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)

Text

REGULATURY I'RHATIONDISTRIBUTION SYSJ'RIDS)fh-gA>>gACCESSION NBR'8210250275 OVC~DATE'2/10/19 NOTARIZED'ES DOCKETFACIL:50244RobertEmmetGinnaNuclearPlant<UnitiiRochester G05000244AUTHINANEAUTHORAFFILIATION HAIERiJ~E>>Rochester GasKElectricCorp'ECIP,NAHERECIPIENT AFFILIATION CRUTCWFIELDr DOperat)ng ReactorsBranch5

SUBJECT:

Forwardsstatusreptreunresolved safetyissuesiper NRC820617request~Infoincludesdescription ofproblembasedonNRCdocumentation.

DISTRIBUTION CODE:A001S.COPIESRECEIVED:LTR ENCLSIZE:TITLE;ORSubmittal:

GeneralDistribution NOTES:NRR/DL/SEP icy'5000244 RECIPIENT IDCODE/NAHE NRRORB5BC01INTERVAL:

ELD/WDS4NRR/DLDIRNRR/DSI/RAB RGN1COPIESLTTRENCL7710111111RECIPIENT IDCODE/NAHE NRR/DWFSDEPY08NABEGFLE04COPIESLTTRENCL11101,1EXTERNALS ACRSNRCPDRNTISNOTES:0902e1111LPDR-NSIC0305111TOTALNUHBEROFCOPIESREQUIREDTTR 25ENCL23 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,f rfc~~~'<<.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}..p i~,((cp4$T~...4I)ictrlT.I:,Ifv'IIII'I~"fT<<pa"g('cpA;,f<I z,).'"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"'/(

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~snzprriiviznIIISt<uuenzxzrzrzraw'OCHESTER GASANDELECTRICCORPORATION

~89EASTAVENUE,ROCHESTER, N.Y.14649JOHNE.MAIGRVicePresident TKLKPHONK ARKAcooK7le546-2700October19,1982DirectorofNuclearReactorRegulation Attention:

Mr.DennisM.Crutchfield, ChiefOperating ReactorsBranchNo.5U.S.NuclearRegulatory Commission Washington, D.C.20555

Subject:

Unresolved SafetyIssueStatusR.E.GinnaNuclearPowerPlantDocketNo.50-244

DearMr.Crutchfield:

ThisletterandtheattachedreportarebeingprovidedinresponsetoaletterofJune17,1982fromGusC.LainastoJohnE.Maier,requesting thestatusofapplicable Unresolved SafetyIssues(USIs)fortheR.E.GinnaNuclearPowerPlant.Inthatletter,theNRCrequested thatthefollowing information beprovidedrelativetoeachUnresolved SafetyIssue:(1)hastheissuebeenresolvedatGinna(2)ifso,howhasitbeenresolved; and(3)iffullresolution hasnotoccurred(including implementation ofnecessary

hardware, procedures, etc.),whatinterimmeasureshavebeentakentoassurethatcontinued operation wouldnotposeanunduerisktothepublic.Theattachment tothisletteraddresses eachUSIidentified inMr.Lainas'etter.

ForeachUSI,adescription oftheproblembasedonNRCdocumentation isprovidedalongwiththeRG&Estatus.I

~IV1H~,IPk(.ew~

tROCHESTER GASANDELECTICCORP.ober19,182Mr.DennisM.CrutchfieldSHEETNO.Wetrustthatourresponses totheseissuesaresufficient tobeusedintheNRCstaff'sSafetyEvaluation Reportregarding theconversion oftheProvisional Operating LicenseforGinnatoaFull-Term Operating License.Verytrulyyours,JohnE.MaierAttachment Swornandsubscribed tomeonthis19thdayofctobr1982LYNNI.HAUCKNOTARYPUBLIC,StateofII.Y.,MonrooCountyMyCommission ExpiresMarch3019.8 Unresolved SafetyIssuesStatusReportR.E.GinnaNuclearPowerPlantDocketNo.50-244October19,1982 Unresolved SafetIssueA-1WaterHammerDescription ofProblem:Waterhammeroccurswhentheinertialproperties ofapipingsystemfluidarerapidlyaltered,causingthedevelopment ofpotentially damagingpressurepulses.Since1971therehavebeennumerousincidents involving waterhammersinBWRsandPWRs.Waterhammershaveinvolvedsteamgenerator feedrings andpiping,theRHRsystem,ECCsystems,andcontainment spray,servicewater,feedwater andsteamlines.Theincidents havebeenattri-butedtosuchcausesasrapidcondensation ofsteampockets,steamdrivenslugsofwater,pumpstartupwithpartially emptylines,andrapidvalvemotion.Mostofthedamagereportedhasbeenrelatively minor,involving pipehangersandrestraints; however,therehavebeenseveralincidents whichhaveresultedinpipingandvalvedamage.Noneoftheseincidents haveinvolvedthereleaseofradioactivity totheenvirons.

RG6EStatus:Theprimaryobjective ofthistaskwastoresolvethepotential forwaterhammerdamagingthePWRsteamgenerators andfeedwater lines.AnumberoffactorsatGinnaStationreducethelikelihood ofsteamgenerator waterhammers,suchaslimitingauxiliary feedwater flowtolessthan150gpmwhensteamgenerator levelsarelowandthereisnosafetyrequirement formorefeedwater; 0~I~Ig~II automatic startofauxiliary feedwater onlossofallfeedwater, lossofoffsitepower,lowlowlevelinanyonesteamgenerator, andsafetyinjection; andthefactthatthereisonlyashortlengthoffeedwater pipingbetweenasteamgenerator anditsloopseal.Thelikelihood ofwaterhammerwasfurtherreducedbyinstallation in1979of"J"tubesontheGinnasteamgenerator feedrings.

TheNRC'sDecember20,1979SafetyEvaluation ReportforGinnarelativetosteamgenerator waterhammerconcluded thatthemeansforreducingthepotential forsteamgenerator waterhammeratthisfacility[Ginna]areadequate...andnofurtheractionisrequiredofthelicenseewithregardtosteamgenerator waterhammer."Noproblemsassociated withwaterhammerinotherfluidsystemlineshavebeenexperienced, orareanticipated, atGinna.BasedontheGinnadesign,operating experience, andoperating procedures, RG6Econsiders thatthisissueisproperlyaddressed fortheGinnaplant,andthat.operation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.2

~~IIl~'I'l 1~~Unresolve SafetIssueA-2AsmmetricBlowdownLoadsontheReactorCoolantSstemDescription ofProblem:Intheeventofapostulated LOCAatareactorvesselnozzle,asymmetric loadingonthereactorvessel,itssupports, andinternals couldresultfromtransient differential pressures inthereactorcavity.Suchloadingcouldpotentially causedamagetotheECCSlines,controlrods,otherreactorcoolantsystemcomponents, andthefuelassemblies.

RG6EStatus:RG&Eisanactiveparticipant intheWestinghouse A-2OwnersGroupaddressing thisissue.;Thefollowing Westinghouse TopicalReports,whichareapplicable toGinna,havebeensubmitted toJI1theNRC,andarecurrently beingevaluated bytheNRCstaffandtheircontractor EG6G:WCAP9558throughRev.2,5/82WCAP9787throughRev.1,5/81WCAP97496/80WCAP95706/80and10/79WCAP97486/80WCAP96622/80,1/80WCAP962811/79 t~~~y7 NUREG-0609, "Asymmetric BlowdownLoadsorPWRPrimarySystems,Resolution ofGenericTaskActionPlanA-2,"January1981,hasbeenpublished bytheNRC.Thisdocumentdefinesimplementation criteriadeveloped aspartofA-2.AlthoughnotyetissuedbytheNRC,RG&Eexpectsthatafinalacceptance oftheWestinghouse A-2OwnersGroupandRG&EanalyseswillcompleteallopenissuesrelatedtoA-2.Theanalyseshavealreadybeendiscussed withtheAdvisoryCommittee onReactorSafeguards.

Basedontheanalysesperformed aspartoftheWestinghouse A-2OwnersGroup,RG&Econsiders thattheissueofAsymmetric BlowdownLoadshasbeenadequately addressed fortheGinn'aplant,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.

IIIpI)1Js~If,'1If Unresolved SafetIssueA-3ilSteamGenerator TubeInteritDescription ofProblem:Thisissueaddresses thecapability ofsteamgenerator tubestomaintaintheirintegrity duringnormaloperation andunderaccidentconditions,,

withadequatesafety.margins.PWRsteamfIgenerator tubinginsomeplantshasexperienced tubewallthinning(wastage),

intergranul'aZ attack,stress-corrosion

cracking, anddenting.RG&EStatus:Rochester GasandElectricreplacedtheoriginalphosphate secondary sidewaterchemistry treatment withanall-volatile treatment inNovember1974andaddedfullflowcondensate polishing demineralizers in1978.Atpresent,lessthan5%ofthetubesineachsteamgenerator havebeenplugged.Inaddition, 21tubesintheBsteamgenerator havebeensleeved.Theprimaryreasonsfortuberepairhavebeenwastageandcreviceintergranular attack.Asaresultofthechangeinchemistry, wastagenolongerappearstobeoccurring.

RGEE'spresentprogramofsteamgenerator tubeinspections providesforeddycurrenttestsofthetubes,tubesheetwaterlancing,andcrevicecleaningifdetermined tobenecessary.

Further,RG&Ehasproposedasleevingprogramtoinstallsleeves asapreventive measureonthosesteamgenerator tubesconsidered mostsusceptible tocreviceintergranular attack.OnJanuary25,1982,GinnaStationexperienced asteamgenerator tuberupture.Thedescription oftheevent,andtherestartSafetyEvaluation Report,areNUREG-0909 andNUREG-0916, respectively.

Basedontheinservice inspection andtestingbeingper-formedontheGinnasteamgenerators, theexistence ofthemetalimpactmonitoring systeminstalled onthesteamgenerators, andtheproposedpreventive sleevingprogram,RG6Econsiders thatthesubjectofSteamGenerator TubeIntegrity isbeingadequately addressed fortheGinnaplant,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.

Unresolved SafetIssueA-9AnticiatedTransients WithoutScram(ATWS)Description ofProblem:Duringoperation ofanuclearpowerplant,keyparameters aremonitored andusedtoactuatesafetysystemsthatinitiateshutdown(SCRAM)ofthereactor.Foranumberofyearstherehasbeenconcernthat,following atemporarily abnormaloperation condition,.

or!anticipated transient,".

afailurecouldoccurinfJt1'YV',1thesystemsrequire'd'o insert,thecontrolrodsintothereactor,Jandaresultant scrammightnotoccur.Failuretoscramduringorfollowing ananticipated transient,'would increasetheseverityofthetransient, andcouldcausefueldamage.RGGEStatus:TheTechnical ReportonAnticipated Transients WithoutScramforWater-Cooled PowerReactors, WASH-1270, discussed theprob-abilityofanATWSeventandanappropriate safetyobjective fortheseevents.WCAP8404,"ATWTAnalysisforWestinghouse PWR'swith44SeriesSteamGenerators,"

wasreleasedinSeptember of1974.Following reviewofthisreport,aswellasthemanyothervendorreportsdescribing theanalysismodelsandresults,theNRCstaffpublished, inlate1975,itsstatusreportoneachvendoranalysisincluding detailedguidelines onanalysismodels,andATWSsafetyobjectives.

PII5lkIpif Sincethepublication ofthe1975statusreports,additional information relevanttoATWShasbeendeveloped bytheindustry.

andtheReactorSafetyStudyGroup.Basedonreviewofthesereportsanddiscussions withvendors,anNRCreporton"Anticipated Transients WithoutScramforLight-Water Reactors,"

NUREG-0460, Volumes1and2,waspublished inApril1978.SincetheissuanceofVolumes1arid2,additional safetyan'dcostinforma'tion andnewinsightsweredeveloped onthegeneralsubjectofquantitative riskassessment.

Basedontheseconsiderations, theNRCstaffissuedanewreport,Volume3toNUREG-0460, datedDecember1978.Volume3considered variousalternative plantmodifications forATWSrangingfromnonetothoseneededtosatisfytheproposedlicensing criteriafornewplantsinNUREG-0460, Volumes1and2.Thestaffassessedthecorresponding degreesofassurance ofsafetyachievedfromthesealternative modifications.

InVolume3,thestaffalsosuggested plantmodifications onthebasisoftheplantdesignandage.Inordertoconfirmthestaffjudgement ontheadequacyofthesedesigns,thestaffissuedrequestsforindustrytosupplythenecessary genericanalyses.

GenericWestinghouse responses, applicable toGinna,werepresented totheNRCbyreportsdatedJune8,1979,andDecember30,1979,"Anticipated Transients WithoutScramforWestinghouse Plants."InNUREG-0460, Volume4,issuedinMarch1980forpubliccomment,theNRCstaffreviewedtheindustryresponses.

Itwasconcluded thatthenecessary verification oftheadequacyoftheproposeddesignchangeshadnotbeenprovided.

TheNRCstaffthusproposedthatearlyimprovements insafetyshouldbeprovided, andany l~I1ll1i'i additional requirements shouldbeconsidered underthestaffrecommended rulemaking.

TheNRChasreviewedtheindustryandtheACRScommentsinVolume4,andhaspublished aproposedruleforresolution ofATWS.ForGinnaspecifically, itisnotanticipated thatanymajorhardwaremodifications willberequired.

RG&EisworkingwiththeWestinghouse OwnersGrouptodevelopguidelines fornewEmergency Operating Instructions (EOI's),whichwillbemodifiedintoplant-specific Emergency Procedures.

Thesewillincludeinstructions formitigating anATWSevent.Basedontheextensive analysistodateshowingnoadverseconsequences, theextremely lowprobability ofanATWSevent,andthedevelopment ofemergency procedure guidelines, RG6Econsiders thattheATWSeventisbeingadequately addressed fortheGinnaplant,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.

lI~

')Unresolved SafetIssueA-11Materials TouhnessDescription ofProblem:Becausethepossibility offailureofnuclearreactorpressurevesselsdesignedtotheASMEBoilerandPressureVesselCodeisremote,thedesignofnuclearfacilities doesnotprovideprotection Itforreactorvesselfailure.However,asplantsaccumulate moreandmoreservicetime,neutronirradiation reducesthematerialfracturetoughness andinitialsafetymargins.RGGEStatus:r10CFR50,Appendices GandH,requirethatcompliance withminimumfracturetoughness requirements bedemonstrated, andthatamaterials surveillance programtomonitorchangesinthefracturetoughness properties offerriticmaterials inthereactorvesselbeltlineregionbemaintained.

Thisissuewasdiscussed duringtheSystematic Evaluation ProgramreviewofSEPTopicV-6,ReactorVesselIntegrity, inNUREG-0569, "Evaluation oftheIntegrity ofSEPReactorVessels."

Basedontherecommendations ofthatreport,RGEEcommitted toprovideevaluation ofthenextsurveillance capsule,including acompletechemicalanalysisofthecapsuletotheNRCforreview.Thecapsulewasremovedfromthereactorin1980,andwasshippedtoourcontractor, Westinghouse, in1981.Preliminary charpyresultsweretransmitted totheNRCbyletterdatedOctober6,1981.Remaining analysesarebeingcompleted nowandwillbesubmitted soon.10

\It Resultstodateindicatevirtually nochangeinreactorvesselmaterialproperties frompreviouscapsuleresults.TheRTat30foot-pounds ofenergyisapproximately 125'F,wellbelowthatconsidered ofconcernbyRegulatory Guide1.99.Basedontheseacceptable results,andtheMay3,1982letterfromDennisM.Crutchfield toJohnE.Maierwhichcon-sideredtheSEPTopicV-6relativetoreactorvesselintegrity tobecomplete, RG6Econsiders thisUnresolved SafetyIssuetobecompleteforGinna.11 ll~~,II' Unresolved SafetIssueA-12FractureTouhnessofSteamGenerator andRCSPumSuortsDescription ofProblem:Duringthecourseofthelicensing actionforNorthAnnaPowerStationUnitsNo.1and2,anumberofquestions wereraisedastothepotential forlamellartearingandlowfracturetoughness ofthesteamgenerator andreactorcoolantpumpsupportmaterials forthosefacilities.

Thetoughness ofoneofthesteels(A-572)usedwasrelatively pooratanoperating temperature of80'F.Sincesimilarmaterials anddesignsareusedatotherfacilities, genericconcernswereraised.Itbecamenecessary toreassessthefracturetoughness ofthesteamgenerator andreactorcoolantpumpsupportmaterials forallPWRs.TheNRCreportedatechnical study(Appendix CtoNUREG-0577, "Potential forLowFractureToughness andLamellarTearingaPWRSteamGenerator andReactorCoolantPumpSupports"

)conducted bySandiaLaboratories, whichrevealedthatnodocumentation existsdescribing inservice failuresresulting fromlamellartearing.RG&EStatus:Thematerials ofconstruction ofthesteamgenerators'nd reactorcoolantpumps'upports havebeendetermined tobedifferent fromthoseusedattheNorthAnnaStation.RGEE'ssubmittal relativetothesupportmaterialwasprovidedinareporttrans-12 I~IIKlJ"I mittedbyletterdatedJune26,1978.Itwasconcluded thatadequatefracturetoughness existsforthesupportsatGinnaStation.Thisreportalsoreviewedtheparameters whichaffectthepotential forlamellartearinginweldments

-steelquality,steelfabrication

practice, weldjointdesign,gradeoffillermaterial, welddimensions, andpost-weld heattreatment.

Itwasconcluded thatlamellartearingwouldnot,beaproblemfortheGinnadesignandinstallation.

BasedonthereviewofthesupportsatGinna,asdescribed intheJune26,1978report,whichshowedadequatefracturetoughness andresistance againstlamellartearing,plusthefactthatRG&Eiscontinuing tomonitordevelopments intheseareas,itisconsidered thatthisissueisbeingadequately addressed fortheGinnaStation,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.13 Unresolved SafetIssueA-17SstemsInteraction inNuclearPowerPlantsDescription ofProblem:Duetothecomplexnatureofthedesignofnuclearpowerplants,numerousengineering disciplines mustbecoordinated andsystematically merged,to produceanoperating plant.Initialandsubsequent designsundergoexhaustive specificandinterdis-ciplinary reviewandevaluation toensuresafetyisnotadversely affectedbytheinteraction ofvarioussystems.Inconjunction withthedesignreviewsconducted bytheArchitect EngineerandtheUtility,theNRCalsoperformsanindependent reviewofsysteminteractions.

However,thereremainquestions regarding boththesupporting rolethatsystemsplayandtheeffectthatonesystemcanhaveonanother.Examplesofsuchsysteminter-actionsincludepotential failuresasaresultofpipebreaks,fire,environmental effects,andseismically-induced motion.ThisUSIwasdividedintotwophasesbytheNRC.PhaseIwasstructured toidentifyareaswhereinteractions arepossiblebetweenandamongsystemsthathavethepotential ofnegatingorseriously degrading theperformance ofsafetyfunctions.

Also,PhaseIwastoidentifyareaswhereNRCreviewprocedures maynothaveproperlyaccounted fortheseinteractions.

-14

~~

Theanticipated PhaseIIprogramwillnotbepursuedasaUSI.PhaseII,whichwasoriginated totakespecificcorrective measuresinareaswherethePhaseIshowsaneed,willbeperformed underTMIActionPlanItemII.C.3,SystemsInteraction (reference:

NUREG-0606, November16,1981).RG6EStatus:Thecommon-mode effectsofvariouspostulated externalevents,aswellasin-planteventsandfailures, uponsafety-relatedstructures, systems,andcomponents inordertoensuresafeshutdowncapability, havebeenextensively studiedfortheGinnaplant.ThesestudieshavebeenmadebothasaresultoftheSystematic Evalution Program(SEP)andtheTMIActionPlanitems.Areasmostrecentlystudiedincludetheeffectsofseismicevents,pipebreaks,internalandexternalflooding, windandtornadoloadings, internalmissiles, andsitehazards.Also,theRG6Efireprotection study,togetherwithourproposedcourseofaction,providessubstantial assurance thatseparation andindependence ofsafety-related systemsatGinnaareprovided.

Basedontheextensive natureofreviewstoensuresafeshutdowncapability undervariouscommon-mode events,RG6Econ-sidersthatthisissueisbeingadequately addressed, andthattheGinnaplantcanbesafelyoperatedwithoutunduerisktothehealthandsafetyofthepublic.15

~~lC Unresolved SafetIssueA-24Environmental Qualification ofSafet-RelatedElectrical EuimentDescription ofProblem:Theevolutionary processofdeveloping environmental qualifi-cationrequirements andthecase-by-case implementation ofthemhasresultedinadiversity ofequipment installed innuclearplants,anddifferent levelsofdocumentation oftheextenttowhichequipment isenvironmentally qualified.

Inanefforttofurtherstandardize thequalification methodsanddocumentation, GenericTaskA-24wasdeveloped.

IssuanceofNUREG-0588 bytheNRCinJuly1981completed thisunresolved safetyissue.Foroperating reactorssuchastheGinnaplant,the"DORGuidelines,"

transmitted toRG&EbyletterdatedFebruary15,1980,providethebasisforenvironmental qualification requirements.

RG6EStatus:ByletterdatedSeptember 19,1980,theNRCtransmitted aRevisedOrderforModification ofLicense,effective immediately, directing thatinformation regarding theenvironmental qualifi-cationofsafety-related electrical equipment besubmitted byNovember1,1980.Specifically, theNRCorderedthatthesubmittal ofinformation fullyandcompletely respondtotheNRCStaff'srequeststransmitted bylettersdatedMarch6,1980andMarch28,1980.

I~~V\

FranklinResearchCenter,undercontracttotheNRC,reviewedtheRG&Eresponses, andprovidedanassessment viaDraftInterimTechnical Evaluation ReportFRCProjectC5257-178, datedAugust20,1980.RGaEprovidedallrequested information, aswellasaresponsetotheFRCReport,byletterandreportdatedOctober31/1980.Additional reviewsbyFRCresultedinaJune1,1981IiSafetyEvaluation Report,withattachedFRCTERC5257-178 (March18,1981).RGEE'sresponsetothisSER,datedSeptember 4,1981providedforareplacement programforseveralsafety-related components toincreasethemarginsofqualification andtoprovideadditional qualification documentation wherenecessary.

Afinalcommitment letterofJune10,1982revisedthisprogramtobeconsistent withtheschedulestatedindraftrule10CFR50.49,Section(h).BasedonRGGE'scommitment tomeettheregulatory criteriaprovidedinthedraftrule,andtheacceptability ofthepresently installed equipment towithstand adverseenvironmental effects,RGGEconsiders thatoperation oftheGinnaplantcancontinuewithoutundue'isk tothehealthandsafetyofthepublic.17 Unresolved SafetIssueA-26ReactorVesselPressureTransient Protection Description ofProblem:Overtheyearstherehavebeenseveralreportedincidents ofpressuretransients inPWRswhichhaveexceededthepressure/

temperature limitsofthereactorvesselsinvolved.

Mosteventsoccurredwhiletheplantwasinasolidwatercondition, normallyduringstartuporshutdownoperations andatrelatively lowreactorvesseltemperatures.

Thecausesoftheseoverpressurizations weregroupedintothefollowing generalcategories:

personnel error,procedural deficiencies, component randomfailures, andspuriousvalveactuation.

Theresultant pressuretransient wastheresultofeitheramassinput(charging pumps,safetyinjection pumpsandaccumulators) orathermalexpansion oftheprimaryfluid,typically fromheatinputfromthesteamgenerator.

Inlightofthefrequency ofthesetransients andthede-creasingreactorvesseltoughness withage(duetoincreased neutronfluence)theNRCadoptedthistasktodevelopmethodstopreventandminimizetheeffectsofreactorvesseloverpressuri-zation.18 I)~I RG6EStatus:Rochester GasandElectricinstalled aReactorVesselLowTemperature Overpressure Protection Systemduringthe1978refueling outage.TheTechnical Specification changes,andtheSafetyEvaluation Reportaccepting thissystem,wereissuedonApril18,1979.This"Unresolved SafetyIssue"isconsidered completefortheGinnafacility.

19 III~In,~1ll'K Unresolved SafetIssue,A-31 ResidualHeatRemoval'e u'irements Description ofProblem:Thesafeshutdownofanuclearpowerplantfollowing anaccidentnotrelatedtoaLossofCoolantAccident(LOCA)hasbeentypically interpreted asachieving a"hotstandby"condition (i.e.,thereactorisshutdown,butsystemtemperature andpressurearestillatornearnormaloperating values).Con-'iderable emphasishasbeenplacedonthehotstandbycondition ofapowerplantintheevent.ofanaccidentorotherabnormaloccurrences.

Asimilaremphasishasbeenplacedonlong-term cooling,whichisachievedbytheResidualHeatRemoval(RHR)system.TheRHRsystemstartstooperatewhenthereactorcoolantpressureandtemperature aresubstantially lowerthantheirhotstandbycondition values.However,therewasonlylimitedreviewofthetransient conditions ofgettingfromhotshutdowntocoldshutdownconditions.

RG&EStatus:Safeshutdown, including maintenance ofhotstandby,cool-down,andcoldshutdownoperation, wastheemphasisofreviewduringtheSEPevaluation oftopicsV-10.B,V-11.B,andVII-3.Thereviewofthiscapability atGinnawasdocumented intheNRC'sSafetyEvaluation ReportdatedSeptember 29,1981.Theonlyitemsrequiring changes,asnotedinNUREG-0821, DraftIntegrated PlantSafetyAssessment Report,datedMay1982are:20

~~I5 a)anevaluation oftheoperating procedures todetermine ifadditional guidanceisrequiredforcontrolroompersonnel toeffectcoldshutdownusingonlysafety-related equipment, andvb)aTechnical Specification changetoplacetheLowTemperature Overpressure Protection System"(OPS),ineffectpriortotheuseoftheResidualHeatRemovalSystem.TheNRCnotedthatsufficient capability toeffectcoldshutdownusingonlysafety-related equipment didexistatthefacility; onlytheprocedures neededreview.Also,byprocedure, theOPSisputintoeffectpriortouseoftheRHRSystem.Further,theSandiaLaboratories Probabilities RiskAssessment Studyforthesetwoproposedchanges(Appendix DofNUREG-0821) showedthemtobeoflowsafetysignificance.

Nevertheless, RG6Ehascommitted tomakebothofthesechanges.Basedonthiscommitment, andtherelatively lowsafetypriorityofthesetwoitems,itisconsidered that,thisUSZisbeingadequately addressed fortheGinnaplant,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.21 III~15 Unresolved SafetIssueA-36ControlofHeavLoadsNearSent,FuelDescription ofProblem:Overheadhandlingsystems(cranes)areusedtolifthe'avyobjectsinthevicinityofspentfuelinPWRsandBWRs.Ifaheavyobject,e.g.,aspentfuelshippingcaskorshielding block,weretofallortipontospentfuelinthestoragepoolorthereactorcoreanddamagethefuel,therecouldbeareleaseofradioactivity totheenvironment andapotential forradiation overexposure toinplantpersonnel.

Ifmanyfuelassemblies aredamaged,andthedamagedfuelcontained alargeamountofun-decayedfissionproducts, radiation releasestotheenvironment couldexceed10CFRPart100guidelines.

Additionally, aheavyobjectcouldfallonsafety-related equipment andpreventitfromperforming itsintendedfunction.

Ifequipment fromredundant shutdownpathsweredamaged,safeIshutdowncapability maybedefeated.

RGKEStatus:TheNRCrequested, byletterdatedDecember22,1980,thatlicensees makeadetermination oftheextenttowhichtheguide-linesofNUREG-0612, "ControlofHeavyLoadsatNuclearPowerPlants,"aremet.RGGEresponded tothisrequestbyletterdatedFebruary1,1982.Theauxiliary buildingcranemovementoverthe22 SpentFuelPoolislimitedbyasystemofelectrical interlocks exceptforasmallportionofthesoutheast corner,andanarrowstriponthenorthside.Administrative procedures limittravelinthesearasofthepool.AreviewbyFranklinResearchCenter,draftTechnical Evaluation ReportC5257-444, transmitted byNRCletterofAugust19,1982,ispresently beingevaluated byRG&E.fInthat'eport, FRCrecommends thatadditional administrative clarifications inloadhandlingprocedures andmoreexplicitmarkingofloadpathsbepursued.Basedonthepresentcontrolsplacedonmovementofheavy,loadsattheGinnaplant,including in-thevicinityofspentfuel,andtheadditional efforttobemadeinclarifying loadpathsandprocedures, RG&Econsiders thatthisissueisbeingadequately addressed fortheGinnaplant,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.23 1IIllkgJ' Unresolved SafetIssueA-40SeismicDesinCriteriaShort-Term ProramDescription ofProblem:TheseismicdesignprocessrequiredbycurrentNRCcriteriaincludesthefollowing sequenceofevents.a.Definethemagnitude orintensity oftheearthquake whichwillproducethemaximumvibratory groundmotionatthesite(thesafeshutdownearthquake) b.Determine thefree-field groundmotionatthesitethatwouldresultiftheSSEoccurred.

c.Determine themotionofsitestructures bymodifying thefree-field motiontoaccountfortheinteraction ofthesitestructures withtheunderlying foundation soil.d.Determine themotionoftheplantequipment supported bythesitestructures.

e.Comparetheseismicloads,inappropriate combination withotherloads,onstructures, systems,andcomponents important tosafety,withtheallowable loads.5lt 11J Whilethisseismicdesignsequenceincludesmanyconservative factors,certainaspectsofthesequencemaynotbeconservative forallplantsites.Atpresentitisbelievedthattheoverallsequenceisadequately conservative.

Theobjective ofthisprogramistoinvestigate selectedareasoftheseismicdesignsequencetodetermine theirconservatism foralltypesofsites,toinvestigate alternate approaches topartsofthedesignsequence, toquantifytheoverallconservatism ofthedesignsequence, andtomodifytheNRCcriteriaintheStandardReviewPlanifchangesarefoundtobejustified.

Inthismannerthisprogramwillprovideadditional assurance thatthehealthandsafetyofthepublicisprotected, andifpossible, reducecostlydesigncon-servatisms byimproving (1)currentseismicdesignrequirements, (2)NRC'scapability toevaluatetheadequacyofseismicdesignofoperating reactorsandplantsunderconstruction, and(3)NRC'scapability toquantitatively assesstheoveralladequacyofseismicdesignfornuclearplantsingeneral.RG&EStatus:AsapartofSystematic Evaluation Program(SEP)TopicIII-6,SeismicDesign'onsiderations, anextensive effortwasmadetoevaluateanddocumenttheseismicdesignbasisofGinnaStation.Thisincludedanevaluation bytheNRCofthesitespecificresponsespectra,whichwasdocumented inaletterfromtheNRCtoallSEPOwnersdatedJune8,1981,whichconfirmed theconservatism oftheoriginaldesignbasis.Additional seismiccriteriaweredefinedbyNUREG/CR-0098, whichshowedthatthe25 1iI dampingcriteriaofRegulatory Guide1.61weregenerally overlyconservative, andinNUREG/CR-1717, "Soil-Structure Interaction Methods."

Further,aSeniorSeismicReviewTeamwasformedtoevaluatetheseismiccapability ofsafety-related structures, systems,andcomponents.

TheresultsofthatreviewforGinnaweredocumented inNUREG/CR-1821.

RGKEhasmadecommitments toincreasetheseismicsafetymarginsofcertainstructures, systems,andcomponents, asdocu-mentedinthedraftIntegrated PlantSafetyAssessment Report,NVREG-0821.

Thesignificant safetymarginavailable intheoriginalplantspecifications, togetherwiththeprogrammatic seismicupgradeofcertainsafety-related itemsatGinna,con-firmsthatthisissueisadequately addressed fortheGinnaplant,andthatplantoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.26 II Unresolved SafetIssueA-43Containment EmerencSumReliabilit Description of'roblem:.

Following alossofcoolantaccident(LOCA)inaPWR,waterflowingfromthebreakintheprimarysystemwouldcollectonthefloorofcontainment.

Duringtheinjection mode,waterforcorecoolingandcontainment sprayisdrawnfromalargesupplytank.Whenthewaterreachesalowlevelinthetank,pumpsarerealigned todrawfromthecontainment.

Thisiscalledtherecirculation modewhereinwaterisdrawnfromthecontainment floororsumpandpumpedtotheprimarysystemorcontainment sprayheaders.Thisprogramaddresses thesafetyissueofadequatesumporsuppression poolfunctionintherecirculation mode.Itistheobjective ofthisprogramtodevelopimprovedcriteriafordesign,testingandevaluation whichwillprovidebetterassurance thatemergency sumpswillfunctiontosatisfysystemrequirements.

Theprincipal concernsaresomewhatinterrelated butarebestdiscussed separately.

Onedealswiththevariouskindsofinsulation usedonpipingandcomponents insidecontainment.

Theconcernisthatbreak-initiated debrisfromtheinsulation couldcauseblockageofthesumporotherwise adversely affecttheoperation ofthepumps,spraynozzles,andvalvesofthesafetysystems.27 Thesecondconcerndealswiththehydraulic performance ofthesumpasrelatedtotheoperation ofsafetysystemssuppliedfromthesump.Preoperational testshavebeenperformed onanumberofplantstodemonstrate operability intherecirculation mode.Adverseflowconditions havebeenencountered requiring designandprocedural modifications toeliminate them.Theseconditions, airentrainment, cavitation, andvortexformation, areaggravated byblockage.

Ifnotavoided,theeffectscouldresultinlossofnetpositivesuctionhead(NPSH),andpumpdamage,inthelongtermcoolingphasefollowing aLOCA.RGGEStatus:RG6Ehasbeenfollowing thesumphydraulic experiments beingconducted attheAldenResearchLaboratories forawiderangeofsumpdesignsandadverseplanteffects.Datahaveshownthatairingestion islowerthanhadbeenexpected, andthattherehasthusbeenvirtually noadverseeffectonpumpperformance underallexceptthemostconservatively postulated conditions (NUREG/CR-2792).

Aplant-specific analysisoftheGinnaemergency procedure forswitching fromtheRefueling WaterStorageTanktothesump,performed aspartofSEPTopicVI-7.B,ESFSwitchover, disclosed thatRHRflowsfromthesumpwouldbequitelow,andthatsignificant NPSHmarginsareavailable.

RG&Ealsoparticipated inanNRCsurveyconcerning insulation usedinsidecontainment.

ItwasnotedthattheGinnaplantdoesuseinsulation whichcouldconceivably causesomeblockageofthe28 lI~I)1<II sumpintakescreens.However,nospecificreviewofthemechanism tocausesuchblockagehasbeenmadefortheGinnaplant.Itwouldrequireacombination ofseverallowprobability occurrences, suchasalargemajorpipebreak,lossofsignificant quantities ofinsulation duetoresultant dynamiceffects,andmigration ofthisinsulation tothesumpscreenstocausevirtually completeblockage.

RGGEisawaitingthedraftproposedrevisiontotlRegulatory Guide1.82,andtheNRC's'value-impact assessment asaresultofplant-specific studies,inordertodefinewhetheranyfurtheranalysisisrequiredatGinna.Basedontheextensive NPSHmarginavailable fortheRHRpumpsat,Ginna,andthepreliminary resultsofthesumpstudiesshowinglittleeffectonpumpperformance duetoeffectssuchasdebrisblockageandentrainment, RGsEconsiders thatthisissueisbeingadequately addressed fortheGinnaplant,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.29 Jl)'I Unresolved SafetIssueA-44StationBlackoutDescription ofProblem:Theissueofstation.blackoutinvolvesastudyofwhetherornotnuclearpowerplantsshouldbedesignedtoaccommodate acompletelossofallA.C.power(i.e.,alossofoff-sitesourcesandallon-siteemergency dieselsources).

LossofA.C.powerforanextendedtimeinpressurized waterreactors, accompanied bylossofallof'theauxiliary feedwater pumps,couldresultinafailuretoadequately coolthereactorcore,withpotentially seriousconsequences.

CurrentNRCguidancestatesthat,asaminimum,diversepowerdrivesshouldbeprovidedfortheredundant auxiliary feedwater pumps.,Thisisnormallyaccomplished byutilizing oneormoreA.C.powerelectricmotordrivenpumpsandoneormoreredundant steamturbinedrivenpumps,withthelattersystemoperation relyingonlyonD.C.power.Oneconcernisthedesignadequacyofplantslicensedpriortoadoptionofthecurrentrequirements.

RGEEStatus:TheissueofA.C.powerdependence oftheauxiliary feedwater systemwasconsidered bothasaTMIitem,andinSEPTopicX.TheGinnadesignincludesa200%steam-driven AFWpump,aswellasfour100%motor-driven AFWpumps.Regulatory reviewshave30 IIlH4k7Jl hconcluded that,basedonsystemdesignandtesting,thesteam-drivenauxiliary feedwater, pumpcouldprovideitssafetyfunctionwithoutrelyingonA.C.power.Theissueofonsiteandoffsitepowerreliability wasalsoextensively reviewedduringtheconductoftheSEP.Itwasconcluded duringthereviewofSEPTopicsVIII-1.A, "Potential Equipment FailureAssociated WithaDegradedGridVoltage"andVIII-2,"OnsiteEmergency PowerSystems-DieselGenerators" thattheGinnaonsiteandoffsiteA.C.powersystemshaveveryhighreliability.

Also,inthereviewofSEPTopicVIII-3.A, "StationBatteryCapacityTestRequirements,"

itwasconcluded thatthe8hourcapacityoftheonsitebatteries wassufficient toensureadequateD.C.powertothestation,untilA.C.powercouldberestoredintheeventofsimultaneous failuresofboththeon-siteandoffsiteA.C.powersystems.AnEmergency Procedure, E-4.3,"LossofA.C.Power"hasbeendeveloped todetailtherequiredactions.RG&Ethusconcludes thattheissueofStationBlackoutisbeingadequately addressed fortheGinnaStation,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.31 IIJlIIW Unresolved SafetIssueA-45ShutdownDecaHeatRemovalReuirements Description ofProblem:Undernormaloperating conditions, powergenerated withinareactorisremovedassteamtoproduceelectricity viaaturbinegenerator.

Following areactorshutdown, areactorproducesinsufficient powertooperatetheturbine;however,theradio-activedecayoffissionproductscontinues toproduceheat(so-called"decayheat").Therefore, whenreactorshutdownoccurs,othermeasuresmustbeavailable toremovedecayheatfromthereactor.Alllightwaterreactors(LWRs)sharetwocommondecayheatremovalfunctional requirements:

(1)toprovideameansoftransferring decayheatfromthereactorcoolantsystemtoanultimateheatsinkand(2)tomaintainsufficient waterinventory insidethereactorvesseltoensureadequatecoolingofthereactorfuel.Thereliability ofaparticular powerplanttoperformthesefunctions dependsonthefrequency ofinitiating eventsthatrequireorjeopardize decayheatremovaloperations andtheprobability thatrequiredsystemswillrespondtoremovethedecayheat.Theprincipal mean's",forremovingthedecay>heatinaPpressurized waterreactor(PWR)undernormalconditions immediately following reactorshutdownisthroughthestea'nlgenerators using/1htheauxiliary feedwater system.Following theTMI-2accident, 32

~>I1~fIIHli theNRCrequiredplantstomakeimprovements totheauxiliary feedwater systems.However,theNRCstafffurtherbelievesthatproviding analternative meansofdecayheatremovalcouldsub-stantially increasetheplants'apability todealwithabroaderspectrumoftransients andaccidents and,therefore, couldpotentially significantly reducetheoverallrisktothepublic.Consequently, thisUnresolved SafetyXssuewillinvestigate alternative meansofdecayheatremovalinPWRplants,including butnotlimitedtousingexistingequipment wherepossible.

Thisstudywillconsistofagenericsystemsevaluation andwillresultinrecommendations regarding (1)theadequacyofexistingshutdowndecayheatremovalrequirements, and(2)thedesirability ofandpossibledesignrequirements foranalternative decayheatremovalmethod,thatis,amethodotherthanthatnormallyassoci-atedwiththesteamgenerator andsecondary system.RG&EStatus:Thedesignandqualification oftheauxiliary feedwater systemwasreviewedbothaspartoftheTMIreview,andaspartofSEPTopicsX,'Auxiliary Feedwater Systems,"

andV-10.B,"RHRReliability."

Thepresentauxiliary feedwater systemconsistsoftwo100%motor-driven auxiliary feedwater pumps,a200%steam-drivenauxiliary feedwater pump(independent ofA.C.power),andtwo100%motor-driven StandbyAuxiliary Feedwater pumps.Themotordrivenpumpsnormallytakesuctionfromon-siteCondensate StorageTanks,butcanalsogetwaterfromtheServiceWaterSystem(LakeOntario).

Furthermore, amodification madeduring33

~~I theSEPreviewofGinnaprovidedforconnections allowingtheuseoftheyardfirehydrantsystem(independent ofon-siteoroff-sitepower)asasourceofwaterfromthemotor-driven andsteam-drivenpumps.Asimilarmodification istobemadefortheStandbyAFWpumps.ItisthusapparentthatmanydiversemeansofwatersupplytoandfromtheAuxiliary Feedwater Systemsareavailable atGinna.DuringthecourseoftheAppendixRFireProtection reviews,RG6Eidentified ameansofgoingfromhotshutdowntocoldshutdownconditions couldincludefillingofthesteamgenerators andsteamlinessolidwithwater,andusingthemasawater-to-water heatexchanger.

ThismethodhasbeenacceptedasviablebytheNRC.Othermeansofremovingdecayheathavealsobeeninvestigated, anddescribed intheNRC's"SafeShutdownEvaluation" fortheGinnaSEP(September 29,1981report).TheseincludeuseoftheCVCS,RHR,steamgenerator blowdownsystems,andthe"bleed-and-feed"method,usingthepressurizer PORV'sandtheSafetyInjection pumps.Giventheextensive diversity andcapacityoftheGinnaauxiliary feedwater systems,andtheothermethodsavailable foralternative decayheatremovalmeans,RGGEconsiders thatthisissueisbeingadequately addressed fortheGinnaplant,andthatoperation cancontinuewithoutunduerisktothehealthandsafetyofthepublic.34 fta3P1 Unresolved SafetIssueA-46SeismicQualification ofEuimentin0eratinPlantsDescription of'Problem:

IThedesigncriteriaandmethodsfortheseismicqualification ofmechanical andelectrical equipment innuclearpowerplantshaveundergone significant changeduringthecourseofthecommercial nuclearpowerprogram.Consequently, themarginsofsafetyprovidedinexistingequipment toresistseismically inducedloadsandperformintendedsafetyfunctions mayvaryconsiderably amongplantslicensedindifferent timeframes.TheNRCstaffhasdetermined thattheseismicqualification oftheequipment inoperating plantsshouldbereassessed toensuretheabilitytobringtheplanttoasafeshutdowncondition whensubjecttoaseismicevent.TheNRC'sobjective ofthisUnresolved SafetyIssueA-46istoestablish explicitguidelines thatcanbeusedtojudgetheadequacyoftheseismicqualification ofmechanical andelectrical equipment atalloperating plantsinlieuofattempting tobackfitcurrentdesigncriteria.

Thisguidancewillconcernequipment requiredtosafelyshutdowntheplant,aswellasequipment whosefunctionisnotrequiredforasafeshutdown, butwhosefailurecouldresultinadverseconditions whichmightimpairshutdownfunctions.

35-RGGEStatus:TheSystematic Evaluation Program,throughtheSeniorSeismicReviewTeam,performed anauditoftheGinnasafety-related structures, systems,andcomponents.

ThisreportisprovidedasNUREG/CR-1821.

Mostequipment wasfoundtobecapableofwith-standingtheGinnaSSE.Incertainareassufficient documentation wasnotavailable.

Reanalysis and,insomecases,redesignorresupport arebeingconducted.

ThestatusoftheseitemsisprovidedinNUREG-0821.

Inaddition, theanchorage ofmajorequipment wasaddressed.

Experience frommajorearthquakes hasshownthatalmostallseismically inducedequipment failuresinqualityindustrial facilities haveoccurredbecausethecomponents werenotadequately anchoredtotheirfoundations, andthatfewequipment failureshaveoccurredinequipment thatwasanchored.

Asaresultofthereviewofelectrical equipment anchorage, modifications toupgradetheanchorages ofanumberofsafety-related electrical components atGinnaweremade.RG6Eisalsoparticipating inaSeismicQualification UtilityGroupwhichisconducting apilotprogramtoexploreanalternative methodforseismically qualifying selectednuclearplantcomponents basedonexperience withtheequipment duringearthquakes.

ThisprogramisexpectedtoassisttheNRCanditsconsultants indeveloping qualification methodology forinstalled equipment atoperating plants,inscreening andassigning qualification prior-itiesformoreefficentutilization ofNRCandindustryresources, 36

)i<~

andpossiblyinqualifying certainclassesofequipment onagenericbasiswithoutspecifictestingoranalysesofcomponents.

Basedontheabovediscussion, RG6Econsiders thatthisissueisbeingadequately addressed, andthatoperation oftheGinnaplantcancontinuewithoutunduerisktothehealthandsafetyofthepublic.37 14ll Unresolved SafetIssueA-47SafetImlications ofControlSstemsDescription ofProblem:Thisissueconcernsthepotential fortransients oraccidents beingmademoresevereasaresultofthefailureormalfunction ofcontrolsystems.Thesefailuresormalfunctions mayoccurindependently, orasaresultoftheaccidentortransient underconsideration.

Oneconcernisthepotential forasinglefailure(suchaslossofpowersupply,shortcircuit,opencircuit,orsensorfailure)tocausesimultaneous malfunction ofseveralcontrolsystems.Anotherconcernisforapostulated accidenttocausecontrolsystemfailureswhichwouldmaketheaccidentmoreseverethananalyzed.

Accidents couldconceivably causecontrol'systemfailuresbycreatingaharshenvironment intheareaofthecontrolequipment orbyphysically damagingthecontrolequipment.

Althoughitisgenerally believedthatsuchcontrolsystemfailureswouldnotleadtoseriouseventsorresultinconditions thatsafetysystemscannotsafelyhandle,rigorousin-depthstudieshavenotbeenperformed toconfirmthisbelief.RGEEStatus:Theseparation oftheReactorProtection Systemfromnon-safety systemswasthesubjectofSEPTopicVII-l.A.TheSERforthis38

>s Sa+SEPtopicconcluded thattheGinnaplantmetallcurrentlicensing criteria.

Additional studiesprobingtheinteraction ofsafetyandnon-safety systemswereperformed duringGinna'sfireprotection i<treviewsinresponseto10CFR50AppendixR.Withi'ndesignated firezones,itwasassumedthatdamagetoanyequipment (oritscontrolcables,ifaffected) couldcausefailureofanytype(including "hotshorts").

Thededicated shutdownsystemproposedbyRG6Easaresultofthefireprotection studywillincorporate therequiredseparation ofsafetyandnon-safety systems.InresponsetoIEInformation Notice79-22,"Potential Unreviewed SafetyQuestiononInteraction BetweenNon-Safety-Grade SystemsandSafety-Grade Systems,"

RGEEperformed anevaluation ofthesepotential effects.ByletterdatedOctober5,1979,RG&Econcluded thatnoneofthescenarios constituted anunreviewed safetyquestionfortheGinnaplant.Anotherpotential controlandsafetysysteminteraction wasaddressed inRGGE'sresponsetotheNRC'sSeptember 16,1980letterregarding lossofD.C.sourcesandinverters.

RGEE'sinstrumentation busandpowersupplyarrangement issuchthatlossofanyD.C.sourceorinverterwouldnotresultinthelossofanyinstrument buses.Thisisdescribed inourletterofOctober9,1981.39 IIt+~\~lyIII Basedontheinteraction studiesdonetodate,theseparation alreadyprovidedbetweensafetyandnon-safety systems,andproposedfireprotection modifications, RG6Econsiders thatthisissueisbeingadequately addressed, andthatoperation ofGinnacancontinuewithoutunduerisktothehealthand'safetyofthehlpublic.40 t~>ea,1iil.II Unresolved SafetIssueA-48HdroenControl-Measures andEffectsofHdroenBurnsonSafetEuiment.Description ofProblem:Following aLOCAinanLWRplant,combustible gases,princi-pallyhydrogen, mayaccumulate insidetheprimaryreactorcontain-mentasaresultof:(1)metal-water reactioninvolving thefuelelementcladding; (2)radiolytic decomposition ofthewaterinthereactorcoreandthecontainment sump;(3)corrosion ofcertainconstruction materials bythespraysolution; and(4)synergistic

chemical, thermal,andradiolytic effectsofpost-accidentenvironmental conditions oncontainment protective coatingsystemsandelectriccableinsulation.

Intheeventofaseverelydegradedcore,alargeadditional amountofhydrogencouldbegenerated asaresultofthereactionbetweeenthemoltenfuelandtheconcretecontainment base.Othercombustible gasesmayalsobegenerated bythisreaction.

TheaccidentatTMI-2onMarch29,1979resultedinmetal-water reactionwhichinvolvedhydrogengeneration wellinexcessoftheamountsspecified inthecurrentregulations 10CFRSection50.44.Asaresult,itbecameapparenttotheNRCthatadditional hydrogencontrolandmitigation measuresmayneedtobeconsidered forallnuclearpowerplants.41 I>oS~IPJlA,t~l RGGEStatus:TheGinnaplanthasredundant hydrogenrecombiners, whichwouldbeusedtoprevent'he, accumulation ofcombustible mixtureofhydrogengas,in',accordance

.withtheguidanceprovidedinRegulatory Guide1.7.Also,thecontainment purgesystemincludesfilters,andcouldbeusedintheeventofahydrogenbuildup.AsaresultofTMImodifications, redundant hydrogenmonitorshavebeeninstalled.

Thegreatamountofhydrogengenerated atTMI-2wasduetothefailuretomaintainadequateSafetyInjection flow.Basedonintensive trainingofoperators, aswellasprocedural modifications, itisnotexpectedthatthiswouldre-occur.

Further,ithasbeenestimated, duringthereviewsoftheZionandSequoyahcontainments, thatareactorcontainment buildingcouldwithstand pressures 2to3timesdesignpressureforshortperiodsoftimewithoutcatastrophic failure,andthatalargedryreinforced concretecontainment suchasthatusedatGinnaisleastsuscept-ibletohydrogenburnconsiderations becauseofthelargevolumeandhighdesignpressure.

Becauseofthehydrogenmonitoring andcontrolsystemsinplaceatGinna,theextensive procedural andtrainingupgradesasaresultoftheaccidentatTMI-2,andthepressuremarginsavailable atGinna-type containments, RGSEconsiders thatthehydrogenburnissueisbeingadequately addressed, andthatoperation ofGinnacancontinuewithoutunduerisktothehealthandsafetyofthepublic.42 awcH'es<)w'~s Unresolved SafetIssueA-49Pressurized ThermalShockDescription ofProblem:Asaresultofoperating experience, itisrecognized'hat transients canoccurinpressurized waterreactorscharacterized bysevereovercooling causingthermalshocktothevessel,con-currentwithorfollowedbyrepressurization.

Inthesepressurized thermalshock(PTS)transients, rapidcoolingofthereactorvesselinternalsurfacecausesatemperature distribution acrossthereactorvesselwall.Thistemperature distribution resultsinthermalstr'esswithamaximumtensilestressattheinsidesurfaceofthevessel.Themagnitude ofthethermalstressdependsonthetemperature differences acrossthereactorvesselwall.Effectsofthisthermalstressarecompounded bypressurestressesifthevesselisrepressurized.

Severereactorsystemovercooling eventswhichcouldbefollowedbyrepressurization ofthereactorvessel(PTSevents)canresultfromavarietyofcauses.Theseincludeinstru-mentation andcontrolsystemmalfunctions, andpostulated accidents suchassmallbreakloss-of-coolant accidents (LOCAs),mainsteamline breaks(MSLBs),feedwater pipebreaks,orstuckopenvalvesineithertheprimaryorsecondary system.

0pl:I'g1fd Aslongasthefractureresistance ofthereactorvesselmaterialremainsrelatively high,sucheventsarenotexpectedtocausefailure.Afterthefracturetoughness ofthevesselisreducedbyneutronirradiation (andthisoccursatafasterrateinvesselsfabricated ofmaterials whicharerelatively sensitive toneutronirradiation damage),severePTSeventscouldcauseIcrackpropagation" offairly,smal.l.fl'aws thatareconservatively postulated toexistneartheinnersurface.RG&EStatus:Rochester GasandElectricisanactiveparticipant intheWestinghouse OwnersGroup,whichisevaluating thePTSquestions forWestinghouse reactors.

Analysesperformed todateindicatethattheGinnareactorvesselcouldwithstand asevereovercooling event.Sinceanalyseshavedemonstrated thecapability oftheGinnareactorvesseltowithstand severeovercooling transients, andRGEEiscontinuing withtheWestinghouse OwnersGroupandtheNRCtoreachafinalsolutiontothePTSissue,RGGEconsiders thatthisissueisbeingadequately addressed, andthattheGinnaplantcancontinuetooperatewithoutunduerisktothehealthandsafetyofthepublic.44

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