Information Notice 1993-51, Repetitive Overspeed Tripping of Turbine-Driven Auxiliary Feedwater Pumps

Repetitive Overspeed Tripping of Turbine-Driven Auxiliary Feedwater Pumps

ML031070374
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	07/09/1993
Revision:	0
From:	Grimes B K Office of Nuclear Reactor Regulation
To:
References
IN-93-051, NUDOCS 9307010233
Download: ML031070374 (12)

r -UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555July 9, 1993NRC INFORMATION NOTICE 93-51: REPETITIVE OVERSPEED TRIPPING OF TURBINE-DRIVENAUXILIARY FEEDWATER PUMPS

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert addressees to the problem of repetitive tripping of turbine-driven auxiliary feedwater pumps (TDAFWPs) at the South Texas Project ElectricGenerating Station. It is expected that recipients will review theinformation for applicability to their facilities and consider actions, asappropriate, to avoid similar problems. However, suggestions contained inthis information notice are not NRC requirements; therefore, no specificaction or written response is required.

Description of Circumstances

On December 27, 1992, Houston Lighting & Power Company (the licensee)performed a monthly surveillance test on its Unit 1 TDAFWP. After receiving astart signal, the pump immediately tripped on an overspeed condition. Theoperators repeated the surveillance test after a successful local manualstart. On this attempt the pump successfully started, and the licenseesubsequently considered the pump operable.On January 23, 1993, Unit 2 tripped from 100-percent power on low water levelin one of the steam generators. The trip occurred because electro-hydrauliccontrol oil to the steam generator main feedwater pump turbine was lost. TheUnit 2 TDAFWP started on demand and was later secured when no longer required.After the pump was secured, problems occurred when operators attempted torelatch MOV-514 (the TDAFWP trip/throttle valve) from the control room. (SeeFigure 1.) The pump was declared inoperable. The licensee conducted asignificant amount of troubleshooting and testing on the TDAFWP to resolve theMOV-514 relatch problem and another speed control problem that was identifiedduring the testing. After the operability surveillance test was completedsuccessfully, the TDAFWP was declared operable and the unit was restarted onJanuary 25, 1993.On January 28, 1993, the Unit 1 TDAFWP was tested as part of a routine monthlysurveillance. When started, the TDAFWP immediately tripped on an overspeedcondition and was subsequently declared inoperable. From January 28 through9307010233 P 9t PC w3 -oSI 915I

-IIN 93-51July 9, 1993 January 30, 1993, the licensee undertook an extensive testing andtroubleshooting effort to determine the cause of the problem with the TDAFWP.Numerous pump starts were completed. Several problems (overspeed tripping,lack of speed control, oscillations, and inability to maintain rated full-load, steady-state speed) were identified. On January 30, 1993, the Unit 1TDAFWP was declared operable following extensive maintenance activities andthe successful completion of the surveillance test.On February 1, 1993, the Unit 1 TDAFWP was tested again at the direction ofthe Unit 1 operations manager in order to ensure operability, considering thenumerous problems encountered previously. After receiving a start signal, thepump tripped on an overspeed condition and was declared inoperable.On February 3, 1993, Unit 2 was operating at 100-percent power. Two steam-driven steam generator main feedwater pumps and one electric startup feedwaterpump were providing feed flow to the steam generators. The startup feedwaterpump tripped when the pump lubricating oil duplex strainers were beingshifted. Operators began to manually ramp down power but were unable to avoidthe low steam generator level. The operators subsequently initiated a manualreactor trip before receiving an automatic reactor protection system tripsignal on low steam generator level. Following the plant trip, the Unit 2TDAFWP received an automatic signal to supply water to the steam generators.The pump started but immediately tripped on an overspeed condition.On February 4, 1993, Unit 1 commenced a shutdown to place the reactor in themode required by the Technical Specifications because the TDAFWP had not beenrestored to an operable condition within the outage time allowed by theTechnical Specifications.Further details can be found in License Event Report 50-498/93-007 and NRCInspection Reports 50-498; 50-499/93-05 and 50-498; 50-499/93-07.DiscussionAlthough the licensee did not identify the root cause of the Unit 1 TDAFWPoverspeed trips, the proximate cause was determined to be the intrusion ofwater into the TDAFWP turbine that adversely affected its performance.However, this cause was effectively masked for several surveillance testsbecause the surveillance test program established to satisfy the operabilityrequirements of the Technical Specifications was not sufficiently rigorous toassure that the testing was performed under suitable environmental conditions.The TDAFWP was not returned to its normal standby condition before each of theTDAFWP surveillance tests performed on December 27, 1992, andJanuary 30, 1993. Because of this, the pump was not tested in its normalstandby condition and degraded conditions affecting operability were notreveale IN 93-51July 9, 1993 The licensee determined that the root cause of the February 3, 1993, Unit 2TDAFWP overspeed trip was an incorrect valve lineup in conjunction with anInoperable or degraded steam trap. The valves and the steam trap are locatedin the drain line from the steam admission line. (See Figure 1.) The TDAFWPoverspeed trip was caused by excessive condensate buildup in the steam supplyline upstream of the trip/throttle valve (MOV-514 in Figure 1). The excessivecondensate had accumulated because the steam trap bypass valve, MS-517, wasincorrectly positioned (closed) and the steam trap had degraded to such anextent that it was no longer capable of passing condensate to the condenser.The licensee took the following corrective actions related to the hardwaremodifications for both units:* The trip/throttle valves and governors were sent to the respectivevendors for complete refurbishment and testing. The gearing arrangementof the trip/throttle valve was modified to ensure slower stroke time,thus enabling a more positive governor response.* The TDAFWP drain system was modified to remove the steam traps in thesteamline drain system, replacing them with a spool piece. Also, thetrip/throttle valve high-pressure steam leakoff was separated from theturbine casing drain line and rerouted to the sump to prevent possibleintrusion of steam into the turbine casing. (See Figure 2.)Related Generic Communications* NRC Information Notice 86-14, Supplement 2, "Overspeed Trips of AFW,HPCI, and RCIC Turbines," dated August 26, 1991.* NRC Information Notice 88-09, "Reduced Reliability of Steam-DrivenAuxiliary Feedwater Pumps Caused by Instability of Woodward PG-PL TypeGovernors," dated March 18, 1988.* IE Information Notice 86-14, Supplement 1, "Overspeed Trips of AFW, HPCI,and RCIC Turbines," dated December 17, 1986.* IE Information Notice 86-14, "PWR Auxiliary Feedwater Pump TurbineControl Problems," dated March 10, 198 * .IN 93-51July 9, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts: Mark A. Satorius, RIV(817) 860-8141William D. Johnson, RIV(817) 860-8148Peter C. Wen, NRR(301) 504-2832

Attachments:

1. Figure 1, Existing South Texas ProjectTDAFWP Steam Supply and Exhaust System2. Figure 2, Modified South Texas ProjectTDAFWP Steam Supply and Exhaust System3. List of Recently Issued NRC Information Notices MOV-143STEAM EXHAUSTLINESTEAM ADMISSIONLINEMOV-514TERRYTURBINE(STEAM ADMISSIONLINE DRAINVALVESPIPE CAP WITH ORIFICEIf (UNIT I ONLY)MS371MS370FO 7537B~1I IFO 7537A--YlMS TURBINE CASING373 DRAIN VALVESTEAM TRAPBYPASSVALVESTEAMTRAPw I1°% I'-(D% %D n0D wI-a%0 rCONDENSERFIGURE 1TDAFWP STEAM SUPPLY AND EXHAUST SYSTEM (UNMODIFIED)

MOV-143STEAM EXHAUSTLINESTEAM ADMISSIONLINEMOV-514TERRYTURBINECSTEAM ADMISSIONUNE DRAINVALVESMS370FO 7537BMS TURBINE CASING373 DRAIN VALVEMS515STEAM TRAPBYPASSVALVESPOOLPIECEm 'z--~HAQ %D t" MD3%O D" DWa "MS516CONDENSERFIGURE 2TDAFWP STEAM SUPPLY AND EXHAUST SYSTEM (MODIFED)

Attachment 3IN 93-51July 9, 1993 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to93-5093-4993-4892-06,Supp. 193-47Extended Storage ofSealed SourcesImproper Integration ofSoftware into OperatingPracticesFailure of Turbine-Driven Main FeedwaterPump to Trip Because ofContaminated OilReliability of ATWSMitigation Systems andOther NRC-Required Equip-ment not Controlled byPlant Technical Specifica-tionUnrecognized Loss ofControl Room AnnunciatorsPotential Problem withWestinghouse Rod ControlSystem and InadvertentWithdrawal of A SingleRod Control Cluster AssemblyDegradation of ShutdownCooling System PerformanceOperational ChallengesDuring A Dual-UnitTransientUse of InappropriateLubrication Oils inSafety-Related Applications07/08/9307/08/937/6/9307/01/9306/18/936/10/9306/16/9306/15/9306/10/93All licensees authorizedto possess sealed sources.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor Westinghouse (W)-designed nuclear powerreactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.93-4693-4593-4493-43OL = Operating LicenseCP -Construction Permit

\,-IN 93-51July 9, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.orig /s/'d by BKGrimesBrian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:Mark A. Satorius, RIV(817) 860-8141William D. Johnson, RIV(817) 860-8148Peter C. Wen, NRR(301) 504-2832

Attachments:

1. Figure 1, Existing South Texas Project TDAFWPSteam Supply and Exhaust System2. Figure 2, Modified South Texas ProjectTDAFWP Steam Supply and Exhaust System3. List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEOFFICE *OGCB:DORS *DRP:RIV *TECH ED. *SC:DRP:RIV *D:DRP:RIVNAME PCWen/vsb l MASatorius MFMejac WDJohnson ABBeachDATE 06/01/93 l 06/02/93 06/02/93 06/04/93 06/04/93*PM:PDV:NRR *C:SPLB:DSSA:NRR *D:DSSA:NRR *C:OGCB:DORS:NRR DLEKokaJko CEMcCracken ACThadani GHMarcus dd____06/08/93 06/09/93 06/10/93 06/16/93DOCUMENT NAME: 93-51.IN IN 93-xxJune xx, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:Mark A. Satorius, RIV(817) 860-8141William D. Johnson, RIV(817) 860-8148Peter(301)C. Wen, NRR504-2832

Attachments:

1. Figure 1, Existing South Texas Project TDAFWP SteamSystem2. Figure 2, Modified South Texas Project TDAFWP SteamSystem3. List of Recently Issued NRC Information NoticesSupply and ExhaustSupply and Exhaust*SEE PREVIOUS CONCURRENCEOFFICE *OGCB:DORS *DRP:RIV *TECH ED. *SC:DRP:RIV *D:DRP:RIVN.ME PCWen/vsb MASatorius MFMejac WDJohnson ABBeachDATE 06/01/93 06/02/93 06/02/93 06/04/93 06/04/93*PM:PDV:NRR l *C:SPLB:DSSA:NRR *D:DSSA:NRR C:OGCB:DORS:NRR DLEKokaiko CEMcCracken l ACThadani GHMarcus( r lines06/08/93 1 06/09/93 06/10/93 06//6/93 06/,z/93DOCUMENT NAME: INTDAFWP.WP 6 IN 93-xxJune xx, 1993 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:Mark A. Satorius, RIV(817) 860-8141William D. Johnson, RIV(817) 860-8148Peter C. Wen, NRR(301) 504-2832

Attachments:

1. Figure 1, Existing South Texas Project TDAFWP Steam Supply and ExhaustSystem2. Figure 2, Modified South Texas Project TDAFWP Steam Supply and ExhaustSystem3. List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEOFFICE *OGCB:DORS *DRP:RIV *TECH ED. *SC:DRP:RIV *D:DRP:RIVNAME PCWen/vsb MASatorius MFMejac WDJohnson ABBeachDATE 06/01/93 06/02/93 06/02/93 06/04/93 06/04/93PM PDV:NRR P e E BC:OGCB:DORS:NRR D:DORS:NRRLEKokaiko CEMcCI J dThadani GHMarcus BKGrimes06/1 /93 06/ "/93 06/f/L93 06/ /93 06/ /93DOCUMENT NAME: INTDAFWP.WPl 06-S12-1119 14t130..106/04/93 15:05;301 5 34 37R I'J US NRC FTS 728-327'3NRC WHZTEl LINT F002P.02IN 93-xxJunt Xx, 1993 rhis iofwmtion notice requires no specific act on or written response. Ifyew ton & questions about the information in his notice, please contact*a of tochnical contacts listed bolow or th appropriate Office ofbtlw lector Regulation (NRR) project managerToc"ial contatts:Brian K. Gripes, DirectorDivision of OPerating Reactor SupportOffice of Nuclear Reactor RegulationMKrk A. Satorius, RI'(817) 660-4141William D. Johnton, RIV(817) B6O-814BPeter C. Win NRR(301) 504-28i2fttocwtsz:11. fig" It Existing South Texas Project TDAfWP Steam Supply9 t1. FlKrp 2, Modified South Texas Project TDA4I P Steam SupplyS. stoe.ist tf Recently Issued NRC Information Noice~sand Exhaustand ExhaustIQ2I fIaCURR E _.__ I___-(, 0 1 93PCmn/sb tSu:D~ohnn-/0ul __ 06/02/931 0/P3 OS .6 / .CttKn-ANtrRRD OSZiARR9C OCt!R!OOR$:tRRDe:nRS!NRR-------- -IACHhadani Marcus bKoritmeU- a 0r:w : 1"TuAokIrP IN 93-xxJune xx, 1993Page 3 ofThis information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Reactor RegulationTechnical contacts:Mark A. Satorius, RIV(817) 860-8141William D. Johnson, RIV(817) 860-8148Peter C. Wen, NRR(301) 504-2832

Attachment:

List of Recently Issued NRC Information Notices_. __IOFFICE OGCB:DORS DRP:RIV TECH ED. SC:DRP:RIV D:DRP:RIVNAME PCWen/vsb MASatorius A. WDJohnson ABBeachDATE .06/ I /93 _ 06/ /93 06/-L193 f06/ /93 l 06/ /93....BC:SPLB:DSSA:NRRD:DSSA:NRRBC:OGCB:DORS:NRRD:DORS:NRRCEMcCracken ACThadani GHMarcus BKGrimes06/ /93 06/ /93 06/ /93 06/ /93UMUWMMI NAMt: IN IUDAWFW. WF