ML17037C098
| ML17037C098 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 06/02/1972 |
| From: | Burt P A Niagara Mohawk Power Corp |
| To: | Skovholt D J US Atomic Energy Commission (AEC) |
| References | |
| Download: ML17037C098 (8) | |
Text
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Ltrreporting anincidenton6-2-72,regarcLin alproblem withtheelectromatic reliefvalves8etransthefollowing:
PLANTNAMES:NineMilePointENCLOSURES:
Consolidated.
Electromatic Reli'efValve6"-Type1525-VX(Drawing)
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NIAGARAMOHAWKPOWERCORPORATION
~~)$)lil&.,NIAGARA',MOHAWKNineMilePointNuclearStationPostOfficeBox32Lycoming, NewYork13093June2,1972Mr.DonaldJ.SkovholtAssistant DirectorforReactorOperations DivisionofReactorLicensing UnitedStatesAtomicEnergyCommission Washington, D.C;20545
DearMr.Skovholt:
Re:Provisional Operating License:DPR-17DocketNo.:50-220ODuringtheannualinspection outageofNineMilePointUnit¹1,whichwillterminate
- tomorrow, June3,1972,aproblemwiththeelectromatic reliefvalveswasdisclosed.
There'arethree6"Consolidated Electromatic ReliefValves,Type1525-VX,installed oneachofthetwosteamlineswithinthedrywellforatotalofsix.Threearerequiredfordepressurization onlossofcoolantaccidentandfivearerequiredtomaintainpressuremarginbetweenpeaktransient pressureandlowestsafetyvalvesettingonturbinetripwithoutbypass.Ononevalve,thelockingscrew,Part¹8onencloseddrawing,hadbecomeunscrewed allowinglockretainerPlate¹7tofallfree(bothpartswererecovered intheturbinestopvalvestrainerbasket).Thispermitted thediscretainer, Part¹6,tocompletely back-outfallingtothebottomofthevalvebody.Inthiscondition, itwouldbeimpossible tobleedenoughsteamfromChamber"C"toopenthevalveasitwouldbewideopentoChamber"A"andwouldnothavethebenefitoftherestricting orificeintheretainerplate.Oneothervalvewasfoundwiththelockingscrew,Part¹8,backedout1/16"butthelockretainerplateanddiscretainerhadnotmoved,therefore thevalvewasoperable.
Tie-wires holdingthelockingscrewswerebrokenonallsixvalves.
O.r Mr.DcealdJ.SkovholtJune2,1972Repairwaseffectedtoallsixvalvesbyremovingthelockingscrew,Part¹8,andlockretainerplate,Part¹7.Intheirplace,four1/4"Vgrooves,1"long,werecutinthejointbetweenthediscretainerandthevalvebodyinsert.Thesewerestitchweldedtogether, Futuremaintenance maybeaccomplished bygrindingoutthestitchweld.Inthismanner,therecanbenoloosepartsonthevalvestodropintothesteamlinesanddependability ofvalveoperation isincreased.
Verytrulyyours,P.AllisterBurtGeneralSuperintendent NuclearGeneration PAB:pwEnclosure IIJ 212220IS231817161514PORTF12lltIewStitchWeld4PlacesE252627928CONSOLIDATED ELECTROMATIC RELIEFVALVE6"-TYPE1525-VXEffectedParts¹4ValveDisc.¹6DiscRetainer¹7LockRetainerPlate¹8LockingScrewWhennormallyclosed,steampressureisequalinChambers"A","B"and"C".Disc4isheldtoseatbygreaterforcein"C"over"B"(difference inprojected areas)andspring.Valveoperateswhenpressurein"C"isdecreased byopeningofpilotvalve.Highertotalforcein"B"thenpushesDisc4awayfromseatallowingsteamtodischarge.
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