ML17222A369

LER 88-004-00:on 880630,reactor Tripped on High Pressurizer Pressure.Caused by Loss of Condensate Pump 1B.Balance Relay Replaced,Failure Analysis Testing Performed & Balance Relay Setpoints modified.W/880725 Ltr

ML17222A369
Person / Time
Site:	Saint Lucie
Issue date:	07/25/1988
From:	Conway W, Andrea Johnson FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
L-88-318, LER-88-004-04, LER-88-4-4, NUDOCS 8808030003
Download: ML17222A369 (6)

Text

A.C CELERATED D1FIKBUT10N DEMONSTRA,TION SYSTEM REGULATl INFORMATION DISTRZBUTZOIQYSTEM (RIDE)

ACCESSION NBR:8808030003 DOC.DATE: 88/07/25 NOTARIZED: NO DOCKET FACIL:50-335 St. Lucie Plant, Unit 1, Florida Power & Light Co. 05000335 AUTH. NAME AUTHOR AFFILIATION JOHNSON,A.B. Florida Power a Light Co.

CONWAY,W.F. Florida Power 6 Light Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 88-004-00:on 880630,reactor tripped on high pressurizer pressure. Caused by loss of condensate pump 1B.

W/8 ltr.

DISTRIBUTION CODE: IE22D TITLE: 50.73 Licensee COPIES RECEIVED:LTR Event Report (LER),

L ENCL Incident X

Rpt, SIZE:

etc.

D S

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 TOURIGNYFE 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 AEOD/DOA 1 1 AEOD/DSP/NAS 1 1 AEOD/DSP/ROAB 2 2 AEOD/DSP/TPAB 1 1 ARM/DCTS/DAB 1 1 DEDRO 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 NRR/DRIS/SIB 9A 1 1 NUDOCS-ABSTRACT 1 1 REGUCZK'. 02 1 1 RES TELFORDFJ 1 1 RES/DSIR DEPY 1 1 RES/DSIR/EIB 1 1 R

RES/DSR DEPY 1 1 RGN2 FILE 01 1 1 EXTERNAL EGStG WILLIAMSFS 4 '4 FORD BLDG HOYFA ~

1 1 I

H ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 1 NSIC HARRISFJ 1 1 NSIC MAYSFG 1 1 S h

TOTAL NUMBER OF COPIES REQUIRED: LTTR 46 ENCL 45

NAC Form 344 V.S. NUCLEAR REGULATORY COMMISSION (9 83)

APPAOVEO 0MB NO. 31504101 LICENSEE EVENT REPORT {LER) EXPIRES." SISIIES FACI I.ITY NAME (11 DOCKET NUMBER (2I PAGE 3)

St. Lucie, Unit 1 0 5 0 0 0 3 3 1 OF 0 REACTOR TRIP ON HIGH PRESSURIZER PRESSURE DUE TO TURBINE RUNBACK CAUSED BY LOSS OF 1B CONDENSATE PUMP EVENT DATE (5) LER NUMBER (4) REPORT DATE It) OTHER FACILITIES INVOLVED IS)

MONTH DAY YEAR YEAR SEGUENTIAL i<<% REvreroN DAY FACILITYNAMES DOCKET NVMBERISI NUMBER v '3 NUMEEII MONTH YEAR N/A 0 5 0 0 0 0 6 3 0 8 8 8 8 0 0 4 0 0 0 7 2588 0 5 0 0 0 OPEAATING THIS REtORT IS SUBMITTED PURSUANT 7 0 THE AEOUIAEMENTS OF 10 CFR (): (Chech one or moie ol the loriominll Ill)

MODE I~ I 20402(4) 20A05(c) 50.7$ (.l(2)(N) 73.71(II)

POWER 20AOB(e) (I I(il 50.34(c)(11 50.73(el(2)(v) 7$ .71(cl LEYEL 0 0 II BI 1 20A05 (I l(1 I l ill 50.34(cl(2l 50.73 (e l(2) lvi() OTHER (Soecify in Aortrect oeiorr enrf In Test, NRC form 20A04(e )ill liiil 50.73( ~ l(2)(i) 50.73(el(21(r(B) (A) 3854l 20A04(el(11(iv) 50.7$ ( ~ l(2)(E) 50.73( ~ l(21(rlQI(BI 20A05(e Illl(vl 50.7$ ( ~ l(2HIBI 50.73( ~ )(2)lx)

LICENSEE CONTACT FOR THIS LER (12I NAME TELEPHONE NUMBER 407 465 -3550 AREA CODE A. B. Johnson, Shift Technical Advisor COMPLETE ONE LINE FOA EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFAC EPORTABLE MANUFAC.

TVRER TO NPRDS CAUSE SYSTEM COMPONENT TVRER X SD 61 I 0 5 Y SUPPLEMENTAL REPORT EXPECTED IIE) MONTH DAY YEAR EXPECTED SUBMISSION DATE (15)

YES Ilfy<<, comolete EXPECTED SVdkt(SSIOhl DATEI X NO ABBTRACT IL(mlt to Ie00 roec<<, I e., eooroslmetely I(I<<en Nnoie rnece tyferrrinen lin<<I (14)

ABSTRACT On June 30, 1988, St. Lucie Unit One was operating at 100 percent power steady state in Mode l. At 0548 hours0.00634 days <br />0.152 hours <br />9.060847e-4 weeks <br />2.08514e-4 months <br />, St. Lucie Unit One experienced a main turbine runback to 60 percent power due to the loss of the 1B Steam Generator Feed Pump (SGFP). The 1B SGFP tripped due to an interlock with the running condensate pump that tripped on its equipment protective relay. The 1B Condensate Pump tripped on a Current Balance Relay actuation. The reactor automatically tripped on high pressurizer pressure. The trip was uncomplicated and the unit was quickly stabi,lized in Hot Standby, Mode 3.

The root cause .for the 1B Condensate Pump to trip was a spurious actuation of its Current Balance Relay.

The following corrective actions have been implemented: replaced the Current Balance Relay, failure analysis testing on the relay will be performed, modified the Current Balance Relay setpoints for both 1A and 1 B Condensate Pump motors to reduce sensitivity to spurious actuation, and a Request for Engineering Assistance has been initiated to perform a study on the necessity of the Current Balance Relay and means to prevent unnecessary condensate pump trips.

8808030003 880725 PDR ADOCK 05000335 .

S PNU NAC Form 344 (9 83 i

NRC FBNB 366A U.S. NUCLEAR REGULATORY COMMISSION

)$ 43)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO OMB NO. 3150WI04 I

EXPIRES: 8/31/88 FACILITY NAME (I) OOCKET NUMBER Il) LER NUMBER (6) PAGE (3)

YEAR AX SEOVENTIAL NUMBER ~

'.8 REVBIION NUMBER St. Lucie, Unit 1 0 8 8 004 0 0 0 2 OF 5 0 0 0 TEXT /// moro Boded /d ror)Ir/rod, I/)B Bddi)r'orro/HRC Form 3//843/ (17)

DESCRIPTION OF EVENT On June 30, 1988, St. Lucie Unit One was operating at 100 percent power steady state in Mode l. There were no evolutions or surveillances in progress.

All automatic controllers were in automatic with the exception of the Control Rod Drive System (EIIS:JD) which was in "OFF".

At 0548 hours0.00634 days <br />0.152 hours <br />9.060847e-4 weeks <br />2.08514e-4 months <br />, the 1B Condensate Pump (EIIS:SD) tripped causing the 1B Steam Generator Feed Pump (SGFP) (EIIS:SJ) to trip by interlock with the 1B Condensate Pump. The loss of the 1B SGFP initiated a main turbine runback (EIIS:JJ) to 60 percent power. The Reactor Control Operator (RCO) alerted to the event by various annunciator alarms (EIZS:IB) attempted to restart the 1B Condensate Pump, but the pump failed to restart. . Primary temperature and pressure were increasing rapidly due to the mismatch between reactor power and turbine power caused by the main turbine runback. Approximately 30 seconds into the transient, the Reactor Protective System (RPS) (EZIS:JC) initiated an automatic reactor trip on high pressurizer pressure (EIZS:JC) at 2400 psia.

The trip was an uncomplicated trip and all systems functioned normally.

The Power Operated Relief Valves (PORV) (EZIS:AB) received the same input signals as the RPS trip bistable to actuate the valves at 2400 psia, however, the, PORVs did not relieve the primary system pressure because their associated block valves were closed due to PORV seat leakage. The peak pressure of the Reactor Coolant System (RCS) (EIIS:AB) during the transient was approximately 2400 psia and did not challenge the Pressurizer Code Safeties (EIZS:AB).

The Steam Bypass Control System (SBCS) (EZISEJI) operated to reduce primary average temperature (T-avg) to the zero power setpoint of 532 degrees F.

Auxiliary Feedwater (EIIS:BA) was manually initiated to control steam generator levels for RCS heat removal. The manual initiation of Auxiliary Feedwater was initiated prior to the completion of the time delay logic for automatic actuation of Auxiliary Feedwater via Auxiliary Feedwater Actuation Signai (AFAS) (EIIS:JE). AFAS actuated on low steam generator (S/G) level. The standard post trip actions were completed with all safety functions verified and the unit was quickly stabilized in Hot Standby, Mode 3.

CAUSE OF EVENT The cause of the main turbine runback was the SGFP trip. The SGFP tripped due to an interlock associated with the running condensate pump. The condensate pump tripped on a spurious actuation of its Current Balance Relay. Following the unit trip, the Electrical Maintenance Department and Florida Power &

Light System Protection Group commenced extensive troubleshooting of the 1B Condensate Pump motor, breaker, electrical transfer switch, and protective circuits. No abnormalities were discovered. The root cause of the relay actuation was determined to be a spurious actuation.

U NRC FORM SddA (94)3)

NRC For~ 366A U.S. NUCLEAR RECULATORY COMMISSION (8-63)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO OMB NO, 3160&)04 EXPIRES: 8/31/88 FACILITY NAME (I) OOCKET NUMBER (2) LER NUMBER (6) PACE (3)

YEAR SEQUENTIAL REVISION St. Lucie, Unit 1 NUMBER NUMBER o s o o o 3 3 5 8 0 0 4 0 0 3 OF 0 4 TEXT /I/mttt tptct /t /tqIt/)td, IItt tdd dd/M/ I/RC Fdmt 36//A'/ (17)

ANALYSIS OF EVENT This event is reportable under 10 CFR 50.73 (a)(2)(iv), "any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESF), including the Reactor Protection System (RPS)".

The loss of the 1B Condensate Pump was a result of a spurious actuation of the Current Balance Relay. The purpose of this relay is to provide protection of the condensate pump motor against the following conditions: an open phase, phase unbalance, or ground fault conditions. The 1B SGFP tripped as expected due to an interlock associated with the 1B Condensate Pump. This interlock is designed to trip the SGFP upon losing the associated Condensate Pump when total feed flow is greater than 50 percent and both SGFPs are running.

The loss of the 1B SGFP resulted in a main turbine runback and a reduction in normal feedwater flow. The main turbine runback is initiated when one of the two running SGFPs trip and the main turbine load is greater than 60 percent. The main turbine runback is not required for reactor safety and is intended to reduce main steam load in response to reduced feedwater flow and subsequent decrease in steam generator water inventories. If the main turbine runback failed to initiate, the RPS would have automatically tripped the reactor on low S/G level ensuring minimum inventory needed for adequate RCS heat removal with sufficient time available for the Auxiliary Feedwater System to supply water to the steam generators. The Auxiliary Feedwater System was available during the entire event.

The Power Operated Relief Valves (PORV) had been placed in the blocked condition by having their associated block valves closed due to seat leakage of the PORVs. For a Loss of Feedwater type of accident, no credit is taken in the updated Final Safety Analysis Report (PSAR) for the automatic actuation of the PORVs to relieve primary system pressure; therefore, having the PORVs blocked did not contribute to the event. The configuration is allowed in accordance with Technical Specifications.

This event was observed to be a routine reactor trip on high pressurizer pressure. The resulting transient was well enveloped by the St. Lucie Unit One updated Final Safety Analysis Report (FSAR) section 15.2.8 "Loss of Normal Feedwater Flow". All Plant Safety Functions were met and there were no additional complications. At no time during the event were the health and safety of the public endangered.

NRC FORM 366A (883)

NRC Fora.3SSA U.S. NUCLEAR REOULATORY COMMISSION I IP&3P LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO OMB NO, 3150&)04 EXPIRES: B/31/SB FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (SI PACE (3)

YEAR SEOUENTIAL REVISION g NUMSSR NUMBER St. Lucie, Unit 1 0 5 0 0 o 3 3 5 8 8 0 0 4 0 0 4 OF 04 TEXT llfmare spsse is /er/Ir/sed, Irse sddr)/orM/AIRC Form 3SBI('s) (Il)

CORRECTIVE ACTIONS

1. Meggered the 1B Condensate Pump motor, breaker, electrical transfer switch, and tested protective circuits. No abnormalities were found.

2. Replaced the Current Balance Relay.

3. The Current Balance Relay will be sent to the relay vendor for Failure Analysis testing.

4. As directed by System Protection Group and General Engineering, the Current Balance Relay setpoints were modified for both 1A and 1B Condensate Pump motors to reduce the sensitivity to spurious actuation.

5. A Request For Engineering Assistance was initiated to perform a study on the necessity of the Current Balance Relay and to identify means to prevent unnecessary Condensate Pump trips.

ADDITIONAL INFORMATION Com onent Information:

Manufacturer: ITE Current Balance Relay Model IISITE 46D Previous Similar Events:

LER 335-87-013 is similar to this event with the exception to the initiating event. The event was caused by the loss of the 1B Steam Generator Feed Pump (SGFP).

NRC FORM SSSA (94)3)

P. O. BOX 14000, JUNO SEACH, HL 33408 %20 J.UhY. 2 5 1988 L-88-318 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: St. Lucie Unit 1 Docket: No. 50-335 Reportable Event: 88-04 Date of Event: June 30, 1988 Reactor Trip on High Pressurizer Pressure Due to Turbine Runback Caused b Loss of 1B Condensate Pum The attached Licensee Event Report is being submitted pursuant to the requirements of 10 CFR 50.73 to provide notification of the subject event.

Very truly yours, W. F. Conw Senior Vice President Nuclear WFC/GRM/cm Attachment cc: Dr. J. Nelson Grace, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, St. Lucie Plant GRMRTLER ME 2-~

/jg an FPL Group company