirection for development of the necessary standards thatwould provide assurance of the operability of valve assem-blies. The first standard published as a result of that effortwas ANSI N278.1-1975, "Self-Operated and Power-OperatedSafety-Related Valves Functional Specification Standard."2This standard requires that a functional specification beprepared that (1) identifies the function of the valveassembly in systems important to safety and (2) delineatesthe set of conditions important to valve assembly operability.ANSI N278.1-1975 establishes a consistent approach tospecifying the minimum information needed to identify therequirements for function and operability of valve assem-blies in systems important to safety. Although the standardhas not been extensively used, it is apparent that it wouldbe useful for any Quality Group A, B, C, or D valve assemblyin systems important to safety. However, there are questionsrelative to whether this detailed functional specificationis necessary for all (or for certain specified) valve assembliesin systems important to safety. It is anticipated that thebreadth of application of this standard might developgradually with user experience, quality group classificationof a particular valve assembly, and valve assembly functionwithin a given plant system. In this context, specificationswould most likely evolve from systems analyses and, assuch, could be compatible with applicable system safetycriteria through appropriate use of limit range, maxima,minima, envelope of important parameters, or generallyaccepted approaches consistent with industry practice.It is evident that a thorough process to identify specificvalve assemblies that should have functional specifications3A valve assembly is composed of the pressure-retaining parts ofthe valve body, internals, actuator, and functional accessories.USNRC REGULATORY GUIDESRegulatory Guides are Issued to describe and make available to thepublic methods acceptable to the NRC staff of implementingspecific parts of the Commission's regulations, to delineate tech-niques used by the staff In evaluating specific problems or postu-lated accidents, or to provide guidance to applicants. RegulatoryGuides are no substitutes for regulations, and compliance withthem is not required. Methods and solutions different from those setout in the guides will be acceptable if they provide a basis for thefindings requisite to the issuance or continuance of a permit orlicense by the Commission.Comments and suggestions for improvements in these guides areencouraged at all times, and guides will be revised, as appropriate,to accommodate comments and to reflect new information orexperience. This guide was revised as a result of substantive com-ments received from the public and additional staff review.Comments should be sent to the Secretary of the Commission,U.S. Nuclear Regulatory Commission, Washington, D.C. 20555,Attention: Docketing and Service Branch.The guides are issued in the following ten broad divisions:1. Power Reactors 6. Products2. Research and Test Reactors 7. Transportation3. Fuels and Materials Facilities 8. Occupational Health4. Environmental and Siting 9. Antitrust and Financial Review5. Materials and Plant Protection 10. GeneralCopies of issued guides may be purchased at the current GovernmentPrinting Office price. A subscription service for future guides in spe-cific divisions is available through the Government Printing Office.Information on the subscription service and current GPO prices maybe obtained by writing the U.S. Nuclear Regulatory Commission,Washington, D.C. 20555, Attention: Publications Sales Manage in accordance with this standard would be extremelydifficult because of differing plant system characteristics.One desirable goal for initial application of the standardwould be to provide a relatively wide spectrum of usecovering several Quality Group classifications in order todevelop adequate experience to determine a breadth ofapplication for the standard. The NRC staff believes that"active" valve assemblies identified in accordance withSection 3.9.3.2 of Regulatory Guide 1.70, Revision 3,"Standard Format and Content of Safety Analysis Reportsfor Nuclear Power Plants," are representative of such aspectrum as well as being very important to plant safety.Therefore, the staff proposes that the initial application ofthis standard should, as a minimum, encompass active valveassemblies in systems important to safety.For use with this regulatory guide, the staff intendsthat active valve assemblies should be identified accordingto the guidance provided in Subsection 11.2, "Pump andValve Operability Assurance Program," of Section 3.9.3of the Standard Review Plan. A proposed revision to theStandard Review Plan will also affect previous definitionsof the term "active." The staff plans to use the followingproposed definition:Active valves -valves that, during or followingpostulated accidents, must perform a mechanicalmotion in order to shut down the plant, main-tain the plant in a safe shutdown condition, ormitigate the consequences of a postulated event.Safety and relief valves provided in accordancewith the requirements of ASME Code Section III-e specifically included.It appears that component standards usually concentrateon accomplishing a single goal such as providing pressureboundary integrity even though it may be necessary toaddress a relatively broad subject matter that could includematerials properties, design rules, testing rules, and certifica-tion requirements in order to meet the desired goal. Anexample of this approach isSection III of the Code. Simi-larly,Section XI, "Rules for Inservice Inspection of NuclearPower Plant Components," of the Code provides, as one ofseveral goals, rules for inservice testing of valve assemblies,while ANSI N278.1-1975 is directed toward operability ofvalve assemblies in systems important to safety. It is there-fore evident that the complete spectrum from construction4through operability to inservice testing of a valve assemblyis covered by separate codes and standards even thoughthere is a necessary relationship among them. Hence, thestaff believes that (I)there is a need for a set of comprehen-sive requirements to provide the detailed documentationthat serves as the basis for construction, assurance ofoperability, inservice testing, and applicability of andrelationship among the separate standards and (2) thereshould be both technical compatibility and consistent4As defined in Section III of the Code, "construction" is anall-inclusive term comprising materials, design, fabrication, examina-tion, testing, inspection, and certification required in the manufactureand installation of items.requirements for similar issues among the documents thatmake up the set of comprehensive requirements.Accordingly, those valve assemblies that are classifiedas ASME Code Class 1, 2, or 3 (Quality Groups A, B, and C,respectively, as identified in Regulatory Guide 1.26, "QualityGroup Classifications and Standards for Water-, Steam-, andRadioactive-Waste-Containing Components of NuclearPower Plants") are relatively amenable to meeting a set ofcomprehensive requirements. One approach to aid inproviding.this set of requirements would be to include thefunctional specification requirements of ANSI N278.1-1975with the Design Specification requirements of NCA-3 250 inSection III of the Code. Also, it appears advisable, at leastfor Class 1, 2, and 3 valve assemblies, that the functionalspecification recognize and reference certain relationshipssuch as those pertaining to the use or applicability ofSection Xl and Code Case N-62-2, "Internal and ExternalValve Items." Although the few active valves in systemsimportant to safety that are classified as Quality Group Din Regulatory Guide 1.26 (those that use the ANSI B31.1.02standard) may not have the desired specific relationshipbetween the functional specification and the document thatserves as the basis for construction (the Design Specificationof ASME Code Class 1, 2, and 3 valves), there is still a needfor a set of comprehensive requirements.
C. REGULATORY POSITION
The requirements delineated in ANSI N278.1-1975(I) are generally acceptable to the NRC staff for functionalspecifications of active valve assemblies whose operabilitymust be ensured and (2) provide an adequate basis forcomplying with those requirements of Criterion 1 ofAppendix A and Section III of Appendix B to 10 CFRPart 50 relating to the correct translation into specifications,as supplemented or modified by the following:1. Applicability and Relationship With Other Standardsa. The scope of ANSI N278.1-1975, as stated in Section 1of the standard, should be supplemented to include activemanually operated valve assemblies in systems important tosafety.5b. The phrase design specification relationship, usedin Section 2 of the standard to indicate an interrelationshipwith other codes and standards, should be broadly inter-preted to include a document that contains sufficient detailto serve as a "complete basis for construction" and may,,as appropriate, be called an equipment specification,procurement specification, or some similar term that includesthe Design Specification required by the ASME Code.However, when valve operability is a requirement, thefunctional specification required by N278.1-1975 should beprovided either as part of, or concurrent with, the controllingdocument that serves as the "complete basis for construc-tion." For ASME Code Class 1, 2, and 3 valves, the "Valve5Manually operated valves are those that are operated physicallyby an operator. Power-operated valves may be manually controlledby an operator or automatically controlled.1.148-2 Design Specification" identified in Section 2 of N278. 1-1975should be that required by NCA-3250, "Provision ofDesign Specifications," of Subsection NCA, "GeneralRequirements," of Section III of the Code.c. The valve functional specification should meet thefollowing requirements in the ASME Code:(1) It should be uniquely identified and referencedin the Design Specification in accordance with NCA-3252(a)(6) of Section lII of the Code.(2) It should reference the applicable Design Specifi-cation to permit identification of both documents.(3) It should meet those portions of the filingrequirements of NCA-3256 that call for a copy to be filedat the location of the installation and made available to theenforcement authorities having jurisdiction over the plantinstallation:d. The functional specification prepared in accordancewith N278.1-1975 for valve assemblies classified as QualityGroup D in Regulatory Guide 1.26 should be cross-referencedwith the document that serves as a "complete basis forconstruction" (see Regulatory Position 1.b of this guide).e. When the Valve Design Specification for ASME CodeClass 1, 2, and 3 valve assemblies requires use of ASMECode Cases such as N-62-2, the functional specificationshould consider this aspect, and usage should be consistentwith Regulatory Guide 1.84, "Design and Fabrication CodeCase Acceptability, ASME Section Hii Division 1," andRegulatory Guide 1.85, "Materials Code Case Accept-ability, ASME Section III Division 1."2. Specific Considerationsa. Section 3.1, "Valve Application Characteristics,"should be supplemented by the following:(1) "Manually operated valves" (see RegulatoryPosition l.a) as a separate item to the listing.(2) The functional specification should identifythe relationship or correspondence between the "applicationcharacteristics" of the subject standard and the ValveCategories A, B, C, and D in IWV-2200 of Subsection IWV,"Inservice Testing of Valves in Nuclear Power Plants," ofSection XI of the Code.b. Section 3.2, "Structural Requirements," should besupplemented by the following:(1) The interdependence and number of cycles, ifapplicable, of time, temperatures, pressures, and dynamicloading resulting from plant transients.(2) The time relationship between applied seismicloadings and other concurrent loadings.(3) The frequency response spectra for the operatingbasis earthquake and the safe shutdown earthquake as wellas other potential forcing functions such as those fromattached piping, pumps, restraints, or other equipment asapplied to valves.(4) The maximum static and dynamic differentialpressure (considering all plant operating conditions) thatexists across the closure device, including potential waterhammer, for which valve assembly operation is to be ensured.c. Section 3.3, "Operational Requirements," should besupplemented by the following:(I) The first paragraph should be supplemented torequire that the desired position of the valve assembly inthe event of loss of actuator power be specified, e.g., failopen, fail closed, fail as is.(2) In item e of Section 3.3.1, "Operating Condi-tions," the phrase "Normal and Abnormal Plant Operation"should be interpreted to include the events covered by plant"Operational Modes (Condition),"'6 and by the Transientand Accident Classification of Chapter 15, "Accident Anal-ysis," of Regulatory Guide 1.70. The functional specificationshould state whether the specific valve assembly safetyfunction applies to events defined in the plant OperationalModes (Condition) or in the Transient and Accident Classi-fication. The specification should also indicate whether theactual valve assembly operation (open, close, or regulatefluid flow) occurs during or after the specified event.(3) instead of item e of 3.3. 2, the following should beused: "e. motor power and duty requirements, includingstall current."(4) Instead of Section 3.3.2.1, "Electrical Power forValve Actuators and Control Elements," the followingshould be used:"Electrical power shall be identified as AC (singlephase or three phase) or DC. Applicable voltageand frequency operating ranges shall be specified."(5) In Section 3.3.3, "Environmental Conditions," theterms "normal" and "abnormal" environmental conditionsshould be interpreted to mean the environmental conditionsthat will exist as a result of specified plant conditions. Theterm "environmental conditions" should be interpreted toinclude both the environment external to the valve assemblyand that of the controlled fluid inside the valve assembly.d. Section 3.4, "Seat Leakage Limits," should besupplemented, as applicable, by the following:6As defined in the Standard Technical Specifications for Westing-house, Combustion Engineering. and Babcock and Wilcox PressurizedWater Reactors. The Standard Technical Specification for GeneralElectric Boiling Water Reactors uses the word "Condition" ratherthan "Modes."1.148-3 (I) The leakage limits identified in paragraph bof this section should include identification of fluid,temperature, and differential pressure for which .the limitapplies.(2) If valve assembly function requires a limit onoverall leakage (e.g., leakage in addition to that of themain seat, such as stem packing and flange), such overallleakage limit should be specified in this section.
D. IMPLEMENTATION
Except- in those cases in which an applicant proposes anacceptable alternative method for complying with specifiedportions of the Commission's regulations, the methoddescribed in this guide will be used in the evaluation of(1) construction permit applications, (2) standard referencesystem preliminary design applications (PDA) or Type-2final design applications (FDA-2), and (3) licenses tomanufacture that are docketed after July 1, 1981, exceptthose portions of a construction permit application that:a. Reference an approved standard reference systempreliminary or final design (PDA or FDA), or an applicationfor approval of such design.b. Reference an approved standard duplicate plantpreliminary or final design (PDDA or FDDA).c. Reference parts of a base plant design qualifiedand approved for replication.d. Reference a plant design approved or under review forapproval for manufacture under a Manufacturing License.This guide will also be used as the basis for evaluatingnew systems important to safety and replacement valveunits ordered after July 1, 1981, for plants that are operat-ing or under construction.1.148-4 VALUE/IMPACT STATEMENTBackgroundValve assemblies (i.e., pressure-retaining portions of thevalve, its internals, its actuator, and attached functionalaccessories) installed in nuclear power plants have experi-enced numerous malfunctions in the past. Licensee EventReports (LERs) show that these malfunctions occur at afrequency that is cause for concern. Approximately 3440LERs were received over the period from 1969 to July 1,1980. The origin of valve assembly malfunctions varieswidely; however, one of the major problems that wasrecognized at the valve operability meeting held withindustry on November 20, i 972, is that equipment specifica-tions are deficient in defining the application and theenvironmental and loading conditions for valve assembliesin nuclear power plants. As a result of the 1972 meeting,effort on developing valve operability standards was initiatedunder the auspices of the American National StandardsInstitute Committee N45. Subsequently, this standardsdevelopment responsibility was transferred to B 16 Subcom-mittee H. The first of these standards to be published wasANSI N278.1-1975, "Self-Operated and Power-OperatedSafety-Related Valves Functional Specification Standard."The regulatory guide endorses that standard with suggestedsupplemental guidance.ValueAlthough ANSI N278.1-1975 provides requirementsimportant for adequate definition of valve assembly applica-tion and operating conditions, the standard, by itself, willnot provide complete assurance of valve assembly operability.It is anticipated that, the most important contributionsfrom ANSI N278.1-1975 will be realized when subsequentstandards, which are currently being developed to addresssuch topics as valve assembly functional qualification andproduction testing, are in place to provide a set of require-ments covering various aspects of valve assembly operability.However, endorsement of ANSI N278.1-1975 as supple-mented by the regulatory position of the guide will providea uniform basis and approach for specifying the functionalrequirements and operability considerations for any partic-ular valve assembly that has a safety-related function.The guide also emphasizes the need for a set of compre-hensive requirements covering construction, operability,and inservice testing of active valve assemblies in systemsimportant to safety.ImpactThe impact of this regulatory guide is expected to berather limited because licensees are committed to a programto demonstrate valve assembly operability in accordancewith Sections 3.9.3.2 and 3.9.6 of Regulatory Guide 1.70,Revision 3, "Standard Format and Content of SafetyAnalysis Reports for Nuclear Power Plants." Additionally,all applicants are cognizant of NRC staff positions on valveassembly operability as identified in Regulatory Guide 1.48,"Design Limits and Loading Combinations for SeismicCategory I Fluid System Components," and Sections 3.9.3and 3.9.6 of the Standard Review Plan. It is thereforeevident that the proposed guide does not introduce a newor additional safety subject.However, ANSI N278.1-1975 was published approxi-mately 5 years ago, and there are indications that it has notbeen extensively used. It appears that the question of whichvalve assemblies should meet the standard determines thepotential impact. Since the staff recommends initial applica-tion of the standard to active valve assemblies, which areaddressed in Section 3.9.3.2 of Regulatory Guide 1.70, theimpact should be restricted to situations where specificdeficiencies exist in individual applicant equipment specifica-tions.A thorough process to identify additional active valveassemblies in systems important to safety that should havefunctional specifications in accordance with ANSI N278.1-1975 would require extensive staff time because differingplant system characteristics make it difficult to establishgeneric groups. The term "safety-related" affects thisprocess because Regulatory Guide 1.26, "Quality GroupClassifications and Standards for Water-, Steam-, andRadioactive-Waste-Containing Components of Nuclear* Power Plants," refers to Quality Groups A, B, C, and D forsafety-related components. However, it may not be desirableor necessary to have all the detail required in the standardfor all valve assemblies that may be classified in accordancewith Regulatory Guide 1.26. Another potential area ofconcern relates primarily to purchasing valve assemblies bya licensee or its agent. Application .of the specificationrequirements of this standard to preselected valve assembliescould adversely affect current purchasing proceduresdepending on whether purchasing is done individually or ingroups of valve assemblies.RecommendationsThe staff intends to apply the guide initially to activevalve assemblies. The guide would, be acceptable for usewith all valve assemblies in systems important to safety, butapplication to other than active valves should be at thediscretion of the licensee because of the potential impacton current procedures. Experience acquired through use ofthe standard with active valve assemblies will provideguidance for wider application in the future.1.148-5 UNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON, 0. C. 2055OFFICIAL BUSINESSPENALTY FOR PRIVATE USE. $300POSTAGE A^NO orES PAiDU.S. NPUCLEAIR REGUL.ATORYCOMMa ISSION