ML17223B150

LER 91-001-00:on 910304,inadvertent Actuation of Auxiliary Feedwater Sys Channel a Occurred While Performing Routine Surveillance.Caused by Momentary Loss of Power Supply.Power Supply Replaced & Procedures changed.W/910401 Ltr

ML17223B150
Person / Time
Site:	Saint Lucie
Issue date:	04/01/1991
From:	Lauver C, Sager D FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-91-95, LER-91-001-03, LER-91-1-3, NUDOCS 9104080008
Download: ML17223B150 (7)

Text

A( 'CULLKA.LUu L i KLDU I lulb u&lvlulN> 'i iud'4 6 I > 1 j"-ivi REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9104080008 DOC.DATE: 91/04/01 NOTARIZED: NO DOCKET FACIL:50-389 St. Lucie Plant, Unit 2, Florida Power & Light Co. 05000389 AUTH. NAME AUTHOR AFFILIATION LAUVER,C. Florida Power & Light Co.

SAGER,D.A. Florida Power & Light Co.

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 91-001-00:on 910304,inadvertent actuation of auxiliary feedwater sys Channel A occurred while performing routine surveillance. Caused by momentary loss of power supply. Power supply replaced & procedures changed.W/910401 ltr.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR ENCL SIZE:

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

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 NORRIS,Z 1 1 INTERNAL: ACNW 2 2 ACRS 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/LHFB11 1 1 NRR/ DLPQ/LPE B 1 0 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB1 1 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB 7E 1 1 N PLB8D1 1 1 NRR/DST/SRXB 8E 1 1 G 02 1 1 RES/DSIR/EIB 1 1 RGN2 FILE 01 1 1 EXTERNAL: EG&G BRYCE,J.H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MAYS,G 1 1 NSIC MURPHY,G.A 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

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

TOTAL NUMBER OF COPIES REQUIRED: LTTR 33 ENCL 33

P.O. Box 12S, Ft. Pierce, FL 34954-0]2S FPL April 1, 1991 L-9 1-95 10 CFR 50.73 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: St. Lucie Unit 2 Docket No. 50-389 Reportable Event: 91-01 Date of Event: March 4, 1991 Inadvertent Actuation of Auxiliary. Feedwater Components While Performing Monthly Auxiliary Feedwater Actuation S stem Test Due to E i ment Failure 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, D. A. ager Vice esident, St. Lucie Plant DAS GRM kw Attachment cc: Stewart D. Ebneter, Regional Administrator, USNRC Region Senior Resident Inspector, USNRC, St. Lucie Plant II DAS/PSL N394 910408000$ 9l0401 PDR ADOCK 050003S9 S PDR I

Lf an FPL Group coepany

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FPL FacaIniIa o1 U.S. NUCLEAR REGULATORY COMMISSION NRC Form 366 APPROVED OMB NO. 31534104 (8-83) LICENSEE EVENT REPORT (LER) EXPIRES 8ISI/85 FACILITYNAME (1) DOCKET NUMBER (2)

St. Lucie Unit 2 050003891 0 0 4

' (4) Inadvertent Actuation of Auxiliary Feedwater Components While Performing Monthly Auxiliary Feedwater Actuation System Test due to Equipment Failure EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED(8)

MONTH DAY YEAR YEAR S IAL MONTH DAY YEAR FACILITYNAMES DOCKET NUMBER(S)

N/A 0 0 0 0 3 04 9 1 9 1 0 0 1 0 4 0 1 9 1 N/A 05000 THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR:

OPERATING Check one or more of the followin (11)

MODE (9) 20.402(b) 20.405(c) X 50.73(a)(2)(iv) 73.71(b)

POWER 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c)

LEVEL'10) 1 0 0 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER (Specify in Abstract 20.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(viii)(A) below and in Text 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) NRC Form 366A) 20.405(a)(1)(v) 50.73(a)(2) (iii) 50.73(a)(2)(x)

LICENSEE CONTACT FOR THIS LER 12 NAME TELEP ONE NUMBER AREACODE Catherine Lauver, Shift Technical Advisor 4 0 7 4 6 5 - 3 5 5 0 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 13 CAUSE SYSTEM COMPONENT MANUFAC- TURER REPORTABLE TO NPRDS SYSTFM COMPONENT MANUFAC- REPORTABLE TO NPRDS B A J X T 0 3 2 I I I I I I SUPPLEMENTAL REPORT EXPECTED 14 EXPFCTED MONTH DAY YEAR SUBMISSION YES (Ifyes, complete EXPECTED SUBMISSION DATE) X NO DATE (15)

ABSTRACT (Limitto $ 400 spaces. i e. approximately fifteen single-space typewritten lines) (16)

On March 4, 1991 at 1440, an inadvertent actuation of the Auxiliary Feedwater Actuation System (AFAS)

Channel A occurred. Auxiliary Feedwater (AFW) pump 2A started. The steam admission valve from the 2B Steam Generator to the turbine-driven 2C AFW pump opened, starting the 2C AFW pump. A main feedwater isolation valve received a signal to close, but only moved from its full open position before the signal cleared.

Operators returned all components to their normal position. The initiating event was a momentary loss of auctioneered power supplies to Channel A AFAS actuation relays. The actuation occurred while Instrument and Control (l&C) technicians were performing a routine surveillance and had just finished balancing and adjusting power supplies 301A and 302B.

The root cause of this event is equipment failure. One power supply was momentarily unable to pick up load from the other. Power supply 302B was found to be faulty and replaced.

Other corrective actions include: checking other AFAS power supplies; replacing AFAS power supplies with an improved model; remove balancing and adjusting from the monthly surveillance to 18 month (performed when the unit is shut down). These actions will be taken on both uriits.

FPL Facsimile of NRC Form 366 (9-83)

FPL Facslmloor U.S. NUCLEAR REGULATORY COMMISSION NRC Form 366 APPROVEO 0MB NO. 31504104 (063) EXPIRES 6/31/85 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR EQUENTIAL REVISION St. Lucie Unit 2 NUMBER NUMBER 0 50 0 0389 0 0 1 0 0 0 2 0 4 TEXT (lfmore spaceis required, use additional NRC Form 366A's) (17)

On March 4, 1991, Unit 2 was in Mode 1 at 100% power. Instrument and Control (l&C) personnel were performing the Auxiliary Feedwater Actuation System (AFAS) (EIIS:BA) monthly functional test per IBC procedure 2-0700051. I&C personnel had just finished balancing and adjusting Channel A auctioneered power supplies (PS) to Auxiliary Feedwater (AFW) actuation relays when an actuation

~ of Channel A components occurred. Trip Status and Lockout Status lights were lit. Operations received several AFAS related annunciators (EIIS:IB) and noted that the 2A AFW pump had started and the steam admission valve from the 2B Steam Generator (EIIS:SB) to the turbine-driven 2C AFW pump opened and the steam-driven 2C AFW pump started. The discharge valves for these pumps remained closed. At no time did any AFW enter either Steam Generator. A main feedwater isolation valve received a signal to close, but only moved from its full open position before the signal cleared.

According to the Sequence of Events Recorder, the entire actuation time lasted 0.21 seconds.

Operations instructed l8C to stop testing and returned the Plant to its normal configuration. The Plant was stable at 100% power. After extensive troubleshooting, a faulty power supply was replaced March 6, 1991. The AFAS monthly functional test was satisfactorily completed at 1500 on March 8, 1991.

A Task Response Team and the Facility Review Group met to discuss the events and necessary actions. It was determined that the initiating event was the momentary loss of the auctioneered power supplies. In this circuit, two power supplies and two diodes are connected such that the power supply with the greater voltage carries the load for the AFW actuation relays. As the voltages of the two power supplies varies, one power supply will switch the load to the other. Power supply 302B was found to be faulty.

The procedure methodology, requiring balancing and adjusting power supplies PS 301A and 302B, combined with PS 302B failure, momentarily resulted in PS 301A output voltage level below that specified for system operation. The root cause of the event was the failure of one power supply to pick up load from the other power supply.

FPL Facsimile of NRC Form 366 (9-83)

r FPL Frrattrrtlrr ar U.S. ttUCLEAR REGULATORY COMMISSION ttRC Farm 366 APPROVED 0MB tto. 31 500104

+43) ExpIREs 6/3tr65 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR EQUENTIAL REVISION St. Lucie Unit 2 NUMBER NUMBER 0 50 0 0389 0 0 1 0 0 0 30 0 4 TEXT (Ifmore spaceis requt'red, use additional NRC Form 366A's) (17)

This event is reportable under the requirements of 10 CFR 50.73.a.2.iv as an event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature.

The power supplies for Channel A are configured such that the A power supply is auctioneered with the B power supply. After reviewing the procedure and technical manuals, it was determined that parts, including the balancing and adjusting of power supplies, were not intended to be performed monthly and exposed the Plant to the unnecessary risk of a reactor trip or plant perturbation. These steps requiring monthly power supply adjustments were removed from the monthly AFAS surveillance procedure.

At no time during this event was the AFAS unable to perform its intended safety function. The health and safety of the public were not at risk at any time during this event.

1. Operations instructed I&C to stop testing, identified equipment not in normal configuration, and restored plant to previous configuration.

2. I&C personnel tested the two power supplies and replaced the faulty one.

3. Engineering is evaluating the replacement of the AFAS power supplies for both units with an improved model.

4. I&C personnel changed the surveillance procedures to match the testing frequency recommended by the technical manual and required by the Technical Specifications. I&C will suspend at-power AFAS power supply testing and institute an 18 month surveillance procedure.

5. As a generic response to recent difficulties experienced with the AFAS and other sensitive systems, a cross-functional task team has been formed to review past events and to identify improvement opportunities.

Failed Component Identification:

12 Volt DC Power Supply Todd Products Corporation Model SW12-30 FPL Facsimile of NRC Form 366 (9-83)

FPL Facslrnlo ot U.S. NUCLEAR REGULATORY COMM13 SION NRC Form 366 APPROVEO 0MB NO. 31500104 (963) EXPIRES 6/31/85 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITYNAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR EQUENTIAL REVISION St. Lucie Unit 2 NUMBER NUMBER 0500038991 TEXT (Ifmore spaceis required, use additional NRC Form 366A's) (17) 0 0 1 0 0 0 4 0 0 4 Previous AFAS actuations due to equipment failure:

LER 389-90-006 "Inadvertent Actuation of Auxiliary Feedwater Equipment During Monthly Testing due to Test Instrument Malfunction" LER 389-87-001 "Reactor Trip During Auxiliary Feedwater Actuation System Surveillance due to Design Error" FPL Facsimile of NRC Form 366 (9-83)