ML18005A803

LER 89-004-00:on 890207,loss of All Three Circulating Water Pumps Resulted in Loss of All Flow to Main Condenser, Causing Reactor Trip.Caused by Air Entering Circulating Water Pump Seal Water Sys.Components repaired.W/890309 Ltr

ML18005A803
Person / Time
Site:	Harris
Issue date:	03/09/1989
From:	Lew G, Watson R CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
HO-890032-(O), LER-89-004, LER-89-4, NUDOCS 8903160060
Download: ML18005A803 (9)

Text

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Ac CE~ RATED D1SlBUTJ 0> DE M 04 STR+04 SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8903160060 DOC.DATE: 89/03/09 NOTARIZED- NO DOCKET I FACIL:50-400 Shearon Harris Nuclear Power Plant, Unit 1, Carolina 05000400 AUTH. NAME AUTHOR AFFILIATION LEW,G.T; Carolina Power & Light Co.

WATSON,R.A. Carolina Power & Light. Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 89-004-00:on 890207,reactor trip/turbine trip on loss of condenser vacuum caused by loss of CCW circulation pumps.

W/8 ltr.

DISTRIBUTION CODE: IE22D COPIES RECEIVED: LTR ( ENCL SIZE:

TITLE: 50.73 Licensee Event Report (LER), Incident Rpt,Qetc.

NOTES:Application for permit renewal filed. 05000400/

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-1 LA 1 1 PD2-1 PD 1 1 BECKER, D 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 ACRS WYLIE 1 1 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 ARM/DCTS/DAB 1 1 DEDRO 1 1 ~

NRR/DEST/ADE 8H 1 1 NRR/DEST/ADS 7E 1 0 NRR/DEST/CEB 8H 1 1 NRR/DEST/ESB 8D 1 1 NRR/DEST/ICSB 7 1 1 NRR/DEST/MEB 9H 1 1 NRR/DEST/MTB 9H 1 1 NRR/DEST/PSB 8D 1 1 NRR/DEST/RSB 8E 1 1 NRR/DEST/SGB 8D 1 1 NRR/DLPQ/HFB 10 1 1 NRR/DLPQ/QAB 10 1 1 NRR/DOEA/EAB 11 1 1 NRR/DREP/RAB 10 1 1 NRR/DREP/RPB 10 2 2 RR/iggIS/SIB 9A 1 1 NUDOCS-ABSTRACT 1 1 REG FZQE~ 02 1 1 RES/DS IR/EIB 1 1 WSgDSR/PRAB 1 1 RGN2 FILE 01 1 1 EXTERNAL EG&G WILLIAMSI S 4 4 FORD BLDG HOY,A 1 1 H ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1 1 S D

NCTE 'IO ALL "RZDS" RECIPIENIS:

S PIZASE HELP US 'IO RECCE WASTE.'XNZACZ 'IHE DOCUMENI'ONSOL DESK, RCCM Pl-37 (EXT. 20079)

LISTS FOR

~ EZZKCNATE YOUR NAME PBCH DISTIGBUTXGN DOCUMEMI'S YOU DGN~T HEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 45 ENCL 44

NAC Form 355 UA. NUCLEAR REOULATOAY COMMISSION (04L) I APPROVED OMB NO. 31504104 EXPIRES: Sl31lSS LICENSEE EVENT REPORT ILER)

FACILITY NAME (1) DOCKET NUMBER (2) PAOE 3 SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 0 5 0 0 04 0 0 1 OFO 6 REACTOR TRIP/TURBINE TRIP ON LOSS OF CONDENSER VACUUM CAUSED BY LOSS OF CONDENSOR COOLING WATER CIRCULATION PUMPS F VENT OAT E (Sl LER NUMBER (Sl REPORT DATE (7) OTHER FACILITIES INVOLVED (5)

MONTH OAY YEAR YEAR SEOUENTIAL &WE NUMBER RE~

NUMBER MONTH OAY YEAR FACILITYNAMES DOCKET NUMBER(S) 0 5 0 0 0 0 2 0 7 89 89 0 0 4 0 003 0 9 8 9 0 6 0 0 0 OPERATINO THIS REPORT IS SUBMITTED PURSUANT To THE AEQUIREMENTs oF 10 cFR ()r fcrrrc4 onr of mare of thr follorffnp) (11)

MODE (0) 20.402(bl 20.405(c) 50.73(e)(2)(lr) 73.71(b)

POWER 20AOS( ~ ) (1)(II SOM(cl (1) 50.73(e) 12)(rl 73.71(c)

LEVEI.

HO) 0 4 7 20.405(e) (I )(Q) 50.35(c) (2) 50,73(e) I 2) (rII) oTHER lsprclfy ln Aotrrct or/ore end In Text, NRC Form 20.405( ~ l(1)()Ill 50.73(e) (2)(l) 50.73(e)(2)(rllll(A) 388A) 20AOS(e)(1)(lr) 50.7 3(e) (2) (5 l 50.73( ~ l(2)(rIII)(Bl r', ..,c@ . g 20.405(e)(1)(rl 50.73(e) (2) (IIII 50.73( ~ l(2)(x)

LICENSEE CONTACT FOR THIS LER (12)

NAME TEI.EPHONE NUMBER AREA CODE G. T. LEW PROJECT ENGINEER REGULATORY COMPLIANCE COMPLETE ONE LINE FOR EACH COMPONENT FAILURE OESCAIBEO IN THIS AEPOAT (13)

'ijv'N' 'x:p xoyXc'cc CAUSE SYSTEM COMPONENT MANUFAC TUAER EPOATABLE TO NPADS CAUSE SYSTEM COMPONENT MANUFAC.

TUAER K 'PORTABLE TO NPRDS h lx y K K' MR A 62 5 N:<% Irm S SUPPLEMENTAL REPORT EXPECf ED (14) MONTH DAY YEAR EXPECTED SUBMISSION DATE (15)

YES llfyrr, complete EXPECTED SV84(ISSION DATE) No ABSTRACT (Limit to 1400 tpecer, l A, rpproxlmerrly flfrrrn tlnpfeepece typewritten linerl (15)

The plant was operating in Mode 1, Power Operation, with Main Feedwater Train "B" in service at 47X reactor power. At 1055 on February 7, 1989, the sudden loss of all three Circulating Water Pumps (CWPs) resulted in the loss of all flow to the Main Condenser. The plant tripped at 1058 as a result of a sudden loss of vacuum in the Main Condenser. The Low Pressure Turbine Rupture Disks ruptured as designed, a result of the loss of vacuum in the Main Condenser.

The Auxiliary Feedwater System actuated subsequent to the reactor trip as a result of trip of the only operating Main Feedwater Pump. Main Steam isolation valves were closed to limit plant cooldown and the plant stabilized in Hot Standby (Mode 3).

This event was caused by air entering the CWP's Seal Water System and causing the pumps to trip on loss of seal flow. Air entered the Seal Water System due to a failure in the level control system for the Potable Water Hydropneumatic Tank.

Corrective actions included repairing failed components in the Potable Water System, replacing the rupture disks for the turbine, identifying additional modifications for the Seal Water System and the Potable Water System.

There was no impact on plant safety. All systems functioned as expected.

This event is reported in accordance with 10CFR50.73(a)(2)(iv) as an Engineered Safety Feature actuation and a reactor protection system actuation.

B9031C 00(' 890309 Z.5~~ I

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PDR ADOCK 0 000400 NI (0

PDC

NRC Sorm 388A US. NUCLEAR REOULATORY COMMISSION (0831 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO OMB NO. 3150M(CO EXPIRES: 8/31/88 SACILITY NAME (Il OOCKET NUMBER (11 LER NUMBER (51 PACE (31 YEAR :(~D> SEQVENTI*L -j) RSV>>ION NVM ER NVM OR SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 OF

//I'morpho>>ce 0 5 0 0 0 TEXT N reevke4 coo o(BOo>>////IC fcem 388AB/(17(

DESCRIPTION:

On February 7, 1989, the plant was operating in Mode 1, Power Operation, at 47X reactor power. Rod Control was in manual and Main Feedwater Train "B" (EIIS:SJ) was in service. Repairs to the Main Feedwater Pump "A" were in progress (refer to LER 89-03 for details).

EVENT:

At about 1030 the "CIRC WTR PUMP (EIIS:KB) A BEARING COOLING WATER LOW FLOW" Alarm was received in the Main Control Room. An operator was dispatched to investigate and check the pump valve line up. At about the same time, personnel in the Radwaste Control Room were investigating reports of air in the Potable Water (PW) System (EIIS:KK).

At 1055 all three Circulating Water Pumps (CWPs) tripped within 9 seconds of each other on low bearing water flow. Condenser (EIIS:SG) pressure began to increase and the operators started a turbine (EIIS:TA) runback at 40 MW per minute. Condenser Vacuum Pumps (EIIS:SH) subsequently tripped (probably due to high discharge temperatures) and were restarted several times over the next few minutes. The trip of the CWPs resulted in decreasing efficiency of the secondary plant. As a result, reactor power began to increase because the turbine was demanding increasing amounts of steam to maintain the selected turbine load.

At 1055:36 CWP."A" was restarted; a start attempt could not be performed until the pump's discharge valve was fully shut from the previous pump trip. The pump ran for only about one minute before tripping on low bearing water flow. An attempt was also made to start CWP "C", but an interlock prevented its start until 60 seconds after the CWP "A" starts Direction was given by the Shift Foreman to monitor condenser vacuum closely and to manually trip the plant when the Turbine Low Vacuum pretrip annunciator was received. The Shift Foreman also dispatched an operator to locally monitor vacuum from the gages located on the turbine's front standard and provide reports to the Main Control Room via radio.

At 1057:45. CWP "C" was started but this action was too late to avoid a plant trip. The turbine tripped automatically on low vacuum moments after the pretrip annunciator was received. The turbine trip was followed by an automatic reactor trip since reactor power was greater than the P-10 permissive of 10K. The Low Pressure Turbine Rupture Disks ruptured as a result of the rapid and sustained loss of circulating water flow and increasing condenser pressure. The plant responded to the trip as expected.

Main Feedwater Pump "B" tripped on low flow when the Main Feed Regulating Valves (EIIS:SJ) shut and the Auxiliary Feedwater System (EIIS:BA) subsequently actuated as required. Main Steam Isolation Valves (EIIS:SB) were NRC SORM 3OOA *U.S.GPO:10850824 538/455 (0831

NRC Form 358A UA. NUCLEAR REOULATORY COMMISSION (0431 LICENSEE EVENT REI5ORT ILER) TEXT CONTINUATION APPROVEO OMS NO. 3)50W104 EXPIRES: 8/31/88 FACILITY NAME 111 OOCKET NUMSER (1) LER NUMSER (8) PACE IS)

CCOVCNTIAL r)cvrcroN YEAR jj~ NVM CII .I NUM cn SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 OF 0 5 0 0 0 TEXT II!more 4/rece/4 /I)r/kraf, ore eO//R/One/I HRC %%drrn JRLCS/ 117)

EVENT: (continued) shut to limit plant cooldown. The turbine rupture disks were replaced. After completing the other repairs and calibrations discussed under cause, the plant was restarted and returned to service at 2204 on February 8, 1989.

CAUSE:

The initial plant design used the Potable Water System to provide seal and bearing water flow for starting a CWP. This flow was to satisfy an 11 gpm start permissive interlock. The CWP discharge is used to provide sufficient flow during normal operation (refer to attached drawing). The pump design included a trip when this seal water flow decreased below 6 gpm. The absence of 11 gpm also actuated a Main Control Board annunciator.

Historically, the design provided a marginal amount of seal flow. In 1988, it was documented that the flow available to satisfy the start permissive was marginal and often required jumpers to satisfy the start logic'. Local verification of the flow rates . was done during pump starts. 'he flow available from the CWP "A" and "B" discharge, was not adequate to keep the low flow annunciator out during normal operation. The potable water valves were throttled to clear these annunciators. This led to the situation where the CWPs operation was dependent on successful operation of the PW System.

Air binding of the PW System occurred on the morning of February 7 when a timing switch (Autocon Industries Part Number 56471300) in the Hydropneumatic Tank (EIIS:KK) level control circuit failed. The failure would not allow the Hydropneumatic Tank makeup pumps to start and supply makeup water to the Hydropneumatic Tank. Tank pressure is maintained at 35 to 60 psig by an air supply regulator that. is independent of the level control system. When the level control system failed, the air supply system kept pressure at the design point. As all the water was used up, air was introduced into the entire PW System including the CWP Seal System.

The indication available to the operators, system pressure, was normal throughout the event. There is no sight glass for the tank to assess adequate level. The first indication that the system was being filled with air came from other personnel in the plant.

While CWP "C" was not tied to the PW System, the seal flow is dependent on the discharge pressure of CWP "CNC All three pumps are cross tied via a common discharge block. There are no discharge check valves for these pumps. Each CWP has a motor operated butterfly valve which must close to prevent recirculation of flow through an idle pump. It was determined that CWP "C" tripped during the time when the discharge valves for CWPs "A" and "B" were going closed. During this time interval, the CWP "C" discharge pressure was too low to maintain its required seal flow because its flow was recirculating through CWP "A" and "B" NRC FORM SCCA n U.S.OPO:10884) 824 538/455 1083)

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NRC form 344A US. NUCLEAR REOULATORY COMMISSION (8431 LICENSEE EVENT REPORT ILER) TEXT CONTINUATION tVrfROVED OMB NO, 3(50&(04 EXPIRES: 8/31/88 fACILITYNAME Ol DOCKET NUMBER (3) LER NUMBER (41 ~ AOE (31 IE7Ã SEOVSNTIAL ~Q ASVISION SHEARON HARRIS NUCLEAR POWER PLANT yEAR ~a NVM 4ll o4. NVMSSII UNIT 1 o s o o o 400 89 0 04 0 0 0 4 oF 0 6 TEXT //I moro ofooo*rff/rorS uro I/4/orN////IC fomr 3//SAS/ (17(

CAUSE: (continued)

Subsequent to the plant trip, the accuracy of the Main Control Board indicators for condenser vacuum, local indicators for. condenser vacuum and the calibration of the pressure switches for the low condenser vacuum turbine trip were investigated. The investigation found that there were significant errors in these devices. The errors were such that the operators'ecision to trip the plant upon receipt of the pretrip annunciator, resulted in an automatic trip and rupture of the low pressure turbine rupture disks. However, these instrument errors would not have prevented the plant trip.

The cause for the error of the Main Control Board gages is that the instrument tubing from the condenser to the pressure transmitters is sloped such that moisture is trapped. This causes inaccurate readings and slow gage response. Experience had shown that the pressure transmitters and instrument tubing had to be drained every few hours to obtain reasonable readings. This problem had been identified in mid 1987. An effort to establish a formal program for conducting the draining was initiated in January 1989, but was not in effect.

r The investigation also revealed that all four low vacuum pressure switches had drifted out of calibration and were recalibrated.. The required setpoint is 5 inhg (abs) and the actual switch settings were found to range from 5.5 to 8.7 in hg (abs). The pretrip annunciator is taken from one of these pressure switches. Its normal setting is 4 inhg (abs) and it was presumed to have also been out of calibration since its trip setpoint for the pressure trip had drifted to 7.9 inhg (abs).

ANALYSIS:

There were no safety consequences as a result of this event. All plant systems responded as expected.

The Low Pressure Turbine Rupture Disks are designed to rupture and protect the turbine during an event of this nature, A higher initial power level would not significantly change the course of event. The event would have been shorter and still resulted in a plant trip.

This is the first time the plant has experienced a rapid vacuum .loss caused by an abrupt loss of Circulating Water Flow. In 1987 debris from damaged cooling tower fill material caused a gradual loss of Circulating Water Flow through the Main Condenser and a trip of the condensate pumps due to high discharge temperature. This event resulted in a manual plant trip. Refer to LER 87-,021.

This event is being reported in accordance with 10CFR50.73(a)(2)(iv) as an Engineered Safety System Feature (EIIS:JE) and" Reactor Protection System (EIIS:JC) Actuation.

NRC SORM 344A oU.S.GPO:108%%34 538/455 (9431

NRC Form 355A US. NUCLEAR REOULATORY COMMISSION

$ 431 LICENSEE EVENT REPORT ILER) TEXT CONTINUATION APPROVED OMS NO. 3150&105 EXPIRES: d/31/N FACILITYNAME 111 DOCKET NUMEER 121 LER NUMEER Idl PACE (31 YEAR P(( 55OVCNTIAL NVM ~ II gg IIEVISION NVM dN SHEARON HARRIS NUCLEAR POWER PLANT UNIT l 0 6 0 0 0 OF TEXT ///II>>rd <<>>ro /5 rddo/r<<L I/od <<//h/or>>IHRC Forrrr 3//SAE/117l CORRECTIVE ACTION:

1 ~ The Hydropneumatic Tank (Potable Water) level control circuit was repaired.

2. Air was purged from *the Potable Water and Seal Water Systems and the systems returned to service.

3~ Plant Change Requests were issued to provide the operator with indication of Potable Water level in the Hydropneumatic Tank.

'I 4~ Initiated design action to evaluate the Seal Water Supply to the Circulating Water Pumps to provide for an adequate and reliable source of water.

5 ~ A Temporary Modification was installed to establish an air purge flow to prevent condensation in the instrument sensing line. The Temporary Modification will be evaluated for subsequent incorporation as perma'nent change.

6. Replaced the Low Pressure Turbine Rupture Disks.

7 Repaired and recalibrated vacuum gages that indicated or responded incorrectly.

NIIC SOIIM SddA o U.SGPO: I Odd.Od2d-d38/5dd 15431

COOL I HG TOY/ER PCV 9576 SER'/ICE AIR I PRO (55 10 60 p8lg) 1PY/29

,ARIOUS LS)

YARD P.V!.

SER'/ICES 1P')V~2 W TOOTHEP. C. 0/. PUl"IPS kIYDROP tlEUt'IATIC TANK (6000 gal. POTABLE "/ATER) .

+ NOTE 5PY/1 Pl TYPICAL C. V'.

SEALS PUI"IP SEAL V/ATER ARRAHGt"IEHT BEARINGS .

SOURCE OF PUI IP FROI"I TRIP SIGNAL klYPOC HLOPI HATORS TO E 5, E CENTER FROt"I PUf"IP SYSTEH DESANDER DISCHARGE

" INTE: VALVES FOR PUI"IPS 'A'HD 4- Vi'ATER TREATI"IEHT BUI LDI tlG

'B'ARTIALLYOPEN TO t'IAI STAIN I'IltIIII'IUI1 SEAL C IRCULATII'!GWATER PUI'IPS AHD BEARING 9/ATER FLO'A'.

SEAL WATER SUPPL'( LER 89-004 Page 6 of 6

NAR 0 ~ $ S89 HARRIS NUCLEAR PROJECT P.O. Box 165 New Hill, NC 27562 File Number.'SHF/10-13510C Letter Number: H0-890032 (0)

U.S. Nuclear Regulatory Commission ATTN: NRC Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 DOCKET NO. 50-400 LICENSE NO. NPF-63 LICENSEE EVENT REPORT 89-004-00 Gentlemen.'n accordance with Title 10 to the Code of Federal Regulations, the enclosed Licensee Event Report is submitted. This report fulfills the requirement for a written report within thirty (30) days of a reportable occurrence and is in accordance with the format set forth in NUREG-1022, September 1983.

Very truly yours, v~3 R. A. Watson Vice President Harris Nuclear Project DLT:msb Enclosure cc: Mr. R. A. Becker (NRR)

Mr. W. H. Bradford (NRC SHNPP)

Mr. S. D. Ebneter (NRC RII)

/r/

MEM/LER-89-004/1/OS1

NRC Document Control Desk Page 2 bcc'Mr. R. H. Bassett Mr. C. H. Moseley, Jr.

Mr R. M. Coats Mr. W. R. Ponder Mri Jo M. Collins Mr. A. W. Powell Mr. C. W. Crawford Mr. C. E. Rose Mr. A. B. Cutter Mr. J. R. Sipp Mr. G. L. Forehand Mr. A. L. Stanley Mri C. R. Gibson Mr. D. L. Tibbitts Mrs J. G. Hammond Mr. R. B. Van Metre Mr. J. L. Harness Mr. D. C. Whitehead Mr M. D. Hill Mr, R. L. Winkler Mr. C. S. Hinnant INPO Mr. J. B. Hudson SHEEC Training Mr L. I. Loflin Reference Library Mr. R. E. Morgan SHNPP Reg. Compliance (2)

Mr. T. C. Morton NLS File: H-X-0523 Day File MEM/LER-89-004/2/OS1