ML17223B320

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Special Rept:On 911021 & 22,1B EDG Failed During 24 Hr Surveillance Runs.First Failure Caused by Broken Shaft Due to Fatigue at High Stress Location.New Shaft,Of Modified Design,Installed.Run Performed Satisfactorily on 911027
ML17223B320
Person / Time
Site: Saint Lucie NextEra Energy icon.png
Issue date: 11/13/1991
From: SAGER D A
FLORIDA POWER & LIGHT CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-91-310, NUDOCS 9111200215
Download: ML17223B320 (5)


Text

REGULATORY INFORMATION DISTRIBUTION SYSTEM(RIDS)ACCESSION NBR:9111200215 DOC.DATE:

91/11/13NOTARIZED:

NOFACIL:50-335 St.LuciePlant,Unit1,FloridaPower6LightCo.AUTH.NAMEAUTHORAFFILIATION SAGER,D.A.

FloridaPower&LightCo.RECIP.NAME RECIPIENT AFFILIATION DocumentControlBranch(Document ControlDesk)

SUBJECT:

Specialrept:on911021622,1BEDGfailedduring24hrsurveillance runs.Firstfailurecausedbybrokenshaftduetofatigueathighstresslocation.

Newshaft,ofmodifieddesign,installed.24 hrrunperformed satisfactorily 911027.D*s>>@~~*a~

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I~~~L~TITLE:50.73/50.9 LicenseeEventReport(LER),IncidentRpt,etc.NOTES:DOCKET05000335RECIPIENT IDCODE/NAME PD2-2LANORRIS,JINTERNAL:

ACNWAEOD/DOAAEOD/ROAB/DSP NRR/DET/EMEB 7ENRR/DLPQ/LPEB10 NRR/DREP/PRPB11 NRR/DST/SICBSH3 NRR/DST/SRXB SERES/DSIR/EIB EXTERNAL:

EGGGBRYCE,J.H NRCPDRNSICPOORE,W.COPIESLTTRENCL1111221122111122111111331111RECIPIENT IDCODE/NAME PD2-2PDACRSAEOD/DSP/TPAB NRR/DET/ECMB 9HNRR/DLPQ/LHFB10 NRR/DOEA/OEAB NRR/DST/SELB SDPLBSD102RGN2FILE01LSTLOBBYWARDNSICMURPHY,G.A NUDOCSFULLTXTCOPIESLTTRENCL11221111111111111111111111DNOTETOALL"RIDS"RECIPIENTS:

DDPLEASEHELPUSTOREDUCEWASTE!CONTACTTHEDOCUMENTCONTROLDESK,ROOMPl-37(EXT.20079)TOELIMINATE YOURNAMEFROMDISTRIBUTION LISTSFORDOCUMENTS YOUDON'TNEED!TOTALNUMBEROFCOPIESREQUIRED:

LTTR33ENCL33 P.O.Box128,Ft.Pierce,FL34S54-0128 oVfgpgL-91-31010CFR50.36U.S.NuclearRegulatory Commission Attn:DocumentControlDeskWashington, DC20555Gentlemen:

Re:St.LucieUnit1DocketNo.50-335SpecialReportDateofEvents:October21and22,1991EmerencDieselGenerator FailuresTheattachedSpecialReportisbeingtransmitted pursuanttotherequirement ofSt.LucieUnit1Technical Specifications 4.8.1.2.2 and6.9.2.Thisreportprovidesnotification oftwofailuresassociated withthe1BEmergency DieselGenerator duringthe24hoursurveillance runs.Shouldtherebeanyquestions onthisinformation, pleasecontactus~Verytrulyyours,D.A.SagerPlantVicePresident DAS/JWH/kw Attachment cc:StewartD.Ebneter,RegionalAdministrator, RegionII,USNRCSeniorResidentInspector, USNRC,St.LuciePlantDAS/PSL4550-91gpZPlii2002l5 5'il.ij.=.

r"DR(ADOCki05000='35 PDRc(-~!pranFPLGroupcompany

~Fir~Fjiilir",SpecialReport18Emergency DieselGenerator FailuresSt.LucieUnit1wasinMode5andbeginning arefueling outage.At0357onOctober21,1991,the1BEmergency DieselGenerator (EDG)wasstartedforits24hoursurveillance run.TheEDGautomatically trippedat0928onhighdischarge watertemperature.

Theradiatorfanidlerpulleyshaftwasfoundtobesheared.Analysisshowedthatthebrokenshaftwascausedbyfatigueatahighstresslocation.

Anewshaft,ofamodifieddesign,wasinstalled.

Thenewshaftismadeofadifferent materialandhasreducedstressrisersattheshaftdiameterstepstoincreaseshaftfatigueresistance.

Thissurveillance runwasafailureofavalidtest.RG1.108$2.a.3requiresatesttobeperformed atleastoncepereighteenmonthstodemonstrate full-load-carrying capacityforanintervalofnotlessthan24hours.TheEDGranfiveandone-halfhoursbeforetripping.

nF,ilrThe1BEDGwasrestarted at2035onOctober22,1991.Theradiatorfanbeltswerefoundtobeflappingexcessively.

Plantmanagement decidedtoshutdowntheEDGtodetermine thecauseoftheexcessive flapping.

TheEDGwasstoppedat0931onOctober23.Crackswerefoundonthefandrivebeltbearingsupportframe.Evaluation ofthestructure revealedanaturalfrequency atthethirdharmonicoftheEDGrotational speed.Thepresenceofexcitation forcesnearthenaturalfrequency ofthestructure explainsthereducedlifeoftheidlershaftandsupporting frame.Theexcitation isproducedbythetorsional oscillation fromthe12cylinderEDG.Toincreasetheservicelifeofthefancomponents andassociated supportstructure, thecrackswererepairedandstiffener plateswereinstalled.

Theseactionswereperformed onboththe1Aand1BEDGs.Futureplansaretoinstallvibration isolators onthe1Aand1BEDGpowertakeoffshafts.Theseisolators greatlyreducetheamplitude oftorsional vibrations beingtransmitted tothefanassemblyframeandhaveproventobebeneficial onSt.LucieUnit2EDGs.Thislong-term corrective actionwillbeevaluated forimplementation duringthenextrefueling outage.Thesurveillance runstartedonOctober22wasalsoafailureofavalidtest.RG1.108g2.e.7statesthattestsperformed toverifycorrection oftheproblemshouldbeconsidered validtestsandsuccesses orfailures, asappropriate.

Filure,immThesefailureswerethefirstandsecondfailuresofthe1BEDGsinceimplementation oftheRG1.108-based Technical Specifications.

Todate,twentyvalidtestshavebeenperformed.

Thecurrentsurveillance intervalisoncepersevendaysperTechnical Specification 4.8.1.1.The24hourrunwasperformed satisfactorily from2001onOctober27to2011October28,1991.