ML17266A106

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LER 79-030/01T-0:on 790921,discovered as-built Design Specs for Steam Generator Were Not Used by NSSS Vendor to Establish Instrument Span for Measuring Steam Generator Level.No Cause Given.Low Level Trip Setpoint Raised to 39%
ML17266A106
Person / Time
Site: Saint Lucie NextEra Energy icon.png
Issue date: 10/05/1979
From: SCHOPPMAN M A
FLORIDA POWER & LIGHT CO.
To:
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML17207A480 List:
References
LER-79-030-01T, LER-79-30-1T, NUDOCS 7910190346
Download: ML17266A106 (3)


Text

lfl ReportableOccurre335-79-30LicenseeEventReportPagetwo'ADDITIONALEVENTDESCRIPTIONANDPROBABLECONSEUENCESDuringanevaluationofsteamgeneratorlevelsensinginst'rumentationconductedaspartofcompliancewithNRCI&EBulletin79-21,itwasnotedthatthedesignspecificationsofthesteamgeneratorhadbeenusedbytheNSSSvendortoestablishtheinstrumentspanformeasuringsteamgeneratorlevel.Inactuality,theas-builtdimensionsshouldhavebeenemployedforthisdetermination.TheFSARanalysisassumesareactortripduringalossoffeedwateraccidenttooccurwhensteamgeneratorwaterleveldrops50inchesbelowthenormalwaterlevel.Asaresultofusingthedesign(insteadofas-built)steamgeneratordimensions,thelowleveltripsetpointof37Kisinerror(non-conservative)byapproximately2X(4inches)incomparisonwiththeFSARcriteria.TheFSARanalysisdoes,however,alsoassumeaninstrumenterrorof10inchesinanalyzingthelossoffeedwateraccident.ConfirmationwasreceivedfromtheNSSSvendorthatpastoperationwiththesetpointerrordidnothaveaneffectonthesafetyanalysisanddidnotaffectthehealthandsafetyofthepublic.Thiswasthefirstoccurrenceofthistype.ADDITIONALCAUSEDESCRIPTIONANDCORRECTIVEACTIONUseofwrongdimensionsinestablishingthesteamgeneratorlevelsensinginstrumentspanresultedina2Xerrorinthesteamgeneratorlowleveltripsetpoint.Immediatecorrectiveactionwastoinstructthecontrolcenteroperatorsthat,intheeventofalowsteamgeneratorlevelcondition,thereactorwastobemanuallytrippeduponreaching395level.AfterreceiptofNSSSconfirmationoftheplantstaff'sevaluationoftheproperinstrumentspan,theReactorProtectiveSystemsteamgeneratorlowleveltripsetpointwasraisedto39$.