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'og Mr.JamesP.O'ReillyDirector, OfficeofXnspection andEnforcement U.S.nuclearRegulatory Commission 631ParkAvenueKingofPrussia,PA1/406SUSQUEHANNA STEAMELECTRICSTATIOHIIG'ERXiIRT'iMTOilPOTENTIAL DEFICIENCY "R1OO450FXLE840-4PLA-60

DearMr.O'Reilly:

Inaccordance T~ithlOCFR50.55(e),

attached.

aretvocopiesofaninterimreportonapotential deficiency TThichTTasdiscussed withyourMr.Heishmanont~farch6>1975.Verytrulyyours,'N.CurtisVicePresident-Engineering EcConstruction Sworntoandsubsciibed beforemethis~2$oi,'/',1975NotaryPublicMyCommission Expires:P4~,li~<Q)P

.c-Mr.DonaldF.KnuthDirectorOfficeofXnspection andEnforcement U.S.huclearRegulatory Commission Washington, DC20555~g'fi(1~PSNNSYlVANIA POWER8,lIGHTCOMPANY

/~~DATEPomtTIAL'DEFICX...:Cr IDitTX"IED':

!!arch.6,1975FACILITY:

Susquehanna SteamElectricStation,Units1and2TOPICOFXi~isIbfH"PORT:Additional loadshavebeenidentifidwhichshould,beconsidered inthedesignofthesuppression poolstructures andequipment.

Themagnitude ofthese'loadsandtheirapplicability totheSSESdesignbaseshavenotbeendetermined.

SCOP""OFIliTEHD<H"PORT:Asrequiredby1OC."-H50.$

$(e)thisinterimreportissubmitted todescribeapotential deficiency whichmayhaveacversea<ectsontneSusquehanna SteamElectricStationUnits1and.2(SSES).Thisrepot.alsoadvisestheCommission'f thephenomena

involved, providesapreliminary indication ofimplications, anddescribes corrective actionunderway.

XDEbTIFXCATION OFPO'x~itTXAL DEFICIT'FACY:Theprimarycontainment designbasesandloadcombinations described intheSSESPSAHSections5.2.2andC.2.6donotexplicitly includethefollowing phenomena:

1)Svppression PoolSwell2)Containment VentPipeHorizontal Loadsfromsteamcondensation 3)bhinSteamSafety/Relief Valvedischarge pipeairclearingThesephenomena werepeviouslye'theconsidered notlimitingorwereconsidered notrelevanttotneSSES.'KXXpressuesuppression containment.

TworecentlettersfromGeneral.ElectricCompany(NSSSvendor)toBechtelPowerCorporation (Architect Engineer) identifyinformati6n thathasbeendeveloped fromtheParkXXXPressureSuppression TestFaci3,ity (PS":)and"hich-maybeapplicable totheSSESContainment.

Thephenomena andtheirimplications aredescribed below.DESCRIPTIO~ii OFFrZ)40'..-

iA:Twogroupsofphenomena havebeenidentified:

Onegroupoccursasaresultofthepostulated lossofcoolantaccident(LOCA)wniletheothergroupoccursasaresultoftheactuation ofmainsteamsafety/relief valves.Itshould.berealizedthatthepreciseloadsapplicable toSSEShavenotbeenfixedatpresent,however,prelim'nary conservative estimates indicatethatportionsoftheexistingdesignmayrequiremodification.

IX@AWhentheLOCAoccusthcairinthedry"ellisforceddownthevent,pipesintothesuppression pool.Thecompressed airbubbleformedattheend.ofeachvent

~~'I VPage2~,0causesthewateinthesuppression pooltoriseasaligamentwnenthebubbleisformed'nd thenexpands.Asthcbuobleexpandsandr'sesinthepool,theligamentofwaterdecreases untilapoinatwhichtnebubblebreaksthroughtheremaining layerformingaCwophase"froth"ofairandwater.-Str'uctures andequipment thatareabovethesuppression poolwillbesubjected toanimpingement anQ/ordragload.fromthispoolswellaction.Thetypeand'magnitude ofloadisafunctionoftheheightaboveCheinitialwatersurface.Theseloadsarenotapplieddirectlytothefissionproductoarrier.Aconservative extrapolation ofthedataavailable fromG"'sHarkXXiverification testprograminthePSTFhas'beenpreparedforprclimina>y determination ofstructural loads.Fromthispeliminary conservative evaluation, thereareindi-cationsthatsomemoQification and/orrelocation ofequipment orstructural members",couldberequired.

Pipeseismicbracing,drywelltowetwellvacuumbreakers, S/RValvepiping,suppression poolhydrogenrecombiners andthediaphragm slabareintheregionaffected.

bypoolswell.Following thepoolswelltransient, Chereisaperiod.ofquasisteadystatesteamflowthroughtheventpipesCothesuppression pool.information fromtestingperformed ataforeignpressuresuppression containment indicates thatthereare'ateral loadswhichoccurontheverticalventpipes.Nhenapplyingaloadwhichwasdetermined fromboundingthedataavailable fromtheforeigntests,itwasdetermined thatadditional bracingfortheventsmayoerequiredtoaccommodate theload.S/RVALVEDiSCHARGE Thedischarge pipingofasafety/relief valvecontainsnon-condensable containment atmosphere andacolumnofwaterpriortoactuation.

Following safetyrelief.valveactuation pressurebuildsupinsidethepipingassteamcompresses thenon-condensables andforcesChewaterfromthcpipe.Theatmosphere followsthewaterintheformofahighpressurebuoble.Onceinthepool,thebubbleexpandsanalogous toaspringandaccelerates thesurrounding waterradiallyoutward.Themomentumofthewatercausesthebuobletooverexpand andthebubblepressurebecomesnegative, ThisnegativepressureslowsdownandfinallyreversesChemotionofthewater,lead'ng'othecompression ofthebubble,andthesequencerepeatsitselfuntilthebuoblereachesthesurfaceofthepool.Tnebubbleoscillation causespressurethroughout thesuppression poolresulting inoscillatory loadsonpoolboundaries andsubmerged components.

Forpreliminary evaluation, clearingloadsvereestablished usingthetechnique presented inIKBO-10859.

itisfeltChat'theloadsusedwereveryconservative.

Thispreliminary investigation indicates thatsomemodification tothesafetyreliefvalvedischarge p'pingmaybereouired.

Thispipingmaybere-routed tominimizethemagnitude ofthepressureoscillations onthelinerplateo"itmaybenecessary tochangetheconfiguration oftheendofthepipetobreakupthehighpressureairbubble.

M~en'loadsspecifically a~U.cable toSSESduetothesephenomena aredefined.areviewofadequacyoftheSSESdesignfeatureswillbemade.STATUSOFTiEPROD..CTTheconstruction ofSSESisapproximately 10$.complete.

Thesuppression pool.baseslabsandlinerplatesarecompleteandinplace.TheUnit1reactorsupportpedestalanditslinerplatearecompleteuptothediaphragn slabandarealsoinplace.TheUnit1suppression poolrebariscompleteandinplacewhiletheUnit2suppression poolrebarisbeingfabricated.

Installation ofstructural steelandrebarfortheUnit1diaphragm slabisnearly'complete.

CORRECTIVE ACTIONKG)ERdAYAnintensive effortbyPPM,BechtelandGeneralElectricCo.tobetteridentifytheloadsduetothesephenomena isunderway.

Thepreliminary tasksofdeveloping aplanforresolution oftheseissuesandaschedulenavenearlybeencompleted.

klorkisproceeding onthedevelopment ofmathematical modelstodetermine

'd+amicloadfactorsandtogenerateloaddata.iniswillbeaugmented byatestprogramwhichisapplicable toverification ofthemathematical models'developed, Thelasttaskwillbetodetermine theva.iousloadsfortheSSEScontainment, todetermine loadcombinations tobeused,and.tocompleteanyrequired.

designchanges.Aschedulefortheseactivities willbesubmitted totheiTRCinthenearfuture.PPMwillkeepthe'ommission informedofdevelopments asaresultof.theworkunderwayo Concretepoursandothercriticalactivities involving theContainment willbesuspended unt'1necessary modifications inthisareahavebeenidentified.

PriortoresumingconstrueionofanyaffectedportionoftheContain.",.,nt, theproposed.

modifications willbereviewedwiththeHRC.

AJI