ML17256A352

Forwards Status Rept Re Unresolved Safety Issues,Per NRC 820617 Request.Info Includes Description of Problem Based on NRC Documentation

ML17256A352
Person / Time
Site:	Ginna
Issue date:	10/19/1982
From:	MAIER J E ROCHESTER GAS & ELECTRIC CORP.
To:	CRUTCHFIELD D Office of Nuclear Reactor Regulation
References
TASK-***, TASK-OR NUDOCS 8210250275
Download: ML17256A352 (87)

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REGULATURYI'RHATIONDISTRIBUTIONSYSJ'RIDS)fh-gA>>gACCESSIONNBR'8210250275OVC~DATE'2/10/19NOTARIZED'ESDOCKETFACIL:50244RobertEmmetGinnaNuclearPlant<UnitiiRochesterG05000244AUTHINANEAUTHORAFFILIATIONHAIERiJ~E>>RochesterGasKElectricCorp'ECIP,NAHERECIPIENTAFFILIATIONCRUTCWFIELDrDOperat)ngReactorsBranch5

SUBJECT:

ForwardsstatusreptreunresolvedsafetyissuesiperNRC820617request~InfoincludesdescriptionofproblembasedonNRCdocumentation.DISTRIBUTIONCODE:A001S.COPIESRECEIVED:LTRENCLSIZE:TITLE;ORSubmittal:GeneralDistributionNOTES:NRR/DL/SEPicy'5000244RECIPIENTIDCODE/NAHENRRORB5BC01INTERVAL:ELD/WDS4NRR/DLDIRNRR/DSI/RABRGN1COPIESLTTRENCL7710111111RECIPIENTIDCODE/NAHENRR/DWFSDEPY08NABEGFLE04COPIESLTTRENCL11101,1EXTERNALSACRSNRCPDRNTISNOTES:0902e1111LPDR-NSIC0305111TOTALNUHBEROFCOPIESREQUIREDTTR25ENCL23 Ir)."(!'Tzq.'~p~i()tp~6A(>r(plI~lIxlII0o(~9>i~>Af<1(>Igcp,Ii'FI,I'.p)'IIIIi,]"lfpzq"l>>8'l8cz39>>i71~3cziIw;pfII.zl'pl,frfc~~~'<<.I'('>(iI"lII)'sp~'fI>><Jr'I>}'IO'3q8)LP~fY30fr(ppvfc)')'pcl(P'P'0J'}i9'1I'f)'fc'I1yP'II)9~6cc~}9Igg'1~Ifcp(lcpr'fIr1p(.r)czl9(>'spIoArc)f04NQgrp>9'15J(pI(>4,(~orf<.fr(~(},pa,ii}..pi~,((cp4$T~...4I)ictrlT.I:,Ifv'IIII'I~"fT<<pa"g('cpA;,f<Iz,).'"1fII<>JHfc,IIcfc}roccfr'of.,r'>la~vnv(p;ledIr"pep(.Ilp:3I'Il'II>>pz4(p0tp(p(z,yof(I,)clX,Jc,chpfk)~(:c,I'tIp'IP3I(II),I)'ppcsIJ1'~:lk'Ig1t}ll,'I~IAvv~l(i~'IIcpII..I>><<SH>II,'tNF)p'I(I'"lpga(P(II>q),zI4i'.rocl3fI.i.I'IwIc5'IlIIphyllpgIp(~IJI(zIlcpp(4zJ'('fi"'/(T}lI

~snzprriiviznIIISt<uuenzxzrzrzraw'OCHESTERGASANDELECTRICCORPORATION~89EASTAVENUE,ROCHESTER,N.Y.14649JOHNE.MAIGRVicePresidentTKLKPHONKARKAcooK7le546-2700October19,1982DirectorofNuclearReactorRegulationAttention:Mr.DennisM.Crutchfield,ChiefOperatingReactorsBranchNo.5U.S.NuclearRegulatoryCommissionWashington,D.C.20555

Subject:

UnresolvedSafetyIssueStatusR.E.GinnaNuclearPowerPlantDocketNo.50-244

DearMr.Crutchfield:

ThisletterandtheattachedreportarebeingprovidedinresponsetoaletterofJune17,1982fromGusC.LainastoJohnE.Maier,requestingthestatusofapplicableUnresolvedSafetyIssues(USIs)fortheR.E.GinnaNuclearPowerPlant.Inthatletter,theNRCrequestedthatthefollowinginformationbeprovidedrelativetoeachUnresolvedSafetyIssue:(1)hastheissuebeenresolvedatGinna(2)ifso,howhasitbeenresolved;and(3)iffullresolutionhasnotoccurred(includingimplementationofnecessaryhardware,procedures,etc.),whatinterimmeasureshavebeentakentoassurethatcontinuedoperationwouldnotposeanunduerisktothepublic.TheattachmenttothisletteraddresseseachUSIidentifiedinMr.Lainas'etter.ForeachUSI,adescriptionoftheproblembasedonNRCdocumentationisprovidedalongwiththeRG&Estatus.I

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tROCHESTERGASANDELECTICCORP.ober19,182Mr.DennisM.CrutchfieldSHEETNO.WetrustthatourresponsestotheseissuesaresufficienttobeusedintheNRCstaff'sSafetyEvaluationReportregardingtheconversionoftheProvisionalOperatingLicenseforGinnatoaFull-TermOperatingLicense.Verytrulyyours,JohnE.MaierAttachmentSwornandsubscribedtomeonthis19thdayofctobr1982LYNNI.HAUCKNOTARYPUBLIC,StateofII.Y.,MonrooCountyMyCommissionExpiresMarch3019.8 UnresolvedSafetyIssuesStatusReportR.E.GinnaNuclearPowerPlantDocketNo.50-244October19,1982 UnresolvedSafetIssueA-1WaterHammerDescriptionofProblem:Waterhammeroccurswhentheinertialpropertiesofapipingsystemfluidarerapidlyaltered,causingthedevelopmentofpotentiallydamagingpressurepulses.Since1971therehavebeennumerousincidentsinvolvingwaterhammersinBWRsandPWRs.Waterhammershaveinvolvedsteamgeneratorfeedringsandpiping,theRHRsystem,ECCsystems,andcontainmentspray,servicewater,feedwaterandsteamlines.Theincidentshavebeenattri-butedtosuchcausesasrapidcondensationofsteampockets,steamdrivenslugsofwater,pumpstartupwithpartiallyemptylines,andrapidvalvemotion.Mostofthedamagereportedhasbeenrelativelyminor,involvingpipehangersandrestraints;however,therehavebeenseveralincidentswhichhaveresultedinpipingandvalvedamage.Noneoftheseincidentshaveinvolvedthereleaseofradioactivitytotheenvirons.RG6EStatus:TheprimaryobjectiveofthistaskwastoresolvethepotentialforwaterhammerdamagingthePWRsteamgeneratorsandfeedwaterlines.AnumberoffactorsatGinnaStationreducethelikelihoodofsteamgeneratorwaterhammers,suchaslimitingauxiliaryfeedwaterflowtolessthan150gpmwhensteamgeneratorlevelsarelowandthereisnosafetyrequirementformorefeedwater; 0~I~Ig~II automaticstartofauxiliaryfeedwateronlossofallfeedwater,lossofoffsitepower,lowlowlevelinanyonesteamgenerator,andsafetyinjection;andthefactthatthereisonlyashortlengthoffeedwaterpipingbetweenasteamgeneratoranditsloopseal.Thelikelihoodofwaterhammerwasfurtherreducedbyinstallationin1979of"J"tubesontheGinnasteamgeneratorfeedrings.TheNRC'sDecember20,1979SafetyEvaluationReportforGinnarelativetosteamgeneratorwaterhammerconcludedthatthemeansforreducingthepotentialforsteamgeneratorwaterhammeratthisfacility[Ginna]areadequate...andnofurtheractionisrequiredofthelicenseewithregardtosteamgeneratorwaterhammer."Noproblemsassociatedwithwaterhammerinotherfluidsystemlineshavebeenexperienced,orareanticipated,atGinna.BasedontheGinnadesign,operatingexperience,andoperatingprocedures,RG6EconsidersthatthisissueisproperlyaddressedfortheGinnaplant,andthat.operationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.2

~~IIl~'I'l 1~~UnresolveSafetIssueA-2AsmmetricBlowdownLoadsontheReactorCoolantSstemDescriptionofProblem:IntheeventofapostulatedLOCAatareactorvesselnozzle,asymmetricloadingonthereactorvessel,itssupports,andinternalscouldresultfromtransientdifferentialpressuresinthereactorcavity.SuchloadingcouldpotentiallycausedamagetotheECCSlines,controlrods,otherreactorcoolantsystemcomponents,andthefuelassemblies.RG6EStatus:RG&EisanactiveparticipantintheWestinghouseA-2OwnersGroupaddressingthisissue.;ThefollowingWestinghouseTopicalReports,whichareapplicabletoGinna,havebeensubmittedtoJI1theNRC,andarecurrentlybeingevaluatedbytheNRCstaffandtheircontractorEG6G:WCAP9558throughRev.2,5/82WCAP9787throughRev.1,5/81WCAP97496/80WCAP95706/80and10/79WCAP97486/80WCAP96622/80,1/80WCAP962811/79 t~~~y7 NUREG-0609,"AsymmetricBlowdownLoadsorPWRPrimarySystems,ResolutionofGenericTaskActionPlanA-2,"January1981,hasbeenpublishedbytheNRC.ThisdocumentdefinesimplementationcriteriadevelopedaspartofA-2.AlthoughnotyetissuedbytheNRC,RG&EexpectsthatafinalacceptanceoftheWestinghouseA-2OwnersGroupandRG&EanalyseswillcompleteallopenissuesrelatedtoA-2.TheanalyseshavealreadybeendiscussedwiththeAdvisoryCommitteeonReactorSafeguards.BasedontheanalysesperformedaspartoftheWestinghouseA-2OwnersGroup,RG&EconsidersthattheissueofAsymmetricBlowdownLoadshasbeenadequatelyaddressedfortheGinn'aplant,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.

IIIpI)1Js~If,'1If UnresolvedSafetIssueA-3ilSteamGeneratorTubeInteritDescriptionofProblem:Thisissueaddressesthecapabilityofsteamgeneratortubestomaintaintheirintegrityduringnormaloperationandunderaccidentconditions,,withadequatesafety.margins.PWRsteamfIgeneratortubinginsomeplantshasexperiencedtubewallthinning(wastage),intergranul'aZattack,stress-corrosioncracking,anddenting.RG&EStatus:RochesterGasandElectricreplacedtheoriginalphosphatesecondarysidewaterchemistrytreatmentwithanall-volatiletreatmentinNovember1974andaddedfullflowcondensatepolishingdemineralizersin1978.Atpresent,lessthan5%ofthetubesineachsteamgeneratorhavebeenplugged.Inaddition,21tubesintheBsteamgeneratorhavebeensleeved.Theprimaryreasonsfortuberepairhavebeenwastageandcreviceintergranularattack.Asaresultofthechangeinchemistry,wastagenolongerappearstobeoccurring.RGEE'spresentprogramofsteamgeneratortubeinspectionsprovidesforeddycurrenttestsofthetubes,tubesheetwaterlancing,andcrevicecleaningifdeterminedtobenecessary.Further,RG&Ehasproposedasleevingprogramtoinstallsleeves asapreventivemeasureonthosesteamgeneratortubesconsideredmostsusceptibletocreviceintergranularattack.OnJanuary25,1982,GinnaStationexperiencedasteamgeneratortuberupture.Thedescriptionoftheevent,andtherestartSafetyEvaluationReport,areNUREG-0909andNUREG-0916,respectively.Basedontheinserviceinspectionandtestingbeingper-formedontheGinnasteamgenerators,theexistenceofthemetalimpactmonitoringsysteminstalledonthesteamgenerators,andtheproposedpreventivesleevingprogram,RG6EconsidersthatthesubjectofSteamGeneratorTubeIntegrityisbeingadequatelyaddressedfortheGinnaplant,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.

UnresolvedSafetIssueA-9AnticiatedTransientsWithoutScram(ATWS)DescriptionofProblem:Duringoperationofanuclearpowerplant,keyparametersaremonitoredandusedtoactuatesafetysystemsthatinitiateshutdown(SCRAM)ofthereactor.Foranumberofyearstherehasbeenconcernthat,followingatemporarilyabnormaloperationcondition,.or!anticipatedtransient,".afailurecouldoccurinfJt1'YV',1thesystemsrequire'd'oinsert,thecontrolrodsintothereactor,Jandaresultantscrammightnotoccur.Failuretoscramduringorfollowingananticipatedtransient,'wouldincreasetheseverityofthetransient,andcouldcausefueldamage.RGGEStatus:TheTechnicalReportonAnticipatedTransientsWithoutScramforWater-CooledPowerReactors,WASH-1270,discussedtheprob-abilityofanATWSeventandanappropriatesafetyobjectivefortheseevents.WCAP8404,"ATWTAnalysisforWestinghousePWR'swith44SeriesSteamGenerators,"wasreleasedinSeptemberof1974.Followingreviewofthisreport,aswellasthemanyothervendorreportsdescribingtheanalysismodelsandresults,theNRCstaffpublished,inlate1975,itsstatusreportoneachvendoranalysisincludingdetailedguidelinesonanalysismodels,andATWSsafetyobjectives.

PII5lkIpif Sincethepublicationofthe1975statusreports,additionalinformationrelevanttoATWShasbeendevelopedbytheindustry.andtheReactorSafetyStudyGroup.Basedonreviewofthesereportsanddiscussionswithvendors,anNRCreporton"AnticipatedTransientsWithoutScramforLight-WaterReactors,"NUREG-0460,Volumes1and2,waspublishedinApril1978.SincetheissuanceofVolumes1arid2,additionalsafetyan'dcostinforma'tionandnewinsightsweredevelopedonthegeneralsubjectofquantitativeriskassessment.Basedontheseconsiderations,theNRCstaffissuedanewreport,Volume3toNUREG-0460,datedDecember1978.Volume3consideredvariousalternativeplantmodificationsforATWSrangingfromnonetothoseneededtosatisfytheproposedlicensingcriteriafornewplantsinNUREG-0460,Volumes1and2.Thestaffassessedthecorrespondingdegreesofassuranceofsafetyachievedfromthesealternativemodifications.InVolume3,thestaffalsosuggestedplantmodificationsonthebasisoftheplantdesignandage.Inordertoconfirmthestaffjudgementontheadequacyofthesedesigns,thestaffissuedrequestsforindustrytosupplythenecessarygenericanalyses.GenericWestinghouseresponses,applicabletoGinna,werepresentedtotheNRCbyreportsdatedJune8,1979,andDecember30,1979,"AnticipatedTransientsWithoutScramforWestinghousePlants."InNUREG-0460,Volume4,issuedinMarch1980forpubliccomment,theNRCstaffreviewedtheindustryresponses.Itwasconcludedthatthenecessaryverificationoftheadequacyoftheproposeddesignchangeshadnotbeenprovided.TheNRCstaffthusproposedthatearlyimprovementsinsafetyshouldbeprovided,andany l~I1ll1i'i additionalrequirementsshouldbeconsideredunderthestaffrecommendedrulemaking.TheNRChasreviewedtheindustryandtheACRScommentsinVolume4,andhaspublishedaproposedruleforresolutionofATWS.ForGinnaspecifically,itisnotanticipatedthatanymajorhardwaremodificationswillberequired.RG&EisworkingwiththeWestinghouseOwnersGrouptodevelopguidelinesfornewEmergencyOperatingInstructions(EOI's),whichwillbemodifiedintoplant-specificEmergencyProcedures.ThesewillincludeinstructionsformitigatinganATWSevent.Basedontheextensiveanalysistodateshowingnoadverseconsequences,theextremelylowprobabilityofanATWSevent,andthedevelopmentofemergencyprocedureguidelines,RG6EconsidersthattheATWSeventisbeingadequatelyaddressedfortheGinnaplant,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.

lI~

')UnresolvedSafetIssueA-11MaterialsTouhnessDescriptionofProblem:BecausethepossibilityoffailureofnuclearreactorpressurevesselsdesignedtotheASMEBoilerandPressureVesselCodeisremote,thedesignofnuclearfacilitiesdoesnotprovideprotectionItforreactorvesselfailure.However,asplantsaccumulatemoreandmoreservicetime,neutronirradiationreducesthematerialfracturetoughnessandinitialsafetymargins.RGGEStatus:r10CFR50,AppendicesGandH,requirethatcompliancewithminimumfracturetoughnessrequirementsbedemonstrated,andthatamaterialssurveillanceprogramtomonitorchangesinthefracturetoughnesspropertiesofferriticmaterialsinthereactorvesselbeltlineregionbemaintained.ThisissuewasdiscussedduringtheSystematicEvaluationProgramreviewofSEPTopicV-6,ReactorVesselIntegrity,inNUREG-0569,"EvaluationoftheIntegrityofSEPReactorVessels."Basedontherecommendationsofthatreport,RGEEcommittedtoprovideevaluationofthenextsurveillancecapsule,includingacompletechemicalanalysisofthecapsuletotheNRCforreview.Thecapsulewasremovedfromthereactorin1980,andwasshippedtoourcontractor,Westinghouse,in1981.PreliminarycharpyresultsweretransmittedtotheNRCbyletterdatedOctober6,1981.Remaininganalysesarebeingcompletednowandwillbesubmittedsoon.10

\It Resultstodateindicatevirtuallynochangeinreactorvesselmaterialpropertiesfrompreviouscapsuleresults.TheRTat30foot-poundsofenergyisapproximately125'F,wellbelowthatconsideredofconcernbyRegulatoryGuide1.99.Basedontheseacceptableresults,andtheMay3,1982letterfromDennisM.CrutchfieldtoJohnE.Maierwhichcon-sideredtheSEPTopicV-6relativetoreactorvesselintegritytobecomplete,RG6EconsidersthisUnresolvedSafetyIssuetobecompleteforGinna.11 ll~~,II' UnresolvedSafetIssueA-12FractureTouhnessofSteamGeneratorandRCSPumSuortsDescriptionofProblem:DuringthecourseofthelicensingactionforNorthAnnaPowerStationUnitsNo.1and2,anumberofquestionswereraisedastothepotentialforlamellartearingandlowfracturetoughnessofthesteamgeneratorandreactorcoolantpumpsupportmaterialsforthosefacilities.Thetoughnessofoneofthesteels(A-572)usedwasrelativelypooratanoperatingtemperatureof80'F.Sincesimilarmaterialsanddesignsareusedatotherfacilities,genericconcernswereraised.ItbecamenecessarytoreassessthefracturetoughnessofthesteamgeneratorandreactorcoolantpumpsupportmaterialsforallPWRs.TheNRCreportedatechnicalstudy(AppendixCtoNUREG-0577,"PotentialforLowFractureToughnessandLamellarTearingaPWRSteamGeneratorandReactorCoolantPumpSupports")conductedbySandiaLaboratories,whichrevealedthatnodocumentationexistsdescribinginservicefailuresresultingfromlamellartearing.RG&EStatus:Thematerialsofconstructionofthesteamgenerators'ndreactorcoolantpumps'upportshavebeendeterminedtobedifferentfromthoseusedattheNorthAnnaStation.RGEE'ssubmittalrelativetothesupportmaterialwasprovidedinareporttrans-12 I~IIKlJ"I mittedbyletterdatedJune26,1978.ItwasconcludedthatadequatefracturetoughnessexistsforthesupportsatGinnaStation.Thisreportalsoreviewedtheparameterswhichaffectthepotentialforlamellartearinginweldments-steelquality,steelfabricationpractice,weldjointdesign,gradeoffillermaterial,welddimensions,andpost-weldheattreatment.Itwasconcludedthatlamellartearingwouldnot,beaproblemfortheGinnadesignandinstallation.BasedonthereviewofthesupportsatGinna,asdescribedintheJune26,1978report,whichshowedadequatefracturetoughnessandresistanceagainstlamellartearing,plusthefactthatRG&Eiscontinuingtomonitordevelopmentsintheseareas,itisconsideredthatthisissueisbeingadequatelyaddressedfortheGinnaStation,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.13 UnresolvedSafetIssueA-17SstemsInteractioninNuclearPowerPlantsDescriptionofProblem:Duetothecomplexnatureofthedesignofnuclearpowerplants,numerousengineeringdisciplinesmustbecoordinatedandsystematicallymerged,toproduceanoperatingplant.Initialandsubsequentdesignsundergoexhaustivespecificandinterdis-ciplinaryreviewandevaluationtoensuresafetyisnotadverselyaffectedbytheinteractionofvarioussystems.InconjunctionwiththedesignreviewsconductedbytheArchitectEngineerandtheUtility,theNRCalsoperformsanindependentreviewofsysteminteractions.However,thereremainquestionsregardingboththesupportingrolethatsystemsplayandtheeffectthatonesystemcanhaveonanother.Examplesofsuchsysteminter-actionsincludepotentialfailuresasaresultofpipebreaks,fire,environmentaleffects,andseismically-inducedmotion.ThisUSIwasdividedintotwophasesbytheNRC.PhaseIwasstructuredtoidentifyareaswhereinteractionsarepossiblebetweenandamongsystemsthathavethepotentialofnegatingorseriouslydegradingtheperformanceofsafetyfunctions.Also,PhaseIwastoidentifyareaswhereNRCreviewproceduresmaynothaveproperlyaccountedfortheseinteractions.-14

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TheanticipatedPhaseIIprogramwillnotbepursuedasaUSI.PhaseII,whichwasoriginatedtotakespecificcorrectivemeasuresinareaswherethePhaseIshowsaneed,willbeperformedunderTMIActionPlanItemII.C.3,SystemsInteraction(reference:NUREG-0606,November16,1981).RG6EStatus:Thecommon-modeeffectsofvariouspostulatedexternalevents,aswellasin-planteventsandfailures,uponsafety-relatedstructures,systems,andcomponentsinordertoensuresafeshutdowncapability,havebeenextensivelystudiedfortheGinnaplant.ThesestudieshavebeenmadebothasaresultoftheSystematicEvalutionProgram(SEP)andtheTMIActionPlanitems.Areasmostrecentlystudiedincludetheeffectsofseismicevents,pipebreaks,internalandexternalflooding,windandtornadoloadings,internalmissiles,andsitehazards.Also,theRG6Efireprotectionstudy,togetherwithourproposedcourseofaction,providessubstantialassurancethatseparationandindependenceofsafety-relatedsystemsatGinnaareprovided.Basedontheextensivenatureofreviewstoensuresafeshutdowncapabilityundervariouscommon-modeevents,RG6Econ-sidersthatthisissueisbeingadequatelyaddressed,andthattheGinnaplantcanbesafelyoperatedwithoutunduerisktothehealthandsafetyofthepublic.15

~~lC UnresolvedSafetIssueA-24EnvironmentalQualificationofSafet-RelatedElectricalEuimentDescriptionofProblem:Theevolutionaryprocessofdevelopingenvironmentalqualifi-cationrequirementsandthecase-by-caseimplementationofthemhasresultedinadiversityofequipmentinstalledinnuclearplants,anddifferentlevelsofdocumentationoftheextenttowhichequipmentisenvironmentallyqualified.Inanefforttofurtherstandardizethequalificationmethodsanddocumentation,GenericTaskA-24wasdeveloped.IssuanceofNUREG-0588bytheNRCinJuly1981completedthisunresolvedsafetyissue.ForoperatingreactorssuchastheGinnaplant,the"DORGuidelines,"transmittedtoRG&EbyletterdatedFebruary15,1980,providethebasisforenvironmentalqualificationrequirements.RG6EStatus:ByletterdatedSeptember19,1980,theNRCtransmittedaRevisedOrderforModificationofLicense,effectiveimmediately,directingthatinformationregardingtheenvironmentalqualifi-cationofsafety-relatedelectricalequipmentbesubmittedbyNovember1,1980.Specifically,theNRCorderedthatthesubmittalofinformationfullyandcompletelyrespondtotheNRCStaff'srequeststransmittedbylettersdatedMarch6,1980andMarch28,1980.

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FranklinResearchCenter,undercontracttotheNRC,reviewedtheRG&Eresponses,andprovidedanassessmentviaDraftInterimTechnicalEvaluationReportFRCProjectC5257-178,datedAugust20,1980.RGaEprovidedallrequestedinformation,aswellasaresponsetotheFRCReport,byletterandreportdatedOctober31/1980.AdditionalreviewsbyFRCresultedinaJune1,1981IiSafetyEvaluationReport,withattachedFRCTERC5257-178(March18,1981).RGEE'sresponsetothisSER,datedSeptember4,1981providedforareplacementprogramforseveralsafety-relatedcomponentstoincreasethemarginsofqualificationandtoprovideadditionalqualificationdocumentationwherenecessary.AfinalcommitmentletterofJune10,1982revisedthisprogramtobeconsistentwiththeschedulestatedindraftrule10CFR50.49,Section(h).BasedonRGGE'scommitmenttomeettheregulatorycriteriaprovidedinthedraftrule,andtheacceptabilityofthepresentlyinstalledequipmenttowithstandadverseenvironmentaleffects,RGGEconsidersthatoperationoftheGinnaplantcancontinuewithoutundue'isktothehealthandsafetyofthepublic.17 UnresolvedSafetIssueA-26ReactorVesselPressureTransientProtectionDescriptionofProblem:OvertheyearstherehavebeenseveralreportedincidentsofpressuretransientsinPWRswhichhaveexceededthepressure/temperaturelimitsofthereactorvesselsinvolved.Mosteventsoccurredwhiletheplantwasinasolidwatercondition,normallyduringstartuporshutdownoperationsandatrelativelylowreactorvesseltemperatures.Thecausesoftheseoverpressurizationsweregroupedintothefollowinggeneralcategories:personnelerror,proceduraldeficiencies,componentrandomfailures,andspuriousvalveactuation.Theresultantpressuretransientwastheresultofeitheramassinput(chargingpumps,safetyinjectionpumpsandaccumulators)orathermalexpansionoftheprimaryfluid,typicallyfromheatinputfromthesteamgenerator.Inlightofthefrequencyofthesetransientsandthede-creasingreactorvesseltoughnesswithage(duetoincreasedneutronfluence)theNRCadoptedthistasktodevelopmethodstopreventandminimizetheeffectsofreactorvesseloverpressuri-zation.18 I)~I RG6EStatus:RochesterGasandElectricinstalledaReactorVesselLowTemperatureOverpressureProtectionSystemduringthe1978refuelingoutage.TheTechnicalSpecificationchanges,andtheSafetyEvaluationReportacceptingthissystem,wereissuedonApril18,1979.This"UnresolvedSafetyIssue"isconsideredcompletefortheGinnafacility.19 III~In,~1ll'K UnresolvedSafetIssue,A-31ResidualHeatRemoval'eu'irementsDescriptionofProblem:ThesafeshutdownofanuclearpowerplantfollowinganaccidentnotrelatedtoaLossofCoolantAccident(LOCA)hasbeentypicallyinterpretedasachievinga"hotstandby"condition(i.e.,thereactorisshutdown,butsystemtemperatureandpressurearestillatornearnormaloperatingvalues).Con-'iderableemphasishasbeenplacedonthehotstandbyconditionofapowerplantintheevent.ofanaccidentorotherabnormaloccurrences.Asimilaremphasishasbeenplacedonlong-termcooling,whichisachievedbytheResidualHeatRemoval(RHR)system.TheRHRsystemstartstooperatewhenthereactorcoolantpressureandtemperaturearesubstantiallylowerthantheirhotstandbyconditionvalues.However,therewasonlylimitedreviewofthetransientconditionsofgettingfromhotshutdowntocoldshutdownconditions.RG&EStatus:Safeshutdown,includingmaintenanceofhotstandby,cool-down,andcoldshutdownoperation,wastheemphasisofreviewduringtheSEPevaluationoftopicsV-10.B,V-11.B,andVII-3.ThereviewofthiscapabilityatGinnawasdocumentedintheNRC'sSafetyEvaluationReportdatedSeptember29,1981.Theonlyitemsrequiringchanges,asnotedinNUREG-0821,DraftIntegratedPlantSafetyAssessmentReport,datedMay1982are:20

~~I5 a)anevaluationoftheoperatingprocedurestodetermineifadditionalguidanceisrequiredforcontrolroompersonneltoeffectcoldshutdownusingonlysafety-relatedequipment,andvb)aTechnicalSpecificationchangetoplacetheLowTemperatureOverpressureProtectionSystem"(OPS),ineffectpriortotheuseoftheResidualHeatRemovalSystem.TheNRCnotedthatsufficientcapabilitytoeffectcoldshutdownusingonlysafety-relatedequipmentdidexistatthefacility;onlytheproceduresneededreview.Also,byprocedure,theOPSisputintoeffectpriortouseoftheRHRSystem.Further,theSandiaLaboratoriesProbabilitiesRiskAssessmentStudyforthesetwoproposedchanges(AppendixDofNUREG-0821)showedthemtobeoflowsafetysignificance.Nevertheless,RG6Ehascommittedtomakebothofthesechanges.Basedonthiscommitment,andtherelativelylowsafetypriorityofthesetwoitems,itisconsideredthat,thisUSZisbeingadequatelyaddressedfortheGinnaplant,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.21 III~15 UnresolvedSafetIssueA-36ControlofHeavLoadsNearSent,FuelDescriptionofProblem:Overheadhandlingsystems(cranes)areusedtolifthe'avyobjectsinthevicinityofspentfuelinPWRsandBWRs.Ifaheavyobject,e.g.,aspentfuelshippingcaskorshieldingblock,weretofallortipontospentfuelinthestoragepoolorthereactorcoreanddamagethefuel,therecouldbeareleaseofradioactivitytotheenvironmentandapotentialforradiationoverexposuretoinplantpersonnel.Ifmanyfuelassembliesaredamaged,andthedamagedfuelcontainedalargeamountofun-decayedfissionproducts,radiationreleasestotheenvironmentcouldexceed10CFRPart100guidelines.Additionally,aheavyobjectcouldfallonsafety-relatedequipmentandpreventitfromperformingitsintendedfunction.Ifequipmentfromredundantshutdownpathsweredamaged,safeIshutdowncapabilitymaybedefeated.RGKEStatus:TheNRCrequested,byletterdatedDecember22,1980,thatlicenseesmakeadeterminationoftheextenttowhichtheguide-linesofNUREG-0612,"ControlofHeavyLoadsatNuclearPowerPlants,"aremet.RGGErespondedtothisrequestbyletterdatedFebruary1,1982.Theauxiliarybuildingcranemovementoverthe22 SpentFuelPoolislimitedbyasystemofelectricalinterlocksexceptforasmallportionofthesoutheastcorner,andanarrowstriponthenorthside.Administrativeprocedureslimittravelinthesearasofthepool.AreviewbyFranklinResearchCenter,draftTechnicalEvaluationReportC5257-444,transmittedbyNRCletterofAugust19,1982,ispresentlybeingevaluatedbyRG&E.fInthat'eport,FRCrecommendsthatadditionaladministrativeclarificationsinloadhandlingproceduresandmoreexplicitmarkingofloadpathsbepursued.Basedonthepresentcontrolsplacedonmovementofheavy,loadsattheGinnaplant,includingin-thevicinityofspentfuel,andtheadditionalefforttobemadeinclarifyingloadpathsandprocedures,RG&EconsidersthatthisissueisbeingadequatelyaddressedfortheGinnaplant,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.23 1IIllkgJ' UnresolvedSafetIssueA-40SeismicDesinCriteriaShort-TermProramDescriptionofProblem:TheseismicdesignprocessrequiredbycurrentNRCcriteriaincludesthefollowingsequenceofevents.a.Definethemagnitudeorintensityoftheearthquakewhichwillproducethemaximumvibratorygroundmotionatthesite(thesafeshutdownearthquake)b.Determinethefree-fieldgroundmotionatthesitethatwouldresultiftheSSEoccurred.c.Determinethemotionofsitestructuresbymodifyingthefree-fieldmotiontoaccountfortheinteractionofthesitestructureswiththeunderlyingfoundationsoil.d.Determinethemotionoftheplantequipmentsupportedbythesitestructures.e.Comparetheseismicloads,inappropriatecombinationwithotherloads,onstructures,systems,andcomponentsimportanttosafety,withtheallowableloads.5lt 11J Whilethisseismicdesignsequenceincludesmanyconservativefactors,certainaspectsofthesequencemaynotbeconservativeforallplantsites.Atpresentitisbelievedthattheoverallsequenceisadequatelyconservative.Theobjectiveofthisprogramistoinvestigateselectedareasoftheseismicdesignsequencetodeterminetheirconservatismforalltypesofsites,toinvestigatealternateapproachestopartsofthedesignsequence,toquantifytheoverallconservatismofthedesignsequence,andtomodifytheNRCcriteriaintheStandardReviewPlanifchangesarefoundtobejustified.Inthismannerthisprogramwillprovideadditionalassurancethatthehealthandsafetyofthepublicisprotected,andifpossible,reducecostlydesigncon-servatismsbyimproving(1)currentseismicdesignrequirements,(2)NRC'scapabilitytoevaluatetheadequacyofseismicdesignofoperatingreactorsandplantsunderconstruction,and(3)NRC'scapabilitytoquantitativelyassesstheoveralladequacyofseismicdesignfornuclearplantsingeneral.RG&EStatus:AsapartofSystematicEvaluationProgram(SEP)TopicIII-6,SeismicDesign'onsiderations,anextensiveeffortwasmadetoevaluateanddocumenttheseismicdesignbasisofGinnaStation.ThisincludedanevaluationbytheNRCofthesitespecificresponsespectra,whichwasdocumentedinaletterfromtheNRCtoallSEPOwnersdatedJune8,1981,whichconfirmedtheconservatismoftheoriginaldesignbasis.AdditionalseismiccriteriaweredefinedbyNUREG/CR-0098,whichshowedthatthe25 1iI dampingcriteriaofRegulatoryGuide1.61weregenerallyoverlyconservative,andinNUREG/CR-1717,"Soil-StructureInteractionMethods."Further,aSeniorSeismicReviewTeamwasformedtoevaluatetheseismiccapabilityofsafety-relatedstructures,systems,andcomponents.TheresultsofthatreviewforGinnaweredocumentedinNUREG/CR-1821.RGKEhasmadecommitmentstoincreasetheseismicsafetymarginsofcertainstructures,systems,andcomponents,asdocu-mentedinthedraftIntegratedPlantSafetyAssessmentReport,NVREG-0821.Thesignificantsafetymarginavailableintheoriginalplantspecifications,togetherwiththeprogrammaticseismicupgradeofcertainsafety-relateditemsatGinna,con-firmsthatthisissueisadequatelyaddressedfortheGinnaplant,andthatplantoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.26 II UnresolvedSafetIssueA-43ContainmentEmerencSumReliabilitDescriptionof'roblem:.Followingalossofcoolantaccident(LOCA)inaPWR,waterflowingfromthebreakintheprimarysystemwouldcollectonthefloorofcontainment.Duringtheinjectionmode,waterforcorecoolingandcontainmentsprayisdrawnfromalargesupplytank.Whenthewaterreachesalowlevelinthetank,pumpsarerealignedtodrawfromthecontainment.Thisiscalledtherecirculationmodewhereinwaterisdrawnfromthecontainmentfloororsumpandpumpedtotheprimarysystemorcontainmentsprayheaders.Thisprogramaddressesthesafetyissueofadequatesumporsuppressionpoolfunctionintherecirculationmode.Itistheobjectiveofthisprogramtodevelopimprovedcriteriafordesign,testingandevaluationwhichwillprovidebetterassurancethatemergencysumpswillfunctiontosatisfysystemrequirements.Theprincipalconcernsaresomewhatinterrelatedbutarebestdiscussedseparately.Onedealswiththevariouskindsofinsulationusedonpipingandcomponentsinsidecontainment.Theconcernisthatbreak-initiateddebrisfromtheinsulationcouldcauseblockageofthesumporotherwiseadverselyaffecttheoperationofthepumps,spraynozzles,andvalvesofthesafetysystems.27 Thesecondconcerndealswiththehydraulicperformanceofthesumpasrelatedtotheoperationofsafetysystemssuppliedfromthesump.Preoperationaltestshavebeenperformedonanumberofplantstodemonstrateoperabilityintherecirculationmode.Adverseflowconditionshavebeenencounteredrequiringdesignandproceduralmodificationstoeliminatethem.Theseconditions,airentrainment,cavitation,andvortexformation,areaggravatedbyblockage.Ifnotavoided,theeffectscouldresultinlossofnetpositivesuctionhead(NPSH),andpumpdamage,inthelongtermcoolingphasefollowingaLOCA.RGGEStatus:RG6EhasbeenfollowingthesumphydraulicexperimentsbeingconductedattheAldenResearchLaboratoriesforawiderangeofsumpdesignsandadverseplanteffects.Datahaveshownthatairingestionislowerthanhadbeenexpected,andthattherehasthusbeenvirtuallynoadverseeffectonpumpperformanceunderallexceptthemostconservativelypostulatedconditions(NUREG/CR-2792).Aplant-specificanalysisoftheGinnaemergencyprocedureforswitchingfromtheRefuelingWaterStorageTanktothesump,performedaspartofSEPTopicVI-7.B,ESFSwitchover,disclosedthatRHRflowsfromthesumpwouldbequitelow,andthatsignificantNPSHmarginsareavailable.RG&EalsoparticipatedinanNRCsurveyconcerninginsulationusedinsidecontainment.ItwasnotedthattheGinnaplantdoesuseinsulationwhichcouldconceivablycausesomeblockageofthe28 lI~I)1<II sumpintakescreens.However,nospecificreviewofthemechanismtocausesuchblockagehasbeenmadefortheGinnaplant.Itwouldrequireacombinationofseverallowprobabilityoccurrences,suchasalargemajorpipebreak,lossofsignificantquantitiesofinsulationduetoresultantdynamiceffects,andmigrationofthisinsulationtothesumpscreenstocausevirtuallycompleteblockage.RGGEisawaitingthedraftproposedrevisiontotlRegulatoryGuide1.82,andtheNRC's'value-impactassessmentasaresultofplant-specificstudies,inordertodefinewhetheranyfurtheranalysisisrequiredatGinna.BasedontheextensiveNPSHmarginavailablefortheRHRpumpsat,Ginna,andthepreliminaryresultsofthesumpstudiesshowinglittleeffectonpumpperformanceduetoeffectssuchasdebrisblockageandentrainment,RGsEconsidersthatthisissueisbeingadequatelyaddressedfortheGinnaplant,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.29 Jl)'I UnresolvedSafetIssueA-44StationBlackoutDescriptionofProblem:Theissueofstation.blackoutinvolvesastudyofwhetherornotnuclearpowerplantsshouldbedesignedtoaccommodateacompletelossofallA.C.power(i.e.,alossofoff-sitesourcesandallon-siteemergencydieselsources).LossofA.C.powerforanextendedtimeinpressurizedwaterreactors,accompaniedbylossofallof'theauxiliaryfeedwaterpumps,couldresultinafailuretoadequatelycoolthereactorcore,withpotentiallyseriousconsequences.CurrentNRCguidancestatesthat,asaminimum,diversepowerdrivesshouldbeprovidedfortheredundantauxiliaryfeedwaterpumps.,ThisisnormallyaccomplishedbyutilizingoneormoreA.C.powerelectricmotordrivenpumpsandoneormoreredundantsteamturbinedrivenpumps,withthelattersystemoperationrelyingonlyonD.C.power.Oneconcernisthedesignadequacyofplantslicensedpriortoadoptionofthecurrentrequirements.RGEEStatus:TheissueofA.C.powerdependenceoftheauxiliaryfeedwatersystemwasconsideredbothasaTMIitem,andinSEPTopicX.TheGinnadesignincludesa200%steam-drivenAFWpump,aswellasfour100%motor-drivenAFWpumps.Regulatoryreviewshave30 IIlH4k7Jl hconcludedthat,basedonsystemdesignandtesting,thesteam-drivenauxiliaryfeedwater,pumpcouldprovideitssafetyfunctionwithoutrelyingonA.C.power.TheissueofonsiteandoffsitepowerreliabilitywasalsoextensivelyreviewedduringtheconductoftheSEP.ItwasconcludedduringthereviewofSEPTopicsVIII-1.A,"PotentialEquipmentFailureAssociatedWithaDegradedGridVoltage"andVIII-2,"OnsiteEmergencyPowerSystems-DieselGenerators"thattheGinnaonsiteandoffsiteA.C.powersystemshaveveryhighreliability.Also,inthereviewofSEPTopicVIII-3.A,"StationBatteryCapacityTestRequirements,"itwasconcludedthatthe8hourcapacityoftheonsitebatterieswassufficienttoensureadequateD.C.powertothestation,untilA.C.powercouldberestoredintheeventofsimultaneousfailuresofboththeon-siteandoffsiteA.C.powersystems.AnEmergencyProcedure,E-4.3,"LossofA.C.Power"hasbeendevelopedtodetailtherequiredactions.RG&EthusconcludesthattheissueofStationBlackoutisbeingadequatelyaddressedfortheGinnaStation,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.31 IIJlIIW UnresolvedSafetIssueA-45ShutdownDecaHeatRemovalReuirementsDescriptionofProblem:Undernormaloperatingconditions,powergeneratedwithinareactorisremovedassteamtoproduceelectricityviaaturbinegenerator.Followingareactorshutdown,areactorproducesinsufficientpowertooperatetheturbine;however,theradio-activedecayoffissionproductscontinuestoproduceheat(so-called"decayheat").Therefore,whenreactorshutdownoccurs,othermeasuresmustbeavailabletoremovedecayheatfromthereactor.Alllightwaterreactors(LWRs)sharetwocommondecayheatremovalfunctionalrequirements:(1)toprovideameansoftransferringdecayheatfromthereactorcoolantsystemtoanultimateheatsinkand(2)tomaintainsufficientwaterinventoryinsidethereactorvesseltoensureadequatecoolingofthereactorfuel.Thereliabilityofaparticularpowerplanttoperformthesefunctionsdependsonthefrequencyofinitiatingeventsthatrequireorjeopardizedecayheatremovaloperationsandtheprobabilitythatrequiredsystemswillrespondtoremovethedecayheat.Theprincipalmean's",forremovingthedecay>heatinaPpressurizedwaterreactor(PWR)undernormalconditionsimmediatelyfollowingreactorshutdownisthroughthestea'nlgeneratorsusing/1htheauxiliaryfeedwatersystem.FollowingtheTMI-2accident,32

~>I1~fIIHli theNRCrequiredplantstomakeimprovementstotheauxiliaryfeedwatersystems.However,theNRCstafffurtherbelievesthatprovidinganalternativemeansofdecayheatremovalcouldsub-stantiallyincreasetheplants'apabilitytodealwithabroaderspectrumoftransientsandaccidentsand,therefore,couldpotentiallysignificantlyreducetheoverallrisktothepublic.Consequently,thisUnresolvedSafetyXssuewillinvestigatealternativemeansofdecayheatremovalinPWRplants,includingbutnotlimitedtousingexistingequipmentwherepossible.Thisstudywillconsistofagenericsystemsevaluationandwillresultinrecommendationsregarding(1)theadequacyofexistingshutdowndecayheatremovalrequirements,and(2)thedesirabilityofandpossibledesignrequirementsforanalternativedecayheatremovalmethod,thatis,amethodotherthanthatnormallyassoci-atedwiththesteamgeneratorandsecondarysystem.RG&EStatus:ThedesignandqualificationoftheauxiliaryfeedwatersystemwasreviewedbothaspartoftheTMIreview,andaspartofSEPTopicsX,'AuxiliaryFeedwaterSystems,"andV-10.B,"RHRReliability."Thepresentauxiliaryfeedwatersystemconsistsoftwo100%motor-drivenauxiliaryfeedwaterpumps,a200%steam-drivenauxiliaryfeedwaterpump(independentofA.C.power),andtwo100%motor-drivenStandbyAuxiliaryFeedwaterpumps.Themotordrivenpumpsnormallytakesuctionfromon-siteCondensateStorageTanks,butcanalsogetwaterfromtheServiceWaterSystem(LakeOntario).Furthermore,amodificationmadeduring33

~~I theSEPreviewofGinnaprovidedforconnectionsallowingtheuseoftheyardfirehydrantsystem(independentofon-siteoroff-sitepower)asasourceofwaterfromthemotor-drivenandsteam-drivenpumps.AsimilarmodificationistobemadefortheStandbyAFWpumps.ItisthusapparentthatmanydiversemeansofwatersupplytoandfromtheAuxiliaryFeedwaterSystemsareavailableatGinna.DuringthecourseoftheAppendixRFireProtectionreviews,RG6Eidentifiedameansofgoingfromhotshutdowntocoldshutdownconditionscouldincludefillingofthesteamgeneratorsandsteamlinessolidwithwater,andusingthemasawater-to-waterheatexchanger.ThismethodhasbeenacceptedasviablebytheNRC.Othermeansofremovingdecayheathavealsobeeninvestigated,anddescribedintheNRC's"SafeShutdownEvaluation"fortheGinnaSEP(September29,1981report).TheseincludeuseoftheCVCS,RHR,steamgeneratorblowdownsystems,andthe"bleed-and-feed"method,usingthepressurizerPORV'sandtheSafetyInjectionpumps.GiventheextensivediversityandcapacityoftheGinnaauxiliaryfeedwatersystems,andtheothermethodsavailableforalternativedecayheatremovalmeans,RGGEconsidersthatthisissueisbeingadequatelyaddressedfortheGinnaplant,andthatoperationcancontinuewithoutunduerisktothehealthandsafetyofthepublic.34 fta3P1 UnresolvedSafetIssueA-46SeismicQualificationofEuimentin0eratinPlantsDescriptionof'Problem:IThedesigncriteriaandmethodsfortheseismicqualificationofmechanicalandelectricalequipmentinnuclearpowerplantshaveundergonesignificantchangeduringthecourseofthecommercialnuclearpowerprogram.Consequently,themarginsofsafetyprovidedinexistingequipmenttoresistseismicallyinducedloadsandperformintendedsafetyfunctionsmayvaryconsiderablyamongplantslicensedindifferenttimeframes.TheNRCstaffhasdeterminedthattheseismicqualificationoftheequipmentinoperatingplantsshouldbereassessedtoensuretheabilitytobringtheplanttoasafeshutdownconditionwhensubjecttoaseismicevent.TheNRC'sobjectiveofthisUnresolvedSafetyIssueA-46istoestablishexplicitguidelinesthatcanbeusedtojudgetheadequacyoftheseismicqualificationofmechanicalandelectricalequipmentatalloperatingplantsinlieuofattemptingtobackfitcurrentdesigncriteria.Thisguidancewillconcernequipmentrequiredtosafelyshutdowntheplant,aswellasequipmentwhosefunctionisnotrequiredforasafeshutdown,butwhosefailurecouldresultinadverseconditionswhichmightimpairshutdownfunctions.35-RGGEStatus:TheSystematicEvaluationProgram,throughtheSeniorSeismicReviewTeam,performedanauditoftheGinnasafety-relatedstructures,systems,andcomponents.ThisreportisprovidedasNUREG/CR-1821.Mostequipmentwasfoundtobecapableofwith-standingtheGinnaSSE.Incertainareassufficientdocumentationwasnotavailable.Reanalysisand,insomecases,redesignorresupportarebeingconducted.ThestatusoftheseitemsisprovidedinNUREG-0821.Inaddition,theanchorageofmajorequipmentwasaddressed.Experiencefrommajorearthquakeshasshownthatalmostallseismicallyinducedequipmentfailuresinqualityindustrialfacilitieshaveoccurredbecausethecomponentswerenotadequatelyanchoredtotheirfoundations,andthatfewequipmentfailureshaveoccurredinequipmentthatwasanchored.Asaresultofthereviewofelectricalequipmentanchorage,modificationstoupgradetheanchoragesofanumberofsafety-relatedelectricalcomponentsatGinnaweremade.RG6EisalsoparticipatinginaSeismicQualificationUtilityGroupwhichisconductingapilotprogramtoexploreanalternativemethodforseismicallyqualifyingselectednuclearplantcomponentsbasedonexperiencewiththeequipmentduringearthquakes.ThisprogramisexpectedtoassisttheNRCanditsconsultantsindevelopingqualificationmethodologyforinstalledequipmentatoperatingplants,inscreeningandassigningqualificationprior-itiesformoreefficentutilizationofNRCandindustryresources,36

)i<~

andpossiblyinqualifyingcertainclassesofequipmentonagenericbasiswithoutspecifictestingoranalysesofcomponents.Basedontheabovediscussion,RG6Econsidersthatthisissueisbeingadequatelyaddressed,andthatoperationoftheGinnaplantcancontinuewithoutunduerisktothehealthandsafetyofthepublic.37 14ll UnresolvedSafetIssueA-47SafetImlicationsofControlSstemsDescriptionofProblem:Thisissueconcernsthepotentialfortransientsoraccidentsbeingmademoresevereasaresultofthefailureormalfunctionofcontrolsystems.Thesefailuresormalfunctionsmayoccurindependently,orasaresultoftheaccidentortransientunderconsideration.Oneconcernisthepotentialforasinglefailure(suchaslossofpowersupply,shortcircuit,opencircuit,orsensorfailure)tocausesimultaneousmalfunctionofseveralcontrolsystems.Anotherconcernisforapostulatedaccidenttocausecontrolsystemfailureswhichwouldmaketheaccidentmoreseverethananalyzed.Accidentscouldconceivablycausecontrol'systemfailuresbycreatingaharshenvironmentintheareaofthecontrolequipmentorbyphysicallydamagingthecontrolequipment.Althoughitisgenerallybelievedthatsuchcontrolsystemfailureswouldnotleadtoseriouseventsorresultinconditionsthatsafetysystemscannotsafelyhandle,rigorousin-depthstudieshavenotbeenperformedtoconfirmthisbelief.RGEEStatus:TheseparationoftheReactorProtectionSystemfromnon-safetysystemswasthesubjectofSEPTopicVII-l.A.TheSERforthis38

>s Sa+SEPtopicconcludedthattheGinnaplantmetallcurrentlicensingcriteria.Additionalstudiesprobingtheinteractionofsafetyandnon-safetysystemswereperformedduringGinna'sfireprotectioni<treviewsinresponseto10CFR50AppendixR.Withi'ndesignatedfirezones,itwasassumedthatdamagetoanyequipment(oritscontrolcables,ifaffected)couldcausefailureofanytype(including"hotshorts").ThededicatedshutdownsystemproposedbyRG6Easaresultofthefireprotectionstudywillincorporatetherequiredseparationofsafetyandnon-safetysystems.InresponsetoIEInformationNotice79-22,"PotentialUnreviewedSafetyQuestiononInteractionBetweenNon-Safety-GradeSystemsandSafety-GradeSystems,"RGEEperformedanevaluationofthesepotentialeffects.ByletterdatedOctober5,1979,RG&EconcludedthatnoneofthescenariosconstitutedanunreviewedsafetyquestionfortheGinnaplant.AnotherpotentialcontrolandsafetysysteminteractionwasaddressedinRGGE'sresponsetotheNRC'sSeptember16,1980letterregardinglossofD.C.sourcesandinverters.RGEE'sinstrumentationbusandpowersupplyarrangementissuchthatlossofanyD.C.sourceorinverterwouldnotresultinthelossofanyinstrumentbuses.ThisisdescribedinourletterofOctober9,1981.39 IIt+~\~lyIII Basedontheinteractionstudiesdonetodate,theseparationalreadyprovidedbetweensafetyandnon-safetysystems,andproposedfireprotectionmodifications,RG6Econsidersthatthisissueisbeingadequatelyaddressed,andthatoperationofGinnacancontinuewithoutunduerisktothehealthand'safetyofthehlpublic.40 t~>ea,1iil.II UnresolvedSafetIssueA-48HdroenControl-MeasuresandEffectsofHdroenBurnsonSafetEuiment.DescriptionofProblem:FollowingaLOCAinanLWRplant,combustiblegases,princi-pallyhydrogen,mayaccumulateinsidetheprimaryreactorcontain-mentasaresultof:(1)metal-waterreactioninvolvingthefuelelementcladding;(2)radiolyticdecompositionofthewaterinthereactorcoreandthecontainmentsump;(3)corrosionofcertainconstructionmaterialsbythespraysolution;and(4)synergisticchemical,thermal,andradiolyticeffectsofpost-accidentenvironmentalconditionsoncontainmentprotectivecoatingsystemsandelectriccableinsulation.Intheeventofaseverelydegradedcore,alargeadditionalamountofhydrogencouldbegeneratedasaresultofthereactionbetweeenthemoltenfuelandtheconcretecontainmentbase.Othercombustiblegasesmayalsobegeneratedbythisreaction.TheaccidentatTMI-2onMarch29,1979resultedinmetal-waterreactionwhichinvolvedhydrogengenerationwellinexcessoftheamountsspecifiedinthecurrentregulations10CFRSection50.44.Asaresult,itbecameapparenttotheNRCthatadditionalhydrogencontrolandmitigationmeasuresmayneedtobeconsideredforallnuclearpowerplants.41 I>oS~IPJlA,t~l RGGEStatus:TheGinnaplanthasredundanthydrogenrecombiners,whichwouldbeusedtoprevent'he,accumulationofcombustiblemixtureofhydrogengas,in',accordance.withtheguidanceprovidedinRegulatoryGuide1.7.Also,thecontainmentpurgesystemincludesfilters,andcouldbeusedintheeventofahydrogenbuildup.AsaresultofTMImodifications,redundanthydrogenmonitorshavebeeninstalled.ThegreatamountofhydrogengeneratedatTMI-2wasduetothefailuretomaintainadequateSafetyInjectionflow.Basedonintensivetrainingofoperators,aswellasproceduralmodifications,itisnotexpectedthatthiswouldre-occur.Further,ithasbeenestimated,duringthereviewsoftheZionandSequoyahcontainments,thatareactorcontainmentbuildingcouldwithstandpressures2to3timesdesignpressureforshortperiodsoftimewithoutcatastrophicfailure,andthatalargedryreinforcedconcretecontainmentsuchasthatusedatGinnaisleastsuscept-ibletohydrogenburnconsiderationsbecauseofthelargevolumeandhighdesignpressure.BecauseofthehydrogenmonitoringandcontrolsystemsinplaceatGinna,theextensiveproceduralandtrainingupgradesasaresultoftheaccidentatTMI-2,andthepressuremarginsavailableatGinna-typecontainments,RGSEconsidersthatthehydrogenburnissueisbeingadequatelyaddressed,andthatoperationofGinnacancontinuewithoutunduerisktothehealthandsafetyofthepublic.42 awcH'es<)w'~s UnresolvedSafetIssueA-49PressurizedThermalShockDescriptionofProblem:Asaresultofoperatingexperience,itisrecognized'hattransientscanoccurinpressurizedwaterreactorscharacterizedbysevereovercoolingcausingthermalshocktothevessel,con-currentwithorfollowedbyrepressurization.Inthesepressurizedthermalshock(PTS)transients,rapidcoolingofthereactorvesselinternalsurfacecausesatemperaturedistributionacrossthereactorvesselwall.Thistemperaturedistributionresultsinthermalstr'esswithamaximumtensilestressattheinsidesurfaceofthevessel.Themagnitudeofthethermalstressdependsonthetemperaturedifferencesacrossthereactorvesselwall.Effectsofthisthermalstressarecompoundedbypressurestressesifthevesselisrepressurized.Severereactorsystemovercoolingeventswhichcouldbefollowedbyrepressurizationofthereactorvessel(PTSevents)canresultfromavarietyofcauses.Theseincludeinstru-mentationandcontrolsystemmalfunctions,andpostulatedaccidentssuchassmallbreakloss-of-coolantaccidents(LOCAs),mainsteamlinebreaks(MSLBs),feedwaterpipebreaks,orstuckopenvalvesineithertheprimaryorsecondarysystem.

0pl:I'g1fd Aslongasthefractureresistanceofthereactorvesselmaterialremainsrelativelyhigh,sucheventsarenotexpectedtocausefailure.Afterthefracturetoughnessofthevesselisreducedbyneutronirradiation(andthisoccursatafasterrateinvesselsfabricatedofmaterialswhicharerelativelysensitivetoneutronirradiationdamage),severePTSeventscouldcauseIcrackpropagation"offairly,smal.l.fl'awsthatareconservativelypostulatedtoexistneartheinnersurface.RG&EStatus:RochesterGasandElectricisanactiveparticipantintheWestinghouseOwnersGroup,whichisevaluatingthePTSquestionsforWestinghousereactors.AnalysesperformedtodateindicatethattheGinnareactorvesselcouldwithstandasevereovercoolingevent.SinceanalyseshavedemonstratedthecapabilityoftheGinnareactorvesseltowithstandsevereovercoolingtransients,andRGEEiscontinuingwiththeWestinghouseOwnersGroupandtheNRCtoreachafinalsolutiontothePTSissue,RGGEconsidersthatthisissueisbeingadequatelyaddressed,andthattheGinnaplantcancontinuetooperatewithoutunduerisktothehealthandsafetyofthepublic.44

',"I'>alsk~"1~~IV,'Ia'\l~'EplA'l,i'if11Plk1llIg~SgfQ