ML17037C242

Nine Mile Point Unit 1 - Letter Responding to the November 30, 1973 Letter Concerning the Extent and Consequences of Possible Inverted Poison Tubes in the Control Blades and Requiring Further Action Be Implemented within 15 Days After Recei

ML17037C242
Person / Time
Site:	Nine Mile Point
Issue date:	04/09/1974
From:	Skovholt D J US Atomic Energy Commission (AEC)
To:	Schneider R R Niagara Mohawk Power Corp
References
Download: ML17037C242 (4)

Text

DocketNo.50-220HiagaxaMohawkPowerCorporation ATTN:Hr.R.R.Schneider VicePxesidont

-ElectricOperations 300ErieBoulevard PestSyracuse, NewYork13202Gentlemen:

APRg)g74Distribution DocketFileAECPDR.LocalPDRBranchReadingJRBuchanan, ORNLDJSkovholt, L:ORTJCarter, L:ORACRS(16)RO(3)OGCDLZiemann, L:ORBif/2CJDeBevec, L:ORBII2JLSapir,L:ORB//2RH)iggs,L:ORBII2SVarga,L:RPInaletterdatedNovember30,1973,yousubmitted information concerning theextentandconsequences ofpossibleinvertodpoisontubesinthecontrolbladesoftheNineMilePointUnit1reactor.Hehavereviewedyoursubmittal alongwiththeassociated GeneralElectricgenericsub-mittaldatedOctober8,1973,andhaveconcluded thatwithoutadditional supporting evidencetheassumption ofahomogeneous dofectrateof5Xisnot)ustified.

Inaddition, relatively smallgroupings ofdefective bladescanpxoducethemaximumundesirable effects.Therefore, tomaintainthecurrentsafetymarginrequirements untilaninspection ofthexodsisperformed, wearerequiring thatthefollowing actionbeimplemented within15daysafterreceiptofthisletter.1.Subtractavalueof0.2Xdeltakfromthecurrentallowable insequence controlrodreactivity worth.2.Addavalueof10psitothemaximumpressurecalculated forthesafetyvalvesizingpressurization transient andconfirmthatadequatemarginexists.3.Establish aprocedure toreportanyobservedreactivity anomalygreaterthan0.5XtotheAECwithin10daysoftheobservation.

Itisimportant thatuncertainties associated withthepossiblepresenceofdefective controlbladesbeeithersignificantly reducedoxeliminated assoonaspracticable.

Youshould,therefore, inspectahomogeneous samplingofabout50Xormoreofthecontrolrodsduringthenextrefueling outageandcompletetheinspection oftheentirecorewithinthenexttworefueling outages.

llIII NiagaraMohawkPowerCorporation APRg797yIfthecalculated potential shutdmmmarginloss(assuming fullsettlinginalltheobservedinvertedpoisontubes)extrapolated toincludeuninspected rodsislessthan0.5Xdeltak,addthecalculated valueto0.25/deltaktoobtaintheminimumshutdownmarginrequirement forthefollowing fuelcycle.Youmayxeducetheminimumshutdownmarginrequire-mentsbythecalculated xeactivity uncertainty removedbythereplacement.

ofdefective blades.Iftheresultsoftheinspection yieldapotenti.al equivalent full-core shutdownmarginlossgreaterthan0.51deltak,inspection resultsshouldbesubmitted totheAECforreviewbefoxetheendoftheoutageandsomeamountofbladereplacement mayberequired.

Basedupontheinspection x'esultsandanybladereplacements, subsequent restrictions oninsequence contxolrodxeactivity worthsandpressuremarginswillbead)ustedtoreflectknowncoreconditions.

Intheinterim,westronglyencourage theperformance of-aninservice inspection ofcontrolrodsduringanyshutdownofsignificant durationbeforeyournextrefueling outage.Sincerely, DonaldJ.SkovholtAssistant DirectorforOperating ReactorsDirectorate ofLicensing cc:J.BruceHacDonald, EsquireDeputyComnd.ssioner andCounselNewYorkStateDepartment ofCommerce-andCounseltotheAtomicEnergyCouncil99Washington AvenueAlbany,NewYork12210AxvtnZ.Upton,EsquireLeBoeuf,Lamb,Leiby5HacRae1757NStreet,N.W.Washington, D.C.20036Dr.WilliamGeymouxStaffCoordinator NewYorkStateAtomicFnergyCouncilNewYorkStateDepartment ofCommerce112StateStreetAlbany,NewYork12207Anthony?'.Roisman,EsquireBerlin,RoisnanandKessler1712NStreet,N.W.Washington, D.C.20036OswegoCi.tyLibraryX740YSURHAM23v'ATCW L:ORB//JLSapir:sg4/8/74L:ORBI/CJDeBcIJgP~L:0DLZiemann c,lflwL:0DJoholt4//7'4PormhEC-3ld(Rev.9.33)hECM0240CI'0CA2IO1IA00I$20204 lC=