ML17348B482

LER 92-004-00:on 920326,reactor Trip Occurred,Resulting in Train B SI & Train B Containment Phase a Isolation.Caused by Worn Test Switch & Procedural Inadequacy.Switch Replaced & Procedure revised.W/920424 Ltr

ML17348B482
Person / Time
Site:	Turkey Point
Issue date:	04/25/1992
From:	Knorr J, Plunkett T FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-92-115, LER-92-004-01, LER-92-4-1, NUDOCS 9205040292
Download: ML17348B482 (10)

Text

ACCELERATED DEMONSTTION SYSTEM DISTRIBUTION REGULATORY INFORMATION DISTRIBUTION SYSTEM,(RIDS)

ACCESSION NBR:9205040292 DOC.DATE: 92/04/25 NOTARIZED: NO DOCKET J$

FACIL:50-251 Turkey Point Plant, Unit 4, Florida Power and Light C 05000251 AUTH. NAME AUTHOR 'FFILIATION KNORR, J. E. Florida Power & Light Co.

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

RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 92-004-00:on 920326,reactor trip occurred, resulting in Train B SI & Train B containment Phase A isolation. Caused by D worn test switch & procedural inadequacy.Switch replaced &

procedure revised.W/920424 ltr.-

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR Q ENCL J, SIZE:

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

NOTES:NRR RAGHAVAN,L 05000251 A D

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL D PD2-2 LA AULUCK,R 1

1 l.

1 PD2-2 PD 1 1 INTERNAL: ACNN 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DS P 2 2 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 RE 1 1 RES/DSIR/EIB 1 1 R(j 1 1 EXTERNAL EG&G BRYCE I J ~ H '3 3 L ST -LOBBY NARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1 NSIC POOREJW 1 l. NUDOCS FULL TXT 1 1 NOTES". 1 1 D

/

A D

D NOTE TO ALL "RIDS" RECIPIENTS:

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

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

ik P.O. Box 029100, Miami, FL, 33102-9100 FPL APR ",.:.1992pppg( ~~

L-92-115

~ 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: 92-004-00 Reactor'rip Due to Failure of Switch in Containment High Pressure Reactor Trip and Safety Injection Initiation Lo ic.

The attached Licensee Event Report 251-92-004-00 is being provided in accordance with 10 CFR 50.73 (a) (2) (iv) .

If there are any questions please contact us.

Very truly yours,

~gp Pl~et& ly~id. +co~~

T. F. Plunkett Vice President Turkey Point Nuclear TFP/jEK/jk enclosures cc: Stewart D. Ebneter, Regional Administrator, Region II, USNRC, Ross C. Butcher, Senior Resident Inspector, USNRC, Turkey Point Plant 9205040292 920425 PDR ADOCK 0500025i S PDR g(pe%'

0 f '

LICENSEE EVENT REPORT (LER)

FACILITY NAME (1) DOCKET NUMBER (2) PAGE (3)

TURKEY POINT UNIT.4 05000251 1 oF 3 TITLE (4) Reactor Trip Due to Failure of Switch in Containment High Pressure Reactor Trip and Safety Injection Initiation Logic.

EVENT DATE (5) LER NUMBER(6) RPT DATE (7) OTHER FACILITIES INV (8)

MON DAY YR YR SEO 6 Ri MON DAY YR FACZLITY NAME'S

'DOCKET 6 (S) 03 26 92 92 '04 00 04 25 '2 TURKEY POINT UNIT 3 05000250 OPERATING MODE (9)

POWER LEVEL (10) 28 10 CFR 50..73 a 2 iv LICENSEE CONTACT FOR THIS LER (12)

James E. Knorr, Licensing Engineer TELEPHONE NUMBER 305-246-6757 1

COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13 CAUSE SYSTEM COMPONENT MANUFACTURER t NPRDS2 CAUSE SYSTEM COHPONFNT MANUFACTURER NPRDS2 JE BLK 'G080 SUPPLEMENTAL REPORT EXPECTED (14) NO X YES 0 EXPECTED SUBMISSION DAY YEAR DATE (15)

(If yes, cenylete EXPECTED SUBMISSION DATE)

ABSTRACT (16)

On March 26, 1992, Unit 4 was operating at approximately 28% power. At 1015

-hours, during the performance of Procedure OP 4004.4, "Containment Isolation Racks QR50 and QR51 Periodic Test," a reactor trip occurred. All systems responded as designed.

During the completion of OP 4004.4, the two out of three actuation logic was completed but the train 4B initiation signal was not blocked. As a result, a B train Safety Injection, and a B train Containment Phase A Isolation was initiated, followed by an automatic reactor trip.

The cause of the event was a worn test switch resulting in a contact "race" between the actuating contact set and the blocking contact set in the test switches. A contributing cause was a procedural inadequacy.

Corrective actions include switch replacement and a procedure revision.

0 FACILITY NAME LICENSEE TURKEY POINT UNIT 4

~ REPORT DOCKET NUMBER 05000251 (LER) TEXT LER NUMBER 92-004-00

(+TIEUATIOE PAGE NO.

02 OF 03 I, EVENT DE SCRIP TXON On March 26, 1992, Unit 4 was operating at approximately 28% power in the process of returning to powero'fafter a power reduction. At 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br />, during the performance Procedure OP 4'004.4, "Containment Isolation Racks QR50 and QR51 Per'iodic 'Test," a reactor trip occurred. All systems responded as designed.

OP 4004.4 is used to complete the surveillance for the Containment High Pressure initiation of Safety Injection and Containment Phase A Isolation. Steps 1 through 4 of the OP 4004.4 test data sheet were performed without incident. Performance of item 1 in Step 5 of the procedure requires the depression of two switch buttons (TS-1 and TS-3 on QR-51) (EIIS JE)(IEEE Component BLK) to simulate the actuation of two out of three channels of High Containment Pressure while simultaneously blocking the initiation of Safety Injection and Containment Phase A Isolation. At '1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br /> during this process the two out of three actuation logic for train 4B was completed, but the train 4B signal was not blocked. As a result, a B train Safety Injection, and a B train Containment Phase A Isolation initiated and an automatic reactor trip occurred.

Step 5 of OP 4004 ' is the first step which tests the two out of three logic for the 10% High Containment Pressure initiation of Safety Injection and Phase A Containment Isolation. The step calls for the operator,to depress two test push buttons "in pairs." Each pushbutton has two contact sets, one 'actuates the logic, while the other blocks the High Containment Pressure signal. For this step to be successful, the switch blocking contacts must be opened either prior to, or simultaneously with, the actuation contacts.

Testing in the instrument rack revealed that the actuating contacts on all three pushbutton switches (TS-1, TS-2, and TS-3) operated prior to the blocking contacts'herefore, if the buttons were pushed at exactly the same time, it is possible that both channels would actuate prior to the blocking of one of the channels. The TS-1 switch showed a travel difference of 0.027 inches between the, actuate and block contact sets' new switch revealed no measurable travel difference between the contact sets. The TS-1 actuate contact set also demonstrated a tendency to stick in the open position due to a sticking contact arm.

II. EVENT CAUSE

.The cause of the event was a switch contact "race" between the actuating contact set and the blocking contact set of test switches TS-1 and TS-3. The outcome of the "race" may have been assured by the sticking actuating contact set on TS-1 which could have been stuck open since step 4 of OP- 4004.4. Both the switch travel difference and sticking contact arm problems appear to be due to wear.

A contributing cause was" the test directions in step 5 of OP 4004.4.

Step 5 instructs the operator to push the buttons in "pairs." Had the step instructed the switches to be depressed in a "push first hold push second" manner, the block logic of the first channel would have operated prior to the actuation of the second channel of the two out of three actuation logic. Since at least one block logic would be completed, the trip would not have occurred.

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LICENSEE ZNT REPORT (LER) TEXT TINVATION FACILITY NAME DOCKET NOMBER LER NOMBER PAGE NO ~

TURKEY POINT UNIT 4 05000251 92-004-00 03'F 03 ZZZ ~ EVENT SAFETY ANALYSZS A reactor trip and subsequent shutdown after an inadvertent safety injection is within the design basis of Turkey Point. The switch.

failure which occurred in this event did not prevent the actuation of a reactor protection system or engineered safety feature due to the failure to block the Containment High Pressure signal. The surveillance testing of the Containment High Pressure signal was a surveillance required by Technical Specifications and is provided for in the design of the plant. The switch failure during the surveillance in this case resulted in a safety injection initiation and reactor trip. The reactor trip occurred after the initiation signal and the plant systems responded" as designed with no actual injection into the vessel. Therefore, there was no compromise of the safety of plant personnel or the public as a result of this switch failure.

CORRECTZVE ACTZONS 1 ~ The test switches in instrument racks QR50 and QR51 for Unit 4 have been replaced.

2. Procedure OP 4004.4 has been revised to avoid simultaneous switch operation and to confirm switch contact status via status lights and test indicating lights. Procedure 4004.4 has been successfully performed for racks QR50 and QR51 on Unit 4.

3 Walkdowns have been performed on other systems to identify other

~

switch applications of this type. The applications found have been evaluated to determine if switch replacement is in order. No potential problems were found except for instrument racks QR50 and QR51 on Unit 3.

4. Switches on Unit 3 instrument racks QRSO and QR51 will be replaced during the. next outage of sufficient duration or not later than October 30, 1992.

ADDITIONAL INFORMATZON These switches have previously 'been analyzed for failures in a 4kv circuit breaker application. That analysis concluded that 2000 cycles of the switch is a conservative estimate as to when the switch would need replacements The switches in the QR50 and QR 51 application have had approximately 1000 cycles during their life.

Licensee Event Report 250-89-011 was written because of an inadvertent safety injection initiation signal.

The switch manufacturer is General Electric Corporations The switch block model style number is CR2940.

This event was considered reportable in accordance with 10 CFR 50.73 (a) (2) (iv) .

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