ML18025A492

Susquehanna Units 1 and 2 - Letter Attaching an Interim Report on Potential Deficiency Which Was Discussed with Mr. Heishman on March 6, 1975

ML18025A492
Person / Time
Site:	Susquehanna
Issue date:	04/04/1975
From:	Curtis N W Pennsylvania Power & Light Co
To:	O'Reilly J P NRC/IE, NRC Region 1
References
Download: ML18025A492 (6)

Text

~yPP:..IL.~TWONORTHNINTHSTRSPT,AllENTOWN,PA.18101PHONE)(215)821-5151April4,1975Qc~ulat'ogMr.JamesP.O'ReillyDirector,OfficeofXnspectionandEnforcementU.S.nuclearRegulatoryCommission631ParkAvenueKingofPrussia,PA1/406SUSQUEHANNASTEAMELECTRICSTATIOHIIG'ERXiIRT'iMTOilPOTENTIALDEFICIENCY"R1OO450FXLE840-4PLA-60

DearMr.O'Reilly:

InaccordanceT~ithlOCFR50.55(e),attached.aretvocopiesofaninterimreportonapotentialdeficiencyTThichTTasdiscussedwithyourMr.Heishmanont~farch6>1975.Verytrulyyours,'N.CurtisVicePresident-EngineeringEcConstructionSworntoandsubsciibedbeforemethis~2$oi,'/',1975NotaryPublicMyCommissionExpires:P4~,li~<Q)P.c-Mr.DonaldF.KnuthDirectorOfficeofXnspectionandEnforcementU.S.huclearRegulatoryCommissionWashington,DC20555~g'fi(1~PSNNSYlVANIAPOWER8,lIGHTCOMPANY

/~~DATEPomtTIAL'DEFICX...:CrIDitTX"IED':!!arch.6,1975FACILITY:SusquehannaSteamElectricStation,Units1and2TOPICOFXi~isIbfH"PORT:Additionalloadshavebeenidentifidwhichshould,beconsideredinthedesignofthesuppressionpoolstructuresandequipment.Themagnitudeofthese'loadsandtheirapplicabilitytotheSSESdesignbaseshavenotbeendetermined.SCOP""OFIliTEHD<H"PORT:Asrequiredby1OC."-H50.$$(e)thisinterimreportissubmittedtodescribeapotentialdeficiencywhichmayhaveacversea<ectsontneSusquehannaSteamElectricStationUnits1and.2(SSES).Thisrepot.alsoadvisestheCommission'fthephenomenainvolved,providesapreliminaryindicationofimplications,anddescribescorrectiveactionunderway.XDEbTIFXCATIONOFPO'x~itTXALDEFICIT'FACY:TheprimarycontainmentdesignbasesandloadcombinationsdescribedintheSSESPSAHSections5.2.2andC.2.6donotexplicitlyincludethefollowingphenomena:1)SvppressionPoolSwell2)ContainmentVentPipeHorizontalLoadsfromsteamcondensation3)bhinSteamSafety/ReliefValvedischargepipeairclearingThesephenomenawerepeviouslye'theconsiderednotlimitingorwereconsiderednotrelevanttotneSSES.'KXXpressuesuppressioncontainment.TworecentlettersfromGeneral.ElectricCompany(NSSSvendor)toBechtelPowerCorporation(ArchitectEngineer)identifyinformati6nthathasbeendevelopedfromtheParkXXXPressureSuppressionTestFaci3,ity(PS":)and"hich-maybeapplicabletotheSSESContainment.Thephenomenaandtheirimplicationsaredescribedbelow.DESCRIPTIO~iiOFFrZ)40'..-iA:Twogroupsofphenomenahavebeenidentified:Onegroupoccursasaresultofthepostulatedlossofcoolantaccident(LOCA)wniletheothergroupoccursasaresultoftheactuationofmainsteamsafety/reliefvalves.Itshould.berealizedthatthepreciseloadsapplicabletoSSEShavenotbeenfixedatpresent,however,prelim'naryconservativeestimatesindicatethatportionsoftheexistingdesignmayrequiremodification.IX@AWhentheLOCAoccusthcairinthedry"ellisforceddownthevent,pipesintothesuppressionpool.Thecompressedairbubbleformedattheend.ofeachvent

~~'I VPage2~,0causesthewateinthesuppressionpooltoriseasaligamentwnenthebubbleisformed'ndthenexpands.Asthcbuobleexpandsandr'sesinthepool,theligamentofwaterdecreasesuntilapoinatwhichtnebubblebreaksthroughtheremaininglayerformingaCwophase"froth"ofairandwater.-Str'ucturesandequipmentthatareabovethesuppressionpoolwillbesubjectedtoanimpingementanQ/ordragload.fromthispoolswellaction.Thetypeand'magnitudeofloadisafunctionoftheheightaboveCheinitialwatersurface.Theseloadsarenotapplieddirectlytothefissionproductoarrier.AconservativeextrapolationofthedataavailablefromG"'sHarkXXiverificationtestprograminthePSTFhas'beenpreparedforprclimina>ydeterminationofstructuralloads.Fromthispeliminaryconservativeevaluation,thereareindi-cationsthatsomemoQificationand/orrelocationofequipmentorstructuralmembers",couldberequired.Pipeseismicbracing,drywelltowetwellvacuumbreakers,S/RValvepiping,suppressionpoolhydrogenrecombinersandthediaphragmslabareintheregionaffected.bypoolswell.Followingthepoolswelltransient,Chereisaperiod.ofquasisteadystatesteamflowthroughtheventpipesCothesuppressionpool.informationfromtestingperformedataforeignpressuresuppressioncontainmentindicatesthatthereare'ateralloadswhichoccurontheverticalventpipes.Nhenapplyingaloadwhichwasdeterminedfromboundingthedataavailablefromtheforeigntests,itwasdeterminedthatadditionalbracingfortheventsmayoerequiredtoaccommodatetheload.S/RVALVEDiSCHARGEThedischargepipingofasafety/reliefvalvecontainsnon-condensablecontainmentatmosphereandacolumnofwaterpriortoactuation.Followingsafetyrelief.valveactuationpressurebuildsupinsidethepipingassteamcompressesthenon-condensablesandforcesChewaterfromthcpipe.Theatmospherefollowsthewaterintheformofahighpressurebuoble.Onceinthepool,thebubbleexpandsanalogoustoaspringandacceleratesthesurroundingwaterradiallyoutward.Themomentumofthewatercausesthebuobletooverexpandandthebubblepressurebecomesnegative,ThisnegativepressureslowsdownandfinallyreversesChemotionofthewater,lead'ng'othecompressionofthebubble,andthesequencerepeatsitselfuntilthebuoblereachesthesurfaceofthepool.Tnebubbleoscillationcausespressurethroughoutthesuppressionpoolresultinginoscillatoryloadsonpoolboundariesandsubmergedcomponents.Forpreliminaryevaluation,clearingloadsvereestablishedusingthetechniquepresentedinIKBO-10859.itisfeltChat'theloadsusedwereveryconservative.Thispreliminaryinvestigationindicatesthatsomemodificationtothesafetyreliefvalvedischargep'pingmaybereouired.Thispipingmaybere-routedtominimizethemagnitudeofthepressureoscillationsonthelinerplateo"itmaybenecessarytochangetheconfigurationoftheendofthepipetobreakupthehighpressureairbubble.

M~en'loadsspecificallya~U.cabletoSSESduetothesephenomenaaredefined.areviewofadequacyoftheSSESdesignfeatureswillbemade.STATUSOFTiEPROD..CTTheconstructionofSSESisapproximately10$.complete.Thesuppressionpool.baseslabsandlinerplatesarecompleteandinplace.TheUnit1reactorsupportpedestalanditslinerplatearecompleteuptothediaphragnslabandarealsoinplace.TheUnit1suppressionpoolrebariscompleteandinplacewhiletheUnit2suppressionpoolrebarisbeingfabricated.InstallationofstructuralsteelandrebarfortheUnit1diaphragmslabisnearly'complete.CORRECTIVEACTIONKG)ERdAYAnintensiveeffortbyPPM,BechtelandGeneralElectricCo.tobetteridentifytheloadsduetothesephenomenaisunderway.Thepreliminarytasksofdevelopingaplanforresolutionoftheseissuesandaschedulenavenearlybeencompleted.klorkisproceedingonthedevelopmentofmathematicalmodelstodetermine'd+amicloadfactorsandtogenerateloaddata.iniswillbeaugmentedbyatestprogramwhichisapplicabletoverificationofthemathematicalmodels'developed,Thelasttaskwillbetodeterminetheva.iousloadsfortheSSEScontainment,todetermineloadcombinationstobeused,and.tocompleteanyrequired.designchanges.AschedulefortheseactivitieswillbesubmittedtotheiTRCinthenearfuture.PPMwillkeepthe'ommissioninformedofdevelopmentsasaresultof.theworkunderwayoConcretepoursandothercriticalactivitiesinvolvingtheContainmentwillbesuspendedunt'1necessarymodificationsinthisareahavebeenidentified.PriortoresumingconstrueionofanyaffectedportionoftheContain.",.,nt,theproposed.modificationswillbereviewedwiththeHRC.

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