Regulatory Guide 1.105: Difference between revisions

From kanterella
Jump to navigation Jump to search
(Created page by program invented by StriderTol)
(Created page by program invented by StriderTol)
Line 1: Line 1:
{{Adams
{{Adams
| number = ML003740318
| number = ML993560062
| issue date = 02/28/1986
| issue date = 12/31/1999
| title = (Task IC 010-6), Instrument Setpoints for Safety-Related Systems
| title = Setpoints for Safety-Related Instrumentation
| author name =  
| author name =  
| author affiliation = NRC/RES
| author affiliation = NRC/RES
Line 9: Line 9:
| docket =  
| docket =  
| license number =  
| license number =  
| contact person =  
| contact person = Aggarwal S K (301)415-6005
| document report number = RG-1.105, Rev 2
| document report number = RG-1.105, Rev. 3
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 4
| page count = 7
}}
}}
{{#Wiki_filter:Revision 2* 0 ,; U.S. NUCLEAR REGULATORY
{{#Wiki_filter:1ForthefulltextoftheGeneralDesignCriteriaandothersectionsoftheregulationscitedinthisguide,see10CFRPart50,"DomesticLicensingofProductionandUtilizationFacilities."RegulatoryguidesareissuedtodescribeandmakeavailabletothepublicsuchinformationasmethodsacceptabletotheNRCstaffforimplementingspecificpartsoftheNRC'sregulations,techniquesusedbythestaffinevaluatingspecificproblemsorpostulatedaccidents,anddataneededbytheNRCstaffinitsreviewofapplicationsforpermitsandlicenses.Regulatoryguidesarenotsubstitutesforregulations,andcompliancewiththemisnotrequired.MethodsandsolutionsdifferentfromthosesetoutintheguideswillbeacceptableiftheyprovideabasisforthefindingsrequisitetotheissuanceorcontinuanceofapermitorlicensebytheCommission.Thisguidewasissuedafterconsiderationofcommentsreceivedfromthepublic.Commentsandsuggestionsforimprovementsintheseguidesareencour agedatalltimes,andguideswillberevised,asappropriate,toaccommodatecommentsandtoreflectnewinformationorexperience.Writtencommentsmayb esubmittedtotheRulesandDirectivesBranch,ADM,U.S.NuclearRegulatoryCommission,Washington,DC20555-0001.Regulatoryguidesareissuedintenbroaddivisions:1,PowerReactors;2,ResearchandTestReactors;3,FuelsandMaterialsFacilities;4,EnvironmentalandSiting;5,MaterialsandPlantProtection;6,Products;7,Transportation;8,OccupationalHealth;9,AntitrustandFinancialReview;and10,Ge neral.Singlecopiesofregulatoryguides(whichmaybereproduced)maybeobtainedfreeofchargebywritingtheDistributionServicesSection,U.S.Nuclea rRegulatoryCommission,Washington,DC20555-0001,orbyfaxto(301)415-2289,orbyemailtoDISTRIBUTION@NRC.GOV.Manyregulatoryguidesare alsoavailableontheinternetatNRC'shomepageat<WWW.NRC.GOV>.U.S.NUCLEARREGULATORYCOMMISSIONRevision3December1999 REGULATORY
COMMISSION
GUIDEOFFICEOFNUCLEARREGULATORYRESEARCHREGULATORYGUIDE1.105(DraftwasDG-1045)SETPOINTSFORSAFETY-RELATEDINSTRUMENTATION
February 1986 SREGULATO
RY GUIDE OFFICE OF NUCLEAR REGULATORY  
RESEARCH REGULATORY
GUIDE 1.105 (Task IC 010-5)INSTRUMENT
SETPOINTS
FOR SAFETY-RELATED
SYSTEMS


==A. INTRODUCTION==
==A. INTRODUCTION==
Criterion
Criterion13,"InstrumentationandControl," 1ofAppendixA,"GeneralDesignCriteriaforNuclearPowerPlants,"to10CFRPart50,"DomesticLicensingofProductionandUtilizationFacilities,"requires, amongotherthings,thatinstrumentationbeprovidedtomonitorvariablesandsystemsandthatcontrolsbe providedtomaintainthesevariablesandsystemswithinprescribedoperatingranges.Criterion20,"ProtectionSystemFunctions,"ofAppendixAto10CFRPart50requires,amongotherthings,thattheprotectionsystembedesignedtoinitiateoperationofappropriatesystemstoensurethat specifiedacceptablefueldesignlimitsarenotexceeded.Paragraph(c)(1)(ii)(A)of&sect;50.36,"TechnicalSpecifications,"of10CFRPart50requires,inpart,that,wherealimitingsafetysystemsettingisspecifiedforavariableonwhichasafetylimithasbeenplaced, thesettingbesochosenthatautomaticprotectiveactionwillcorrecttheabnormalsituationbeforeasafety limitisexceeded.Italsorequires,amongotherthings,thatthelicenseenotifytheNRCifthelicensee determinesthatanautomaticsafetysystemdoesnotfunctionasrequired.Thelicenseeisrequiredtothen reviewthematterandrecordtheresultsofthereview.
13, "Instrumentation and Control," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," requires, among other things, that instrumentation be provided to moni tor variables and systems and that controls be provided to maintain these variables and systems within prescribed operating range


====s. Criterion ====
2CopiesmaybeobtainedfromtheInstrumentSocietyofAmerica,67AlexanderDrive,ResearchTrianglePark,NC
20, "Protection System Functions," of Appendix A to 10 CFR Part 50 requires, among other things, that the protection system be designed to initiate operation of appropriate systems to ensure that specified acceptable fuel design limits are not exceeded.
20779.2ThisguidedescribesamethodacceptabletotheNRCstaffforcomplyingwiththeNRC'sregulationsforensuringthatsetpointsforsafety-relatedinstrumentationareinitiallywithinandremain withinthetechnicalspecificationlimits.TheguideisbeingrevisedtoendorsePartlofISA-S67.04-1994,
"SetpointsforNuclearSafety-RelatedInstrumentation." 2Thisstandardprovidesabasisforestablishingsetpointsfornuclearinstrumentationforsafetysystemsandaddressesknowncontributingerrorsinthe


Paragraph (cXl)(ii)(A)
channel.Theinformationcollectionscontainedinthisregulatoryguidearecoveredbytherequirementsin10CFRPart50,whichwereapprovedbytheOfficeofManagementandBudget,approvalnumber3150-
of &sect; 50.36, "Technical Specifi cations," of 10 CFR Part 50 requires that, where a limiting safety system setting is specified for a variable on which a safety limit has been placed, the setting be so chosen that automatic protective action will correct the most severe abnormal situation anticipated without exceeding a safety limit. It also requires the licensee to notify the NRC of any automatic safety system mal functions, to review the matter, and to record the results of the review. Setpoints that exceed technical specification limits are considered a malfunction of an automatic safety system.  This guide describes a method acceptable to the NRC staff for complying with the Commission's regulations for ensuring that instrument setpoints are initially within and remain within the technical specification limits.  The Advisory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position.
0011.TheNRCmaynotconductorsponsor,andapersonisnotrequiredtorespondto,acollectionof informationunlessitdisplaysacurrentlyvalidOMBcontrolnumber.
 
iMe substantial number of changes in this revision thas made it Impractical to indicate the changes with lines in the margin.Any information collection activities mentioned in this regulatory guide are contained as requirements in 10 CFR Part 50, which provides the regulatory basis for this guide. The information collection requirements in 10 CFR Part 50 have been cleared under OMB Clear ance No. 3150-0011.


==B. DISCUSSION==
==B. DISCUSSION==
Revision I to Regulatory Guide 1.105, "Instrument Setpoints," was published in November 1976 in response to the large number of reported instances in which instrument setpoints in safety-related systems drifted outside the limits specified in the technical specifications.
Instrumentsetpointuncertaintyallowancesandsetpointdiscrepancieshaveledtoanumberofoperationalproblems.Operatingexperienceindicatesthatsetpointsforsafety-relatedinstrumentationmay allowplantstooperateoutsidethelimitingconditionsofoperationspecifiedintheirtechnical specifications.Licenseeshavediscoveredconflictsbetweenexistingsetpointsandengineering calculations.Thecausesforthesesetpointdiscrepancieswereproblemswithindustrypracticesthatledto errorsincalibrationproceduresandalackofunderstandingoftherelationshipofthesetpointtothe allowablevalue.Additionalproblemsnotedincludedvaryingsetpointmethodologiesforengineering calculations,alackofaconsistentdefinitionofallowablevaluebetweendifferentsetpointmethodologies, andimproperunderstandingoftherelationshipoftheallowablevaluetoearliersetpointterminology, procedures,andoperabilitycriteria.Furtherproblemswerenotedwhenprocedures(thesetpointprocess)
 
(1)failedtoprovideanadequatemarginbetweentheinstrumentas-leftcriteriaandthevalues(tripset pointorallowablevalues)requiredperthetechnicalspecifications,(2)didnotalwaysreflectcurrent designcriteria,and(3)didnotensurethatrevisedinstrumentloopswereverifiedtotheoriginaldesign requirementsorthatinstrumentmodificationswereevaluatedfortheireffectonsetpointcalculations.It hasalsobeennotedthatlicenseesdonottypicallyverifywhethersetpointcalculationdriftassumptions haveremainedvalidforthesystemsurveillanceinterval.ISA-S67.04wasrevisedin1987toprovideclarificationandtoreflectindustrypractice.Theterm"tripsetpoint"wasmadeconsistentwiththeterminologyusedbytheNRCstaff.Thestandardwasrevisedfurtherin1994.Theeffectsofuncertaintyallowancesanddiscrepanciesinsetpoints,alongwithoperationalexperience,wereappropriatelyaddressedduringthisrevisionofISA-
Using the method described in Revision 1 to Regulatory Guide 1.105 and additional criteria on establishing and maintaining setpoints, Subcommittee SP67.04, Setpoints for Safety-Related Instruments in Nuclear Power Plants, under the Nuclear Power Plant Standards Committee of the Instrument Society of America (ISA) has developed a standard containing minimum requirements to be used for establishing and maintaining setpoints of individual instrument channels in safety-related systems. This stan dard is ISA-S67.04-1982, "Setpoints for Nuclear Safety Related Instrumentation Used in Nuclear Power Plants."e*
S67.04.ThisrevisionofthestandardalsoreflectstheImprovedTechnicalSpecificationprogram(a cooperativeeffortbetweenindustryandtheNRCstaff)andreflectcurrentindustrypractice.Thisstandard providesabasisforestablishingsetpointsfornuclearinstrumentationforsafetysystemsandaddresses knowncontributingerrorsinaparticularchannelfromtheprocess(includingtheprimaryelementand sensor)throughandincludingthefinalsetpointdevice.Theterm"tripsetpoint"isretainedinISA-S67.04-1994.However,Figure1inISA-S67.04-1994(forconvenience,thisfigurehasbeenreproducedasFigure1inthisguide)hasbeenrevisedtodepict region"E,""aregionofcalibrationtolerance."Thecalibrationtoleranceuncertaintiesdepictedbyregion
Some key terms used throughout ISA-S67.04-1982 are not defined or have unclear applications.
3Singlecopiesofregulatoryguides,bothactiveanddraft,maybeobtainedfreeofchargebywritingtheOfficeofAdministration,Attn:ReproductionandDistributionServicesSection,U.S.NuclearRegulatoryCommission,Washington,DC20555,orbyfaxto(301)415-2289,orbyemailto<DISTRIBUTION@NRC.GOV>.CopiesarealsoavailableforinspectionorcopyingforafeefromtheNRCPublicDocumentRoomat2120LStreetNW.,
 
Washington,DC;thePDR'smailingaddressisMailStopLL-6,Washington,DC20555;telephone(202)634-3273;
For cun venience, the following information is provided:
fax(202)634-3343.
(1) the definition of the term "safety limit" is contained in 1 50.36 of 10 CFR Part 50, (2) the term "allowable value" as used in the standard is consistent with the usage in the bases sections of the Standard Technical Specification (STS),***
(3) the term "upper setpoint "Copies are available from the Instrument Society of America, P.O. Box 12277, Research Triangle Park, North Carolina 27709. ***NUREG-0103, Revision 4, "Standard Technical Specifica tions for Babcock and Wilcox Pressurized Water Reactors";
NUREG 0123. Revision 3, "Standard Technical Specifications for General Electric Boiling Water Reactors (BWR/S)";
NUREG-0212, Revision 2, "Standard Technical Specifications for Combustion Engineering Pressurized Water Reactors";
and NUREG-0452.-
Revision 4. "Stan dard Technical Specifications for Westinghouse Pressurized Water Reactors." Copies of NUREG-series documents may be purchased from the Superintendent of Documents, U.S. Goverrunent Print.  ing Office, Poet Office Box 37082, Washihston, DC 20013-7082.
 
USNRC REGULATORY
GUIDES Written comments may be suomitted to the Rules and Procedures Branch, DRR ADM, U.S. Nuclear Regulatory Commission, Regulatory Guides are Issued to describe and make avallable to the Washington, oC 20555.  public methods acceptable to the NRC staff of Implementing specific parts of the Commission's regulations, to delineate tech niques used by the staff In evaluating specific problems or postu- The guideo are issuea in tne following tun broad divisions:
lated accidents or to provide guidance to applicants.
 
Regulatory Guides are not substitutes for regulations, and compliance with 1. Power Reactors 6. Products them Is not required.
 
Methods and solutions different from those set 2. Research and Test Reactors 7. Transportation Out in the guides will be acceptable if they provide a basis for the 3. Fuels and Materials Facilities
5. Occupational Health findings requisite to the Issuance or continuance of a permit or 4. Environmental and Siting 9. Antitrust and Financial Review license by the Commission.


5. Materials and Plant Protection
3"E"shouldbedefinedandaccountedforinthelicensee'ssetpointmethodology.Atripsetpointvalueidentifiedtobeoutsideregion"E"regardlessofdirectionrequiresreadjustmenttosatisfythesetpoint methodologyanduncertaintiesidentifiedinFigure1(acceptableas-leftcondition).Itshouldbenotedthat thisstandarddoesnotdefine"nominal"tripsetpoint.ThetripsetpointasdepictedinFigure1isconsistent withtheterm"nominal"tripsetpointasshownaboutadefinedcalibrationtoleranceband.Figure1ofthestandardprovidessetpointrelationshipsfornuclearsafety-relatedsetpoints.Thefiguredenotesrelativepositionandnotdirection,butitshouldbenotedthattheuncertaintyrelationships depictedbyFigure1donotrepresentanyoneparticular method(direction,combination,orrelationshipofuncertaintygroupings)forthedevelopmentofatrip setpointorallowablevalue.Section4ofISA-S67.04-1994statesthatthesafetysignificanceofvarioustypesofsetpointsforsafety-relatedinstrumentationmaydiffer,andthusalessrigoroussetpointdeterminationmethodmaybe appliedforcertainfunctionalunitsandlimitingconditionsofoperation(LCOs).Asetpointmethodology canincludesuchagradedapproach.However,thegradingtechniquechosenbythelicenseeshouldbe consistentwiththestandardandshouldconsiderapplicableuncertaintiesregardlessofthesetpoint application.Additionally,theapplicationofthestandard,usinga"graded"approach,isalsoappropriate fornon-safetysysteminstrumentationformaintainingdesignlimitsdescribedintheTechnical Specifications.Examplesmayincludeinstrumentationreliedoninemergencyoperating procedures(EOPS),andformeetingapplicableLCOs,andformeetingthevariablesinRegulatoryGuide
10. General This guide was Issued after consideration of comments received from Copies of issued guides may be purchased at the current Government the public. Comments and suggestions for Improvements In these Printing Office price. Information on current GPO prices may be guides are encouraged at all times, and guides will be revised, as obtained by contacting the Superintendent of Documents, U.S. appropriate, to accommodate comments and to reflect new Informa- Government Printing Office. Post" Office Box 37082 Wasnhngton, tlon or experience.
1.97,"InstrumentationforLight-Water-CooledNuclearPowerPlantsToAssessPlantandEnvirons ConditionsDuringandFollowinganAccident." 3TheindustryconsensusstandardANSI/ANS-10.4-1987,"GuidelinesfortheVerificationandValidationofScientificandEngineeringComputerProgramsfortheNuclearIndustry,"provideshelpful informationonthequalificationofsetpointmethodologysoftware.ISA-S67.04-1982hasbeenusedbylicenseesforsetpointmethodologyandinstrumentdriftevaluations.ISA-S67.04-1994provideslimitedguidanceondriftevaluationsanduncertaintyterm developmentfortheevaluationofaninstrumentsurveillanceinterval.The
4 A D E B CSafetyLimitAnalyticalLimitNote:Thisfigureisintendedtoproviderelative positionandnotto implydirection.Allowancedescribedinparagraph4.3.1Allowancedescribedinparagraph4.3.1Regionwherechannelmaybedeterminedinoperable Plantoperatingmargin Regionofcalibrationtolerance(acceptableasleftcondition)
describedinparagraph4.3.1 A.B.C.


DC 20013-7082.
D.


telephone
E.AllowableValue(LSSS)TripSetpoint(LSSS)NormalFigure1.NuclearSafety-RelatedSetpointRelationships
(202)275-2060
5(ReproducedfromISA-67.04-1994)  
or (202)27h-2171.
6staffhasgenerallyaccepteddriftevaluationsbasedonstatisticalpredictiontechniques.However,significantvariabilityhasbeenobservedinlicensees'surveillanceintervalevaluationswithregardtodrift, setpointmethodology,andcompleteness.ThefollowingconcernswereidentifiedduringtheNRCstaff review,buttheyhavebeenresolvedduringthedevelopmentofISA-S67.04-1994.Limitedinstrumentdriftdatawereincludedinthelicenseesetpointstudy.Driftdataaccountforalldatapointsfromasurveillancecalibration(i.e.,nine-pointcheck)asindependentdata,butinadequatejustificationisprovidedforthisassumption.Driftdatapoints alsoincludedinterimcalibrations.Alargenumberofdatapointswasprovidedforalimitednumberofinstruments.Flawedoutlieranalysisresultedinvaliddatabeingremovedfromthedataset.Driftdependencyontimewasassumedtobenegligibleovertheintervalselected,andinadequatejustificationwasprovidedwhenextrapolatingtoanextendedsurveillanceinterval(e.g.,24


limit" as used in Figure 1 of the standard is the same as "trip setpoints" as used in the aforementioned STSs in that drift above the "upper setpoint limit" (standard)  
months).Setpointmethodologyassumesnormaldistributionofdatawhensuchanassumptionwasnot verified.Instrumentationevaluations(historical,maintenance,drift)wereincomplete.Driftprojections,includingthosebasedonregressionanalyses,maynotaccountforpenaltiesforuncertaintyprojection(extendedsurveillanceinterval-drift)beyondthetimerangeforthedata
or "trip setpoint" (STSs) requires readjustment.


Paragraph
collected.Instrumentapplicationandprocessorinstallationvariableswerenotevaluated.Theuncertaintiesassumedforinstrumentation,includingprimaryelements,weresubsequentlynotverifiedorcontrolledthroughsurveillancetesting,qualification,ormaintenanceprograms.Theacceptabilityofpoolinggenericdriftdatawithplant-specificdataorweighingthedataaccordingtothesourceofthedatawasnotjustified.Allavailableapplicabledatawerenotutilizedintheanalysis.Section4.3ofISA-S67.04-1994statesthatthelimitingsafetysystemsetting(LSSS)maybethetripsetpoint,anallowablevalue,orboth.Forthestandardtechnicalspecifications,thestaffdesignatedthe allowablevalueastheLSSS.Inassociationwiththetripsetpointandlimitingconditionsforoperation (LCOs),theLSSSestablishesthethresholdforprotectivesystemactiontopreventacceptablelimitsbeing exceededduringdesignbasisaccidents.TheLSSSthereforeensuresthatautomaticprotectiveactionwill correcttheabnormalsituationbeforeasafetylimitisexceeded.Alicensee,withjustification,may proposeanalternativeLSSSbasedonitsparticularsetpointmethodologyorlicense.Thestandardprovidesfortheaccountingofmeasurementandtestequipment(MTE)uncertainties,butMTEcriteriaarenotspecificallyidentifiedwithinthestandard.CriteriaXIandXIIinAppendixBto
4.3 of the standard specifies the methods for combining uncertainties in determining a trip set point and its allowable values. Typically, the NRC staff has accepted 95% as a probability limit for errors. That is, of the observed distribution of values for a particular error component in the empirical data base, 95% of the data points will be bounded by the value selected.
710CFRPart50providerequirementsforqualityregardingtesting.RegulatoryGuide1.118,"PeriodicTestingofElectricPowerandProtectionSystems," 3providesguidanceonperiodicsurveillancetesting.PartII,"MethodologiesfortheDeterminationofSetpointsfortheNuclearSafety-RelatedInstrumentation,"ofISA-S67.04-1994isnotaddressedbythisregulatoryguide.C.REGULATORYPOSITIONConformancewithPart1ofISA-S67.04-1994,"SetpointsforNuclearSafety-Related Instrumentation," 2withthefollowingexceptionsandclarifications,providesamethodacceptabletotheNRCstaffforsatisfyingtheNRC'sregulationsforensuringthatsetpointsforsafety-related instrumentationareestablishedandmaintainedwithinthetechnicalspecificationlimits.


If the data base follows a normal distribution, this corres ponds to an error distribution approximately equal to a "two sigma" value. Section 6 requires that "software qualification" be documented.
1.Section4ofISA-S67.04-1994specifiesthemethods,butnotthecriterion,forcombininguncertaintiesindeterminingatripsetpointanditsallowablevalues.The95/95tolerancelimitisan acceptablecriterionforuncertainties.Thatis,thereisa95%probabilitythattheconstructedlimitscontain
95%ofthepopulationofinterestforthesurveillanceintervalselected.


Although there is no generally accepted definition in the nuclear industry for software qualifica tion, the industry has used ANSI/IEEE-ANS-7-4.3.2-1982, "Application Criteria for Programmable Digital Computer Systems in Safety Systems of Nuclear Power Generating Stations," for verification and validation of computer software used in safety-related systems. Regulatory Guide 1.152, "Criteria for Programmable Digital Com puter System Software in Safety-Related Systems of Nuclear Power Plants," endorses this standard.
2.Sections7and8ofPart1ofISA-S67.04-1994referenceseveralindustrycodesandstandards.IfareferencedstandardhasbeenincorporatedseparatelyintotheNRC'sregulations,licensees andapplicantsmustcomplywiththatstandardassetforthintheregulation.Ifthereferencedstandardhas beenendorsedinaregulatoryguide,thestandardconstitutesamethodacceptabletotheNRCstaffof meetingaregulatoryrequirementasdescribedintheregulatoryguide.Ifareferencedstandardhasbeen neitherincorporatedintotheNRC'sregulationsnorendorsedinaregulatoryguide,licenseesandapplicants mayconsiderandusetheinformationinthereferencedstandardifappropriatelyjustified,consistentwith currentregulatorypractice.


Some of the considerations in documenting setpoint drift are (1) the degree of redundancy of the channels for which the allowable limits have been exceeded, (2) the type of instrument, including the instrument's designed accuracy, function, and plant identification number, (3) the allowable value in the technical specifi cations, (4) the "as left" setpoint from prior surveillance, (5) the measured setpoint, (6) the amount of adjustment in the reported occurrence and the current "as left" setpoint, and (7) the history of previous testing and the amount of any drift and adjustment in previous testing.C. REGULATORY
3.Section4.3ofISA-S67.04-1994statesthatthelimitingsafetysystemsetting(LSSS)maybemaintainedintechnicalspecificationsorappropriateplantprocedures.However,10CFR50.36states thatthetechnicalspecificationswillincludeitemsinthecategoriesofsafetylimits,limitingsafetysystem settings,andlimitingcontrolsettings.Thus,theLSSSmaynotbemaintainedinplantprocedures.Rather, theLSSSmustbespecifiedasatechnical-specification-definedlimitinordertosatisfytherequirementsof
POSITION ISA-$67.04-1982, "Setpoints for Nuclear Safety Related Instrumentation Used in Nuclear Power Plants,' establishes requirements acceptable to the NRC staff for ensuring that instrument setpoints in safety-related systems are initially within and remain within the technical specification limits. The last section of ISA S67.04-1982 lists additional standards that are referenced in other sections of the standard.
10CFR50.36.TheLSSSshouldbedevelopedinaccordancewiththesetpointmethodologysetforthin thestandard,withtheLSSSlistedinthetechnicalspecifications.


Those referenced standards not endorsed by a regulatory guide (or incor porated into the regulations)
4.ISA-S67.04-1994providesadiscussiononthepurposeandapplicationofanallowablevalue.Theallowablevalueisthelimitingvaluethatthetripsetpointcanhavewhentestedperiodically, beyondwhichtheinstrumentchannelisconsideredinoperableandcorrectiveactionmustbetakenin accordancewiththetechnicalspecifications.Theallowablevaluerelationshiptothesetpointmethodology andtestingrequirementsinthetechnicalspecificationsmustbedocumented.
also contain valuable information and, if used, should be used in a manner consistent with current regulations.


==D. IMPLEMENTATION==
==D. IMPLEMENTATION==
The purpose of this section is to provide information to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.  Except in those cases in which the applicant or li censee proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the methods described in this guide will be used by the NRC staff in the evaluation of instru ment setpoints for safety-related systems with respect to the technical specification limits for the following nuclear power plants: 1. Plants for which the constructi6n permit is issue after February 1986.  2. Plants for which the operating license applica tion is docketed 6 months or more after February 1986.  3. Plants for which the applicant or licensee vol untarily commits to the provisions of this guide.1.105-2 VALUE/IMPACT
ThepurposeofthesectionistoprovideinformationtoapplicantsandlicenseesregardingtheNRCstaff'splansforusingthisregulatoryguide.
STATEMENT
 
===1. BACKGROUND ===
The most common cause of a setpoint in a safety related system being out of compliance with plant .technical specifications has been the failure to allow for a sufficient margin to account for instrument inaccura cies, expected environmental drift, and minor calibration variations.
 
For example, in some cases, the trip setpoint selected was numerically equal to the allowable value and stated as an "absolute value," thus leaving no apparent margin for drift. In other cases, the trip setpoint was so close to the upper or lower limit of the range of the instrument that instrument drift placed the setpoint beyond the range of the instrument, thus nullifying the trip function.
 
Other general causes for a setpoint being out of conformity with the technical specifications have been instrument design inadequacies and questionable calibration procedures.
 
Revision I to Regulatory Guide 1.105, "Instrument Setpoints," was issued in November 1976 in response to the large number of instances reported in Licensee Event Reports (LERs) of setpoints drifting outside the limits specified in the technical specifications.
 
Revision I provided general guidance for (1) specifying setpoints (by considering instrument drift, accuracy, and range) and (2) having a securing device for the set point adjustment mechanism.
 
The method described in Revision I to Regulatory Guide 1.105 has been incorporated into an Instrument Society of America Standard, ISA-$67.04-1982, "Set points for Nuclear Safety-Related Instrumentation Used in Nuclear Power Plants." Revision 2 to Regulatory Guide 1.105 was developed to use the guidance of ISA-$67.04-1982.
 
This revision provides more specific guidance on establishing and maintaining setpoints in response to the needs that were apparent from (1) a continuing large number of reportable occurrences and (2) the licensing review of methodology for specifying allowable values and trip setpoints.
 
2. VALUE/IMPACT
ASSESSMENT
2.1 General ISA-S67.04-1982 is considered state-of-the-art meth odology for specifying and reviewing technical specifica tions on allowable values and trip setpoints, and mem bers of the industry have incorporated this standard into their internal procedures.
 
Further, paragraphs
50.73(a) and (b) of 10 CFR Part 50 define when an LER is required and what is to be included in an LER, respectively.


2.2 Value The value to NRC operations and industry- is that there would be (1) a systematic method for specifying and reviewing technical specifications on allowable values and trip setpoints, (2) more sophisticated methods for specifying technical specifications, (3) a reduction in setpoint readjustments, (4) less chance for unwarranted reactor shutdown, and (5) fewer LERs and other report able occurrences from the allowable limits of setpoints being exceeded.
8ExceptinthosecasesinwhichanapplicantorlicenseeproposesanacceptablealternativemethodforcomplyingwithspecifiedportionsoftheNRC'sregulations,themethodsdescribedinthisguidewillbe usedintheevaluationofsubmittalsinconnectionwithapplicationsforconstructionpermits,operating licenses,andcombinedlicenses.Itwillalsobeusedtoevaluatesubmittalsfromoperatingreactor licenseeswhovoluntarilyproposetoinitiatesystemmodificationsifthereisaclearnexusbetweenthe proposedmodificationsandthisguidance.


2.3 Impact The impact would be minimal as ISA-$67.04-1982 represents current industry practice that has been codified in a national consensus standard.1.105-3 UNITED STATES NUCLEAR REGULATORY
9VALUE/IMPACTSTATEMENTAdraftvalue/impactstatementwaspublishedwiththedraftproposedRevision3ofthisguidewhenitwaspublishedforpubliccomment(DG-1045,October1996).Nochangeswerenecessary,soa separatevalue/impactstatementforthefinalguidehasnotbeenprepared.Acopyofthedraftvalue/impact statementisavailableforinspectionorcopyingforafeeintheNRC'sPublicDocumentRoomat2120L
COMMISSION
StreetNW.,Washington,DCundertaskDG-1045.}}
WASHINGTON, D.C. 20555 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE, $300 FIRST CLASS MAIL POSTAGE & FEES PAID USNNCI WASH. D.C.  PERMIT No. G-67}}


{{RG-Nav}}
{{RG-Nav}}

Revision as of 08:56, 21 September 2018

Setpoints for Safety-Related Instrumentation
ML993560062
Person / Time
Issue date: 12/31/1999
From:
Office of Nuclear Regulatory Research
To:
Aggarwal S K (301)415-6005
References
RG-1.105, Rev. 3
Download: ML993560062 (7)
v • d • e


1ForthefulltextoftheGeneralDesignCriteriaandothersectionsoftheregulationscitedinthisguide,see10CFRPart50,"DomesticLicensingofProductionandUtilizationFacilities."RegulatoryguidesareissuedtodescribeandmakeavailabletothepublicsuchinformationasmethodsacceptabletotheNRCstaffforimplementingspecificpartsoftheNRC'sregulations,techniquesusedbythestaffinevaluatingspecificproblemsorpostulatedaccidents,anddataneededbytheNRCstaffinitsreviewofapplicationsforpermitsandlicenses.Regulatoryguidesarenotsubstitutesforregulations,andcompliancewiththemisnotrequired.MethodsandsolutionsdifferentfromthosesetoutintheguideswillbeacceptableiftheyprovideabasisforthefindingsrequisitetotheissuanceorcontinuanceofapermitorlicensebytheCommission.Thisguidewasissuedafterconsiderationofcommentsreceivedfromthepublic.Commentsandsuggestionsforimprovementsintheseguidesareencour agedatalltimes,andguideswillberevised,asappropriate,toaccommodatecommentsandtoreflectnewinformationorexperience.Writtencommentsmayb esubmittedtotheRulesandDirectivesBranch,ADM,U.S.NuclearRegulatoryCommission,Washington,DC20555-0001.Regulatoryguidesareissuedintenbroaddivisions:1,PowerReactors;2,ResearchandTestReactors;3,FuelsandMaterialsFacilities;4,EnvironmentalandSiting;5,MaterialsandPlantProtection;6,Products;7,Transportation;8,OccupationalHealth;9,AntitrustandFinancialReview;and10,Ge neral.Singlecopiesofregulatoryguides(whichmaybereproduced)maybeobtainedfreeofchargebywritingtheDistributionServicesSection,U.S.Nuclea rRegulatoryCommission,Washington,DC20555-0001,orbyfaxto(301)415-2289,orbyemailtoDISTRIBUTION@NRC.GOV.Manyregulatoryguidesare alsoavailableontheinternetatNRC'shomepageat<WWW.NRC.GOV>.U.S.NUCLEARREGULATORYCOMMISSIONRevision3December1999 REGULATORY

GUIDEOFFICEOFNUCLEARREGULATORYRESEARCHREGULATORYGUIDE1.105(DraftwasDG-1045)SETPOINTSFORSAFETY-RELATEDINSTRUMENTATION

A. INTRODUCTION

Criterion13,"InstrumentationandControl," 1ofAppendixA,"GeneralDesignCriteriaforNuclearPowerPlants,"to10CFRPart50,"DomesticLicensingofProductionandUtilizationFacilities,"requires, amongotherthings,thatinstrumentationbeprovidedtomonitorvariablesandsystemsandthatcontrolsbe providedtomaintainthesevariablesandsystemswithinprescribedoperatingranges.Criterion20,"ProtectionSystemFunctions,"ofAppendixAto10CFRPart50requires,amongotherthings,thattheprotectionsystembedesignedtoinitiateoperationofappropriatesystemstoensurethat specifiedacceptablefueldesignlimitsarenotexceeded.Paragraph(c)(1)(ii)(A)of§50.36,"TechnicalSpecifications,"of10CFRPart50requires,inpart,that,wherealimitingsafetysystemsettingisspecifiedforavariableonwhichasafetylimithasbeenplaced, thesettingbesochosenthatautomaticprotectiveactionwillcorrecttheabnormalsituationbeforeasafety limitisexceeded.Italsorequires,amongotherthings,thatthelicenseenotifytheNRCifthelicensee determinesthatanautomaticsafetysystemdoesnotfunctionasrequired.Thelicenseeisrequiredtothen reviewthematterandrecordtheresultsofthereview.

2CopiesmaybeobtainedfromtheInstrumentSocietyofAmerica,67AlexanderDrive,ResearchTrianglePark,NC

20779.2ThisguidedescribesamethodacceptabletotheNRCstaffforcomplyingwiththeNRC'sregulationsforensuringthatsetpointsforsafety-relatedinstrumentationareinitiallywithinandremain withinthetechnicalspecificationlimits.TheguideisbeingrevisedtoendorsePartlofISA-S67.04-1994,

"SetpointsforNuclearSafety-RelatedInstrumentation." 2Thisstandardprovidesabasisforestablishingsetpointsfornuclearinstrumentationforsafetysystemsandaddressesknowncontributingerrorsinthe

channel.Theinformationcollectionscontainedinthisregulatoryguidearecoveredbytherequirementsin10CFRPart50,whichwereapprovedbytheOfficeofManagementandBudget,approvalnumber3150-

0011.TheNRCmaynotconductorsponsor,andapersonisnotrequiredtorespondto,acollectionof informationunlessitdisplaysacurrentlyvalidOMBcontrolnumber.

B. DISCUSSION

Instrumentsetpointuncertaintyallowancesandsetpointdiscrepancieshaveledtoanumberofoperationalproblems.Operatingexperienceindicatesthatsetpointsforsafety-relatedinstrumentationmay allowplantstooperateoutsidethelimitingconditionsofoperationspecifiedintheirtechnical specifications.Licenseeshavediscoveredconflictsbetweenexistingsetpointsandengineering calculations.Thecausesforthesesetpointdiscrepancieswereproblemswithindustrypracticesthatledto errorsincalibrationproceduresandalackofunderstandingoftherelationshipofthesetpointtothe allowablevalue.Additionalproblemsnotedincludedvaryingsetpointmethodologiesforengineering calculations,alackofaconsistentdefinitionofallowablevaluebetweendifferentsetpointmethodologies, andimproperunderstandingoftherelationshipoftheallowablevaluetoearliersetpointterminology, procedures,andoperabilitycriteria.Furtherproblemswerenotedwhenprocedures(thesetpointprocess)

(1)failedtoprovideanadequatemarginbetweentheinstrumentas-leftcriteriaandthevalues(tripset pointorallowablevalues)requiredperthetechnicalspecifications,(2)didnotalwaysreflectcurrent designcriteria,and(3)didnotensurethatrevisedinstrumentloopswereverifiedtotheoriginaldesign requirementsorthatinstrumentmodificationswereevaluatedfortheireffectonsetpointcalculations.It hasalsobeennotedthatlicenseesdonottypicallyverifywhethersetpointcalculationdriftassumptions haveremainedvalidforthesystemsurveillanceinterval.ISA-S67.04wasrevisedin1987toprovideclarificationandtoreflectindustrypractice.Theterm"tripsetpoint"wasmadeconsistentwiththeterminologyusedbytheNRCstaff.Thestandardwasrevisedfurtherin1994.Theeffectsofuncertaintyallowancesanddiscrepanciesinsetpoints,alongwithoperationalexperience,wereappropriatelyaddressedduringthisrevisionofISA-

S67.04.ThisrevisionofthestandardalsoreflectstheImprovedTechnicalSpecificationprogram(a cooperativeeffortbetweenindustryandtheNRCstaff)andreflectcurrentindustrypractice.Thisstandard providesabasisforestablishingsetpointsfornuclearinstrumentationforsafetysystemsandaddresses knowncontributingerrorsinaparticularchannelfromtheprocess(includingtheprimaryelementand sensor)throughandincludingthefinalsetpointdevice.Theterm"tripsetpoint"isretainedinISA-S67.04-1994.However,Figure1inISA-S67.04-1994(forconvenience,thisfigurehasbeenreproducedasFigure1inthisguide)hasbeenrevisedtodepict region"E,""aregionofcalibrationtolerance."Thecalibrationtoleranceuncertaintiesdepictedbyregion

3Singlecopiesofregulatoryguides,bothactiveanddraft,maybeobtainedfreeofchargebywritingtheOfficeofAdministration,Attn:ReproductionandDistributionServicesSection,U.S.NuclearRegulatoryCommission,Washington,DC20555,orbyfaxto(301)415-2289,orbyemailto<DISTRIBUTION@NRC.GOV>.CopiesarealsoavailableforinspectionorcopyingforafeefromtheNRCPublicDocumentRoomat2120LStreetNW.,

Washington,DC;thePDR'smailingaddressisMailStopLL-6,Washington,DC20555;telephone(202)634-3273;

fax(202)634-3343.

3"E"shouldbedefinedandaccountedforinthelicensee'ssetpointmethodology.Atripsetpointvalueidentifiedtobeoutsideregion"E"regardlessofdirectionrequiresreadjustmenttosatisfythesetpoint methodologyanduncertaintiesidentifiedinFigure1(acceptableas-leftcondition).Itshouldbenotedthat thisstandarddoesnotdefine"nominal"tripsetpoint.ThetripsetpointasdepictedinFigure1isconsistent withtheterm"nominal"tripsetpointasshownaboutadefinedcalibrationtoleranceband.Figure1ofthestandardprovidessetpointrelationshipsfornuclearsafety-relatedsetpoints.Thefiguredenotesrelativepositionandnotdirection,butitshouldbenotedthattheuncertaintyrelationships depictedbyFigure1donotrepresentanyoneparticular method(direction,combination,orrelationshipofuncertaintygroupings)forthedevelopmentofatrip setpointorallowablevalue.Section4ofISA-S67.04-1994statesthatthesafetysignificanceofvarioustypesofsetpointsforsafety-relatedinstrumentationmaydiffer,andthusalessrigoroussetpointdeterminationmethodmaybe appliedforcertainfunctionalunitsandlimitingconditionsofoperation(LCOs).Asetpointmethodology canincludesuchagradedapproach.However,thegradingtechniquechosenbythelicenseeshouldbe consistentwiththestandardandshouldconsiderapplicableuncertaintiesregardlessofthesetpoint application.Additionally,theapplicationofthestandard,usinga"graded"approach,isalsoappropriate fornon-safetysysteminstrumentationformaintainingdesignlimitsdescribedintheTechnical Specifications.Examplesmayincludeinstrumentationreliedoninemergencyoperating procedures(EOPS),andformeetingapplicableLCOs,andformeetingthevariablesinRegulatoryGuide

1.97,"InstrumentationforLight-Water-CooledNuclearPowerPlantsToAssessPlantandEnvirons ConditionsDuringandFollowinganAccident." 3TheindustryconsensusstandardANSI/ANS-10.4-1987,"GuidelinesfortheVerificationandValidationofScientificandEngineeringComputerProgramsfortheNuclearIndustry,"provideshelpful informationonthequalificationofsetpointmethodologysoftware.ISA-S67.04-1982hasbeenusedbylicenseesforsetpointmethodologyandinstrumentdriftevaluations.ISA-S67.04-1994provideslimitedguidanceondriftevaluationsanduncertaintyterm developmentfortheevaluationofaninstrumentsurveillanceinterval.The

4 A D E B CSafetyLimitAnalyticalLimitNote:Thisfigureisintendedtoproviderelative positionandnotto implydirection.Allowancedescribedinparagraph4.3.1Allowancedescribedinparagraph4.3.1Regionwherechannelmaybedeterminedinoperable Plantoperatingmargin Regionofcalibrationtolerance(acceptableasleftcondition)

describedinparagraph4.3.1 A.B.C.

D.

E.AllowableValue(LSSS)TripSetpoint(LSSS)NormalFigure1.NuclearSafety-RelatedSetpointRelationships

5(ReproducedfromISA-67.04-1994)

6staffhasgenerallyaccepteddriftevaluationsbasedonstatisticalpredictiontechniques.However,significantvariabilityhasbeenobservedinlicensees'surveillanceintervalevaluationswithregardtodrift, setpointmethodology,andcompleteness.ThefollowingconcernswereidentifiedduringtheNRCstaff review,buttheyhavebeenresolvedduringthedevelopmentofISA-S67.04-1994.Limitedinstrumentdriftdatawereincludedinthelicenseesetpointstudy.Driftdataaccountforalldatapointsfromasurveillancecalibration(i.e.,nine-pointcheck)asindependentdata,butinadequatejustificationisprovidedforthisassumption.Driftdatapoints alsoincludedinterimcalibrations.Alargenumberofdatapointswasprovidedforalimitednumberofinstruments.Flawedoutlieranalysisresultedinvaliddatabeingremovedfromthedataset.Driftdependencyontimewasassumedtobenegligibleovertheintervalselected,andinadequatejustificationwasprovidedwhenextrapolatingtoanextendedsurveillanceinterval(e.g.,24

months).Setpointmethodologyassumesnormaldistributionofdatawhensuchanassumptionwasnot verified.Instrumentationevaluations(historical,maintenance,drift)wereincomplete.Driftprojections,includingthosebasedonregressionanalyses,maynotaccountforpenaltiesforuncertaintyprojection(extendedsurveillanceinterval-drift)beyondthetimerangeforthedata

collected.Instrumentapplicationandprocessorinstallationvariableswerenotevaluated.Theuncertaintiesassumedforinstrumentation,includingprimaryelements,weresubsequentlynotverifiedorcontrolledthroughsurveillancetesting,qualification,ormaintenanceprograms.Theacceptabilityofpoolinggenericdriftdatawithplant-specificdataorweighingthedataaccordingtothesourceofthedatawasnotjustified.Allavailableapplicabledatawerenotutilizedintheanalysis.Section4.3ofISA-S67.04-1994statesthatthelimitingsafetysystemsetting(LSSS)maybethetripsetpoint,anallowablevalue,orboth.Forthestandardtechnicalspecifications,thestaffdesignatedthe allowablevalueastheLSSS.Inassociationwiththetripsetpointandlimitingconditionsforoperation (LCOs),theLSSSestablishesthethresholdforprotectivesystemactiontopreventacceptablelimitsbeing exceededduringdesignbasisaccidents.TheLSSSthereforeensuresthatautomaticprotectiveactionwill correcttheabnormalsituationbeforeasafetylimitisexceeded.Alicensee,withjustification,may proposeanalternativeLSSSbasedonitsparticularsetpointmethodologyorlicense.Thestandardprovidesfortheaccountingofmeasurementandtestequipment(MTE)uncertainties,butMTEcriteriaarenotspecificallyidentifiedwithinthestandard.CriteriaXIandXIIinAppendixBto

710CFRPart50providerequirementsforqualityregardingtesting.RegulatoryGuide1.118,"PeriodicTestingofElectricPowerandProtectionSystems," 3providesguidanceonperiodicsurveillancetesting.PartII,"MethodologiesfortheDeterminationofSetpointsfortheNuclearSafety-RelatedInstrumentation,"ofISA-S67.04-1994isnotaddressedbythisregulatoryguide.C.REGULATORYPOSITIONConformancewithPart1ofISA-S67.04-1994,"SetpointsforNuclearSafety-Related Instrumentation," 2withthefollowingexceptionsandclarifications,providesamethodacceptabletotheNRCstaffforsatisfyingtheNRC'sregulationsforensuringthatsetpointsforsafety-related instrumentationareestablishedandmaintainedwithinthetechnicalspecificationlimits.

1.Section4ofISA-S67.04-1994specifiesthemethods,butnotthecriterion,forcombininguncertaintiesindeterminingatripsetpointanditsallowablevalues.The95/95tolerancelimitisan acceptablecriterionforuncertainties.Thatis,thereisa95%probabilitythattheconstructedlimitscontain

95%ofthepopulationofinterestforthesurveillanceintervalselected.

2.Sections7and8ofPart1ofISA-S67.04-1994referenceseveralindustrycodesandstandards.IfareferencedstandardhasbeenincorporatedseparatelyintotheNRC'sregulations,licensees andapplicantsmustcomplywiththatstandardassetforthintheregulation.Ifthereferencedstandardhas beenendorsedinaregulatoryguide,thestandardconstitutesamethodacceptabletotheNRCstaffof meetingaregulatoryrequirementasdescribedintheregulatoryguide.Ifareferencedstandardhasbeen neitherincorporatedintotheNRC'sregulationsnorendorsedinaregulatoryguide,licenseesandapplicants mayconsiderandusetheinformationinthereferencedstandardifappropriatelyjustified,consistentwith currentregulatorypractice.

3.Section4.3ofISA-S67.04-1994statesthatthelimitingsafetysystemsetting(LSSS)maybemaintainedintechnicalspecificationsorappropriateplantprocedures.However,10CFR50.36states thatthetechnicalspecificationswillincludeitemsinthecategoriesofsafetylimits,limitingsafetysystem settings,andlimitingcontrolsettings.Thus,theLSSSmaynotbemaintainedinplantprocedures.Rather, theLSSSmustbespecifiedasatechnical-specification-definedlimitinordertosatisfytherequirementsof

10CFR50.36.TheLSSSshouldbedevelopedinaccordancewiththesetpointmethodologysetforthin thestandard,withtheLSSSlistedinthetechnicalspecifications.

4.ISA-S67.04-1994providesadiscussiononthepurposeandapplicationofanallowablevalue.Theallowablevalueisthelimitingvaluethatthetripsetpointcanhavewhentestedperiodically, beyondwhichtheinstrumentchannelisconsideredinoperableandcorrectiveactionmustbetakenin accordancewiththetechnicalspecifications.Theallowablevaluerelationshiptothesetpointmethodology andtestingrequirementsinthetechnicalspecificationsmustbedocumented.

D. IMPLEMENTATION

ThepurposeofthesectionistoprovideinformationtoapplicantsandlicenseesregardingtheNRCstaff'splansforusingthisregulatoryguide.

8ExceptinthosecasesinwhichanapplicantorlicenseeproposesanacceptablealternativemethodforcomplyingwithspecifiedportionsoftheNRC'sregulations,themethodsdescribedinthisguidewillbe usedintheevaluationofsubmittalsinconnectionwithapplicationsforconstructionpermits,operating licenses,andcombinedlicenses.Itwillalsobeusedtoevaluatesubmittalsfromoperatingreactor licenseeswhovoluntarilyproposetoinitiatesystemmodificationsifthereisaclearnexusbetweenthe proposedmodificationsandthisguidance.

9VALUE/IMPACTSTATEMENTAdraftvalue/impactstatementwaspublishedwiththedraftproposedRevision3ofthisguidewhenitwaspublishedforpubliccomment(DG-1045,October1996).Nochangeswerenecessary,soa separatevalue/impactstatementforthefinalguidehasnotbeenprepared.Acopyofthedraftvalue/impact statementisavailableforinspectionorcopyingforafeeintheNRC'sPublicDocumentRoomat2120L

StreetNW.,Washington,DCundertaskDG-1045.


Retrieved from "https://kanterella.com/w/index.php?title=Regulatory_Guide_1.105&oldid=1063227"