ML17264A281

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Proposed Tech Specs Re Changes to Current RCS Pressure & Temp Limits for Heatup,Cooldown,Criticality & Hydrostatic Testing
ML17264A281
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Site: Ginna Constellation icon.png
Issue date: 12/08/1995
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ROCHESTER GAS & ELECTRIC CORP.
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ML17264A280 List:
References
NUDOCS 9512120159
Download: ML17264A281 (17)
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f%xlJt'7)QQhe.~creactorcoolantpumpinasingleloopisstartedwiththeRCStemperature asmuchas50Flowerthanthesteamgenerator secondary sidetemperature.

Thisresultsinasuddenheatinputtoawater-solid RCSfromthesteamgenerators, creating.th,::*',,-,,"-!::,,

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la'iiiTheresulting massinjection/letdown mismatchcausesanincreasing pressuretransient.

3.2LTOPSSetpointDetermination Rochester GasandElectricandBabcock&WilcoxNuclearTechnology (BWNT)havedeveloped thefollowing methodology whichisemployedtodetermine PORVsetpoints formitigation oftheLTOPSdesignbasiscoldoverpressurization transients.

Thismethodology maximizes theavailable operating marginforsetpointselection whilemaintaining anappropriate levelofprotection insupportofreactorvesselandRHRSystemintegrity.

3.2.iParameters Considered Theselection ofproperLTOPSsetpointforactuating thePORVsrequirestheconsideration ofnumeroussystemparameters including:

a.Volumeofreactorcoolantinvolvedintransient 9512120159 951208PDRADOCK05000244'PPDR3-2 b.RCSpressuresignaltransmission delayc.Volumetric capacityofthereliefvalvesversusopeningposition, including thepotential forcriticalflowd.Stroketimeofthereliefvalves(open&close)e.Initialtemperature andpressureoftheRCSandsteamgenerator f..MassinputrateintoRCSg.Temperature ofinjectedfluidh.Heattransfercharacteristics ofthesteamgenerators Initialtemperature asymmetry betweenRCSandsteamgenerator j~k.secondary waterIMassofsteamgenerator secondary waterRCPstartupdynamics10CFR50,AppendixG'4'ressure/temperature characteristics ofthereactorvessele~~(ti/><m.Pressurizer PORVpiping/structural analysislimitations n.Dynamicandstaticpressuredifferences throughout theRCSandRHRSo.RHRSystempressurelimitsp.Loopassymetry forRCPstartcasesqf:,:;,:.::-:,:,':;::;

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.aetp'oftTheseparameters aremodelledintheBWNTRELAP5/MOD2-BSW computercode(Ref.19)whichcalculates themaximumandminimumsystempressures.

3.2.2PressureLimitsSelection ThefunctionoftheLTOPSistoprotectthereactorvesselfromfastpropagating brittlefracture.

Thishasbeenimplemented bychoosingaLTOPSsetpointwhichpreventsexceeding thelimitsprescribed bytheapplicable pressure/temperature characteristic forthespecificreactorvesselmaterialinaccordance withrulesgiveninAppendixGto10CFR50"'.

TheLTOPSdesignbasistakescreditforthefact3-3

thatoverpressure eventsmostlikelyoccurduringisothermal conditions intheRCS.Therefore, itisappropriate toutilizethesteady-state AppendixGlimit.Inaddition, theLTOPSalsoprovidesforanoperational consideration tomaintaintheintegrity ofthePORVpiping,andtoprotecttheRHRSystemfromoverpressure duringtheLTOPSdesignbasistransients.

Atypicalcharacteristic 10CFR50AppendixGcurveisshownbyFigure3.1wheretheallowable systempressureincreases withincreasing temperature.

ThistypeofcurvesetsthenominalupperlimitonthepressurewhichshouldnotbeexceededduringRCSincreasing pressuretransients basedonreactorvesselmaterialproperties.

Superimposed onthiscurveisthePORVpipinglimitandRHRSystempressurelimitwhichisconservatively used,forsetpointdevelopment, asthemaximumallowable pressureabovethetemperature atwhichitintersects withthe10CFR50AppendixGcurve.Whenareliefvalveisactuatedtomitigateanincreasing pressuretransient, thereleaseofavolumeofcoolantthroughthevalvewillcausethepressureincreasetobeslowedandreversedasdescribed byFigure3,2.Thesystempressurethendecreases, asthereliefvalvereleasescoolant,untilaresetpressureisreachedwherethevalveissignalled toclose.Notethatthepressurecontinues todecreasebelowtheresetpressureasthevalverecloses.

Thenominallowerlimitonthepressureduringthetransient istypically established basedsolelyonanoperational consideration forthereactorcoolantpump¹1sealtomaintainanominaldifferential pressureacrossthesealfacesforproperfilm-riding performance.

Intheeventthattheavailable rangeisinsufficient toconcurrently accomodate theupperandlowerpressurelimits,theupperpressurelimitsare'given preference.

Thenominalupperlimit(basedontheminimumofthesteady-state 10CFR50AppendixGrequirement, theRHRSystempressurelimit,andthePORVpipinglimitations) andthenomirlalRCP¹1sealperformance criteriacreateapressurerangefromwhichthesetpoints forbothPORVsmaybeselectedasshownonp.d..e,',"p,',i*

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-.!.Ii,::.:3-4 3.2.3MassInputConsideration Foraparticular massinputtransient totheRCS,thereliefvalvewillbesignalled toopenataspecificpressuresetpoint.

However,asshownonFigure3.2,therewillbeapressureovershoot duringthedelaytimebeforethevalvestartstomoveandduringthetimethevalveismovingtothefullopenposition.

Thisovershoot isdependent onthedynamicsofthesystemandtheinputparameters, andresultsinamaximumsystempressuresomewhathigherthanthesetpressure.

Similarly therewillbeapressureundershoot, whilethevalveisrelieving, bothduetotheresetpressurebeingbelowthesetpointandtothedelayinstrokingthevalveclosed.Themaximumandminimumpressures reached(P~andP~)inthetransient areafunctionoftheselectedsetpoint(P,)asshownonFigure3.3.Theshadedarearepresents anoptimumrangefromwhichtoselectthesetpointbasedontheparticular massinputcase.Severalmassinputcasesmayberunatvariousinputflowratestoboundtheallowable setpointrange.3.2.4HeatInputConsideration Theheatinputcaseis,donesimilarly tothemassinputcaseexceptthatthelocusoftransient pressurevaluesversusselectedsetpoints maybedetermined forseveralvaluesoftheinitialRCStemperature.

Thisheatinputevaluation providesarangeofacceptable setpoints dependent onthereactorcoolanttemperature, whereasthemassinputcaseislimitedtothemostrestrictive lowtemperature condition only(i.e.themassinjection transient isnotsensitive totemperature).

TheshadedareaonFigure3.4describes theacceptable bandforaheatinputtransient fromwhichtoselectthesetpointforaparticular initialreactorcoolanttemperature.

IftheLTOPSisasinglesetpointsystem,themostlimitingresultisusedthroughout.

3.2.5FinalSetpointSelection 3-5 Bysuperimposing theresultsofmultiplemassinputandheatinputcasesevaluated, (fromaseriesoffiguressuchas3.3and3.4)arangeofallowable PORVsetpoints tosatisfybothconditions canbedetermined.

Forasinglesetpointsystem,themostlimitting setpointischosen,withtheupperpressurelimitgivenprecedence ifbothlimitscannotbeaccomodated.

~It~I~SgadCi<~~tt)oltalsc~i'sit~C.a.httTheselection ofthesetpoints forthePORVsconsiders theuseofnominalupperandlowerpressurelimits.Theupperlimitsarespecified bytheminimumofthesteady-state cooldowncurveascalculated inaccordance withAppendixGto10CFR50'4'r thepeakRCSor:RHRSystempressurebaseduponpiping/structural analysisloads.Thelowerpressureextremeisspecified bythereactorcoolantpump¹1sealminimumdifferential pressureperformance criteria.'-:

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hirtkand)sessdrsaussed':S!sotto'd~ot%%is!:re pa~it-t3.3Application ofASMECodeCaseN-514ASMECodeCaseN-514""allowslowtemperature overpressure protection systems(LTOP)tolimitthemaximumpressureinthereactorvesselto110%ofthepressuredetermined tosatisfyAppendixG,paragraph G-2215,ofSectionXI3-6 oftheASMECode'".(Note,thatthesetpointselection methodology asdiscussed inSection3.2.5specifically utilizesthesteady-state curve,)Theapplication ofASMECodeCaseN-514increases theoperating margininthe,regionofthepressure-temperature limitcurveswheretheLTOPSsystemisenabled.CodeCaseN-514requiresLTOPStobeeffective atcoolanttemperatures lessthan200'Foratcoolanttemperatures corresponding toareactorvesselmetaltemperature lessthanRT>>+50'F,whichever is,greater.RT>>,isthehighestadjustedreference temperature forweldorbasemetalinthebeltlineregionatadistanceone-fourth ofthevesselsectionthickness fromthevesselinsidesurface,asdetermined byRegulatory Guide1.99,Revision2.Althoughexpectedsoon,useofCodeCaseN-514hasnotyetbeenformallyapprovedbytheNRC.Intheinterim,anexemption totheregulations mustbegrantedbytheNRCbeforeCodeCaseN-514canbeusedin'thedetermination oftheLTOPSsetpoint(s) andenabletemperature.

3-7

3.4EnableTemperature forLTOPSTheenabletemperature isthetemperature belowwhichtheLTOPSsystemisrequiredtobeoperable.

Thedefinition oftheenablingtemperature currently approvedandsupported bytheNRCisdescribed inBranchTechnical PositionRSB5-2"".Thispositiondefinestheenabletemperature forLTOPsystemsasthewatertemperature corresponding toametaltemperature ofatleastRT>>+90'Fatthebeltlinelocation(1/4tor3/4t)thatiscontrolling intheAppendixGlimitcalculations.

Thisdefinition ismostlybasedonmaterialproperties andfracturemechanics, withtheunderstanding thatmaterialtemperatures'of Ropy+90Fatthecriticallocationwillbewellup.thetransition curvefrombrittletoductileproperties, andtherefore brittlefractureofthevesselisnotexpected.

TheASMECodeCaseN-514supportsanenabletemperature ofRTgpr+50For200F,whichever isgreaterasdescribed inSection3.3.Thisdefinition isalsosupported byWestinghouse andcanbeusedbyrequesting anexemption totheregulations orwhenASMECodeCaseN-514isformallyapprovedbytheNRC.TheRC8coldlegtemperature limitation forstartinganRCPisthesamevalueastheLTOPSenabletemperature toensurethatthebasisoftheheatinjection transient isnotviolated.

TheStandardTechnical Specifications (STS)prohibitstartinganRCPwhenany'CScoldlegtemperatures islessthanorequaltotheLTOPSenabletemperature unlessthesecondary sidewatertemperature ofeachsteamgenerator islessthanorequalto50'FaboveeachoftheRCScoldlegtemperatures.

3-8 Figure3.1TYPICALAPPENDIXGP/TCHARACTERISTICS (g2500~2000~~15000U0<O1000ClI-Q500O'F/HR100IMPOSEDPORVPIPINGLIMITIMPOSEDRHRSPIPINGLIMIT00100200300400500INDICATED COOLANTTEMPERATURE,

'F3-9 Figure3.2,TYPICAL:PRESSURETRANSIEN7 (3RELIEFVAVL'6CYQLEJ8EfP;OINX-RESETRIfrihr3-10 Figure3.3:(MASSINPUT)::'APPENDIX:G SIAXIMUMLIMIT:,'RCPTGal;:::,'ERFORMAt4R

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ISETPOIN7RANGE:PORVSETPOINT)'.PSIG ThemaximumpressurelimitistheminimumoftheAppendixGlimit,thePORVdischarge pipingstructural analysislimit,ortheRHRsystemlimit3-11 Figure3.4:":.:SRTP:OINK:.

.'::DETERMlfNATION (HEAT:INP UT)'APPENDIX:GSIAXIMUM LIMIT"P.tAN:IIIRCP.N:SEAL:::P.NFQRMANcR CRlTERfA:::::::

SETPOINTRANGE:FORVSETPOIN7):PSIG ThemaximumpressurelimitistheminimumoftheAppendixGlimit,thePORVdischarge pipingstructural analysislimit,ortheRHRsystemlimit3-12

4.0REFERENCES

1.NUREG1431,"Standard Technical Specifications forWestinghouse Pressurized WaterReactors",

Revision0,September, 1992.2.U.S.NuclearRegulatory Commission, "RemovalofCycle-Specific Parameter LimitsfromTechnical Specifications",

GenericLetter88-16,October,1988.3.U.S.NuclearRegulatory Commission, Radiation Embrittlement ofReactorVesselMaterials, ReuiorGuid1.99Revision2,May,1988.4.CodeofFederalRegulations, Title10,Part50,"Fracture Toughness Requirements forLight-Water NuclearPowerReactors",

AppendixG,FractureToughness Requirements.

5.AMEBoileranPrureVeelCde,SectionXI,"RulesforInservice Inspection ofNuclearPowerPlantComponents",

AppendixG,FractureToughness CriteriaForProtection AgainstFailure.6.R.G.Soltesz,R.K.Disney,J.Jedruch,andS.L.Ziegler,NuclearRocketShielding Methods,Modification, UpdatingandInputDataPreparation.

Vol.5-Two-Dimensional DiscreteOrdinates Transport Technique, WANL-PR(LL)-034, Vol.5,August1970.7.ORNLRSICDataLibraryCollection DLC-76SAILORCoupledSelf-Shielded, 47Neutron,20Gamma-Ray, P3,CrossSectionLibraryforLightWaterReactors.

8.ASMEBoilerndPressureVesselCode,SectionIII,"RulesforConstruction ofNuclearPowerPlantComponents",

Division1,Subsection NB:Class1Components.

9.BranchTechnical PositionMTEB5-2,"Fracture Toughness Requirements",

NUREG-0800 StandardReviewPlan5.3.2,Pressure-Temperature Limits,July1981,Rev.1.4-1 C'='lllrA-10.ASTME-208,StandardTestMethodforConducting Drop-Weight TesttoDetermine Nil-Ductility Transition Temperature ofFerriticSteels,ASTMStandards, Section3,AmericanSocietyforTestingandMaterials.

11.BSWOwnersGroupReportBAW-2202, "Fracture Toughness Characterization ofWF-70WeldMaterial",

B&WOwnersGroupMaterials Committee, September 1993.12.Letter,ClydeY.Shiraki,NuclearRegulatory Commission, toD.L.Farrar,Commonwealth EdisonCompany,"Exemption fromtheRequirement toDetermine theUnirradiated Reference Temperature inAccordance withtheMethodSpecified in10CFR50.61(b)(2)(i)(TACNOS.M84546andM84547)",

DocketNos.50-295and50-304,February22,1994.13.CodeofFederalRegulations, Title10,Part50,"Fracture Toughness Requirements forLight-Water NuclearPowerReactors",

AppendixH,ReactorVesselMaterialSurveillance ProgramRequirements.

14.Timoshenko, S.P.andGoodier,J.N.,ThorofElaicit,ThirdEdition,McGraw-HillBookCo.,NewYork,1970.15.ASMEBilerandPresurVesselCode,SectionXI,"RulesforInservice Inspection ofNuclearPowerPlantComponents",

AppendixA,AnalysisofFlaws,ArticleA-3000,MethodForK,Determination.

FerriticMaterials",

WeldingResearchCouncil,NewYork,August1972.17.ASMEBoilerandPressureVesselCodeCaseN-514,SectionXI,Division1,"LowTemperature Overpressure Protection",

Approvaldate:February12,1992.18.BranchTechnical PositionRSB5-2,"Overpressurization Protection ofPressurized WaterReactorsWhileOperating atLowTemperatures",

NUREG-0800 StandardReviewPlan5.2.2,Overpressure Protection, November1988,Rev.2.4-2 19.BWNT,"RELAPS/MOD2, AnAdvancedComputerProgramforLight-Water ReactorLOCAandNon-LOCATransient Analysis,"

BAW-10164P-A.

4-3

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