ML17348B270

LER 91-006-00:on 911029,AFW Pumps Autostarted Following Low Suction Pressure Trip of Main Feedwater Pump Due to Mechanical Failure of Regulator to Condensate Polishing Vessel Inlet Valve.Cps bypassed.W/911122 Ltr

ML17348B270
Person / Time
Site:	Turkey Point
Issue date:	11/22/1991
From:	Plinkett T, Dawn Powell FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-91-321, LER-91-006-02, LER-91-6-2, NUDOCS 9112060086
Download: ML17348B270 (10)

Text

ACCELERATED DISTRIBUTION DEMONRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR 9112060086 DOC.DATE- 91/11/22 NOTARIZED- NO DOCKET FACXL:50-251 Turkey Point Plant, Unit 4, Florida Power and Light C 05000251 AUTH. NAME AUTHOR AFFILIATION POWELL,D.R. Florida Power & Light Co.

PLINKETT,T.F. Florida Power & Light Co.

RECXP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 91-006-00:on 911029,AFW pumps autostarted following low suction pressure trip of maxn feedwater pump due to D mechanical failure of regulator to condensate polishing vessel inlet valve.CPS bypassed.W/911122 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR 'f ENCL ~ SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 D AULUCK,R 1 1 INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DS P 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB8H3 1 1 NRR/DST/SPLB8D1 1 1 NRR/DST/SRXB 8E 1 1 BEG- FI'L~~~2

'FILM 1 1 RES/DSXR/EIB 1 1 RGN2.' 01 1 1 EXTERNAL: EG&G BRYCE,J.H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 D

.D NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM P 1-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED LTTR 31 ENCL 31

P.O. Box 029100, Miami, FL', 33102-9100 NQV 2 2 1991 L-91-321 10 CFR 50.73 U..S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: Turkey Point Unit 4

.Docket No. 50-251 Reportable Event: 91-006-00 Date of Event: October 29, .1991 Autostart of Auxiliary Feedwater Pumps Following Low Suction Pressure Trip of Main Feedwater Pump Due to Mechanical Failure of the Regulator to the Condensate Polishin Vessel Inlet Valve CV-4-6351D The attached Licensee Event Report 251-91-006-00 is being provided in accordance with the requirements of 10 CFR 50.73 (a)'(2),(iv) to provide notification of the subject event .

Very truly yours, T. F. Plunkett Vice President Turkey Point Nuclear TFP/DPS/ds enclosures cc: Stewart D. Ebneter, Regional Administrator, Regi'on III USNRC, Senior Resident Inspector, USNRC, Turkey Point Plant 9112060086 911122 PDR .ADOCK, 05000251 p~$ 2 S PDR an FPL'roup company

~I LICENSEE EVENT REPORT (LER)

FACILITY NANS ll) DOCKET NUNBER {3) PACE )3)

TURKEY POINT UNIT' 05000251 oF 1 3 Autostart of Auxiliary Feedwater Pumps Following Low Suction Pressure Trip of Main Feedwater Pump Due to Mechanical Failure of the Regulator to the Condensate Polishing Vessel Inlet Valve (CV-4-6351D)

RPT DATE IT) OTHER PACILITIES INV, )S)

EVENT DATE (5) LER NUMBER (6)

DOCKET P )S)

MON YR NAME 10 29'1 91 006 Og 11 2Z 91

)3)

OPERATINC NODE 10 CFR 50.73 A 2 iv POWER LEVEL {10)

OTHER

)Specify in Anetrect belev end in text)

LICENSEE CONTACT FOR THIS LER (12)

David R. Powell, Licensing Superintendent 305-246-6559 CONPLETE ONE LINE POR EACH CONPONENT PAI LURE DESCRIBED IN THIS REPORT )13)

BA 33 E081 N EXPECTED I

SUPPLENENTAL REPORT EXPECTED ) ~ ) SUSHI SSION DATE )15) MONTH DAY YEAR

)if yee, ccnplete EXPECTED SUBNISSION CATE)

ABSTRACT {15)

On October 29, 1991, at 2316 EST, with Unit 4 at approximately 22 percent power, and Unit 3 at 100 percent power, all three auxiliary feedwater (AFW) pumps autostarted following a trip of the only operating main feedwater (MFW) pump for Unit 4. Autostart of the AFW pumps 'is classified as an engineered safety feature (ESF) actuation.

A backwash of the 4 "D" condensate polisher vessel had been initiated just prior to the autostart of the AFW pumps. A plant operator immediately started the 4B MFW pump. At 2323P the three AFW.pumps were secured and returned to standby mode. The NRC was notified of this event in accordance with 10 CFR 50.72 at 0020 EST, October 30, 1991.

The immediate cause of the autostart of the AFW pumps was the trip of the 4A MFW pump upon loss of suction pressure. The loss of suction pressure to the MFW pump was caused by the diversion of condensate flow to the "D" polisher vessel, through the open inlet valve, and through the backwash receiver. The "D" polisher vessel inlet valve, CV-4-6351D, failed to close because of the failure of the valve limit switch.

The limit switch was found to be out of adjustment. The limit switch was adjusted, tested satisfactorily and returned to service.

Operating procedure OP-7001.3, "Condensate Polishing System Power Vessel Operation," is being revised to require a visual verification of the vessel inlet valve closure prior to initiation of backwash.

4k 4i E~

LICENSEXQVENT REPORT (LER) TEXx CONTZNURTZON r FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO.

TURKEY POINT UNIT 4 05000251 91-006-00 02 OF 03 I. EVENT DESCRIPTION On October 29, 1991, at 2254 EST, the Unit 4 output breaker (EL) (BKR) was closed connecting Turkey Point Unit 4 to the Florida Power &

Light (FPL) power distribution system (grid) . Preparations were in progress to backwash the Unit 4 "D" condensate polisher vessel (BA) (VSL) . The main feedwater (MFW) regulator valves (BA) (FCV) were placed in the automatic control mode at 2312 EST with the unit at approximately 22 percent power. At 2316 EST, a condensate trouble alarm, a main feedwater (MFW). pump (BA) (P) lowpolishing suction pressure alarm, and a MFW low flow alarm were received, and the 4A MFW pump (the only Unit 4 MFW pump running) tripped and all three auxiliary feedwater (AFW) pumps (BA) (P) started. Autostart of the AFW pumps is classified as an Engineered Safety Feature (ESF) actuation.

A plant operator. immediately started the 4B MFW pump. At 2323, the three AFW pumps were secured and returned to standby mode. The NRC was notified of this event in accordance with 10 CFR 50.72 (b) (2) (ii) at 0020 EST, October 30, 1991.

II. EVENT CAUSE

a. Immediate Cause The immediate cause of the autostart of the AFW pumps was the trip of the 4A MFW'ump upon loss of suction pressure.

b. Root Cause The loss of suction pressure to the MFW pump was caused by the diversion of condensate flow to the "D" polisher vessel, through the open inlet valve, and through the backwash receiver. The "D" polisher vessel inlet valvei CV 4 6351Dg failed to close due to the failure of the valve limit switch. An examination of the failed limit switch determined the limit switch to be out of adjustment.

III. EVENT SAFETY ANALYSIS A loss of the MFW supply is a previously analyzed event. As a result of these analyses, plant procedures were developed to provide operator guidance in responding to t: he transient conditions produced during operation and to assure that the plant is stabilized in.a safe condition in accordance with the plant Technical this event, steam generator water levels wereSpecifications. maintained within For operating limits. Another MFW pump was started and the AFW pumps were secured and returned to their standby condition in accordance with approved plant procedures.

A post-event review was conducted to assess the proper operation of safety related equipment. This review established that plant parameters responded as expected. Other than the AFW pumps autostart, there were no manual or automatic reactor protection system or engineered safety feature actuations. Engineered Safety

4h 0 LICENSEdRVENT REPORT (LER) TEXT CONTINUATION P FACILITY NAME DOCKET NUMBER LER NUMBER PAGE NO ~

TURKEY POINT UNIT 4 05000251 91-006-00 03 oF 03 Features were designed to prevent by anticipation, or by reducing the severity through quick automatic response, events that could affect the health and safety of the public.

Based on the above, the health and safety of the public were not adversely affected by this event.

IV. CORRECTIVE ACTIONS A. Immediate Corrective Actions

1. The condensate polishing system was bypassed.

2. The limit switch on valve CV-4-6351D was adjusted, tested satisfactorily and returned to service.

3. The remaining Unit 4 condensate polisher vessel inlet valves (CV-4-6351A, B, and C) were checked and found to be operating properly.

B. Corrective Actions to Prevent Recurrence Operating procedure OP-7001.3, "Condensate Polishing System Power Vessel Operation," is being revised to require a visual verification of the vessel inlet valve closure prior to initiation of backwash. This revision is scheduled to be completed by December 15, 1991.

V. ADDITIONAL INFORMATION A. Similar Events None.

B. Additional Information During this event, water and resin beads overflowed the backwash receiver. The resin beads were recovered in the bermed area and collected for proper disposal. Analysis of the water and resin beads showed no radioactivity. Analysis of the water showed that the water was within the required discharge limits for ph.

C. Failed Parts The limit switch for the Valve Operator for Condensate Polisher Vessel inlet valve CV-4-6351D was found to need adjustment.

Manufacturer: Ramcon Model Number: R-2000D-75 Vendor: Ecodyne Graver

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