ML17292B742

LER 99-001-00:on 990628,ESF Signal Closed All Eight MSIVs While Plant Was Shutdown.Caused by Failure of Relay RPS-RLY-K10D.Subject Relay Was Replaced & Tested on 990630. with 990720 Ltr

ML17292B742
Person / Time
Site:	Columbia
Issue date:	07/20/1999
From:	Sherman R, Galen Smith WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-99-135, LER-99-001, NUDOCS 9907270226
Download: ML17292B742 (8)

Text

CATEGORY0 REGULATORY INFORMATION DISTRIBUTION SYSTEM (RZDS)

ACCESSION NBR:9907270226 DOC.DATE: 99/07/20 NOTARIZED: NO DOCKET FACZL:50'-397 WPPSS Nuclear Project, Unit 2, Washington Public POwe 05000397 AUTH.NAME AUTHOR AFFILIATION, SHERMAN,R.N. Washington Public Power Supply System SMITH,G.O. Washington Public Power Supply System RECZP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 99-001-00:on 990628,ESF signal closed all eight MSZVs while plant was shutdown. Caused by failure of relay RPS-RLY-K10D.Subject relay was replaced & tested on 990630.

With 990720 ltr.

DISTRIBUTION CODE: XE22T COPIES RECEIVED:LTR ENCL SIZE:

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

RECIPIENT COPIES RECXPIENT COPIES 0 ZD CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL LPD4-2 PD 1 1 CUSHING, J 1 1 R XNTERNALs ACRS 1 1 LE C E 1 1 NRR/DIPM/ZOLB 1 1 NRR7DRZ P /REXB RES/DET/ERAB 1.

1

' 1 NRR/DSSA/SPLB 1 1 RES/DRAA/OERAB 1- 1 RGN4 FXLE 01 1 1 EXTERNAL: L ST LOBBY WARD 1 1 LMXTCO MARSHALL 1 1 NOAC POORE,W. 1 1 NOAC QUEENER,DS 1 '1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 D 0

M NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE TO HAVE YOUR NAME OR ORGANIZATION REMOVED FROM DISTRIBUTION LISTS

~

OR REDUCE THE NUMBER OF COPIES RECEIVED BY YOU OR YOUR ORGANIZATION, CONTACT THE DOCUMENT CONTROL DESK (DCD) ON EXTENSION 415-2083 FULL TEXT'CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUXRED: LTTR 16 ENCL 16

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WASHINGTON PUBLIC POWER SUPPLY SYSTEM PO. Box 968 ~ Richlanrl, Washington 99352-0968 July 20, 1999 G02-99-135 Docket No. 50-397 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 Gentlemen:

Subject:

%NP-2, OPERATING LICENSE NPF-21 LICENSEE EVENT REPORT NO. 99-001-00 Transmitted herewith is Licensee Event Report No. 99-001-00 for WNP-2. This report is submitted pursuant to 10 CFR 50.73 and discusses the items of reportability, corrective action taken, and action to preclude recurrence.

Should you have any questions or desire additional information pertaining to this report,.please call me or PJ Inserra at (509) 377-4147.

Respectfully, 0 Smith Vice President, Generation Mail Drop 927M Attachment cc: EW Merschoff - NRC MV NRC Senior Resident Inspector - 927N (2)

JS Cushing - NRC NRR DL Williams - BPA/1399 INPO Records Center PD Robinson - Winston K Strawn 9907270226 990720 PDR ADQCK 05000397 S PDR

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

WNP- 2 50-397 10F 4 TITLE (4)

Failed Relay Causes ESF Signal to Close All 8 MSXV's While Plant Was Shutdown EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHFR FACILITIES INVOLVED (8)

MONTH DAY SEQUENTTAL REV. YEAR FACIUTYNAME NUMBER 001 00 07 20 1999 FATTY NAME 06 28 99 1999 OPERATING HODE THIS REPORT IS SUBHITTED PURSUANT TO THE REQUIREMENTS OF 10 CPR 5: (Check one or sore) (11) 20A02(b) 20AOS(c) x 50.73(a)(2)(iy) 73.71(b)

POWER LEVEL 20AOSa 1 5036 c 1 50.73 a v 73.71 c 20A05(a)(1) 00 50.36(c)(2) 50.73(a)(2)(vll) OTHER

20. s 1 6 50. s I A

20. a 1 50.73 a 50. a I

20. a 1 50.73 a i 50.73 a LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER (Irc)ude Area Code)

R.N. Sherman, Licensing Engineer (509) 377%616 COMPLETE ONE LINE FOR EACH CCMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE COMPONENT MAMJFAcnATER REPORTABLE kg/i '"' CAUSE MANUFACTURER REPORTABLE TO EPIX TO EPIX g:;P~g X JC RLY G080 NO SUPPLEMENTAL REPORT EXPECTED (14 ) EXPECTED YES NO X

(@yea, comp(eted EXPECTED SUNOSSION DATE).

On June 28, 1999 at approximately 1244 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.73342e-4 months <br /> the plant was in Mode 4 during a fuel savings dispatch. The reactor vessel head was in place and the head bolts properly tensioned. All control rods were verified to be full in and no core alterations were in progress. The A-Train of the Residual Heat Removal System was in service and performing the shutdown cooling function. The Emergency Core Cooling System equipment that is required by technical specifications for Mode 4 operation was operable. A surveillance of the main turbine throttle valve position switches was in progress. The Nuclear Steam Supply Shutoff System (NSSSS) generated an unexpected Main Steam Isolation Valve (MSIV) closure signal, and all eight MSIV's and the inboard main steam line drain valve closed. Surveillance testing of the main turbine throttle valve position switches was stopped. An Incident Review Board was formed to investigate the event. The resident NRC inspector was notified and the NRC was notified of the unexpected Engineered Safety Feature (ESF) actuation via the Emergency Notification System. The cause of this event was the failure of Reactor Protection System relay RPS-RLY-K10D, in that contacts opened due to vibration from an adjacent relay under test. This generated a half MSIV closure signal. The other half isolation signal was generated, as expected, by the main turbine throttle valve position switch surveillance. There were no personnel errors or procedural deficiencies that contributed to this event. Relay, RPS-RLY-K10D, was replaced and tested on June 30, 1999. In addition, testing of the turbine throttle valves was completed on July 1, 1999, and did not cause an MSIV closure signal. There were no safety consequences associated with this event. This event is being reported per the requirement of 10CFR50.73(a)(2)(iv) as an event or condition that resulted in an automatic actuation of an Engineered Safety Feature. The ESF automatic actuation was not from a valid NSSSS actuation signal. However, the actuation occurred while the isolation s stem was in service.

LICENSEE EVENT REPORT (LER)

Failed Rela Causes E$ F Si to Close All 8 MSIV's While Plant Was Shutdown fACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER {6) PAGE { 3)

SEQUENTIAL REVISION NUMBER NUNB6R WNP-2 50-397 99 001 00 2 OF 4 TEXT (If more space is required, Use addNonal copies of NRC Form 366A) (17j Event Descri tion On June 28, 1999 at approximately 1244 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.73342e-4 months <br /> the plant was in Mode 4 during a fuel savings dispatch. The reactor vessel head was in place and the head bolts properly tensioned. All control rods were verified to be full in and no core alteiations were in progress. The A-Train of the Residual Heat Removal (RHR) System was in service and performing the shutdown cooling function. The Emergency Core Cooling System (ECCS) equipment that is required by technical specifications for Mode 4 operation was operable. A surveillance of the main turbine throttle valve position switches was in progress. The Nuclear Steam Supply Shutoff System (NSSSS) generated an unexpected Main Steam Isolation Valve (MSIV) [SB, ISV]

closure signal, and all eight MSIV's and the inboard main steam line drain valve closed.

The resident NRC inspector was notified and the NRC Operations Center was notified of the unexpected Engineered Safety Feature (ESF) actuation via the Emergency Notification System (ENS). &e notification Event Number is 35877. The ENS notification cited 10CFR50.72(b)(2)(ii), ESF actuation.

Immediate Corrective Action Surveillance testing of the main turbine throttle valve position switches was stopped. An Incident Review Board (IRB) was formed and the event was investigated.

Further Evaluation The IRB determined that during the surveillance test of the 04 Turbine Throttle Valve, the valve position relay, RPS-RLY-K10H [JC, RLYj was energized as a result of the II4 Turbine 'Ilmottle Valve being opened. This condition was expected and provides one-half of the NSSSS logic needed to generate a signal for closure of the MSIV's. In addition, the IRB determined the contacts of the valve position relay for the 83 Turbine Throttle Valve, RPS-RLY-K10D [JC, RLY], opened due to vibration from the operation of relay RPS-RLY-K10H. This was not anticipated and provided one-half of the NSSSS logic needed to generate a signal for closure of the MSIV's. The two NSSSS channel signals, together, were sufficient to generate the MSIV closure signal, which caused the eight MSIV's and the inboard main steam line drain valve to close. The bvo relays involved in this event, RPS-RLY-K10H and RPS-RLY-K10D are physically adjacent to one another.

This event is being reported per the requirement of 10CFR50.73(a)(2)(iv) as an event or condition that resulted in an automatic actuation of an Engineered Safety Feature. The ESF automatic actuation was not from a valid NSSSS actuation signal. However, the actuation occurred while the isolation system was in service.

0 LICENSEE EVENT REPORT (LER)

Failed Rela Causes ESF Si to Close All 8 MSIV's While Plant Was Shutdown FACILITY NAME II ) DocKET NUMBER I E) LER NUMBER Is) PAGE I 3)

SEQUENTIAL asvrsroN NUMBER NUNBER WNP-2 5 0- 3 97 99 001 00 3 OF 4 TEXT (If more space Is required, use addit)or)al copies of NRC Form 366A) (1 T)

The following information regarding this event is provided to enhance the Significance Determination Process:

I. Both trains of Emergency AC power were operable and capable of performing their intended safety function.

2. The High Pressure Core Spray System was operable and capable of performing its intended safety function.

3. The A Train of the Residual Heat Removal System was in service performing the Shutdown Cooling function and the B train was operable and capable of performing its intended safety function.

Allcontrol rods were verified full in and no core alterations were in progress.

The event described above did not involve a loss of intended safety function. In addition, the event described above did not involve an event or condition that alone could have prevented the fulfillment of any safety functions described in 10CFR50.73(a)(2)(v).

Root Cause The cause of this event was the failure of relay RPS-RLY-KIOD, in that contacts opened due to vibration &om an adjacent relay under test. This generated an MSIV closure signal. This conclusion is supported by physical evidence obtained by plant test equipment. There were no personnel errors or procedural deficiencies that contributed to this event.

The investigation regarding the cause of the relay to fail when it was subject to vibration is ongoing. The prelinunary examination did not identify evidence of materials degradation that could have contributed to intermittent opening of contacts 11-12. Metallic and non-metallic parts appear to be in good condition. The momentary opening of the contact is believed to be the result of insufficient contact wipe, which made the 11-12 contact shock sensitive in the dewnergized state.

The calibration sheet for the relay, dated February 9, 1994, has been reviewed and indicates the wipe and gap settings were acceptable. A test of the relay indicates the normally closed wipe for the 11-12 and the 9-10 contacts is unacceptable. At this time there is no explanation for the reduction in contact wipe from the 1994 information. Additional examiiiation of the fingers and spring force measurements are underway.

Further Corrective Action Relay, RPS-RLY-KIOD, was replaced and tested on June 30, 1999. In addition, testing of the turbine throttle valves was competed on July 1, 1999, and did not cause an MS1V isolation signal to be generated.

Assessment of Safe Cons uences There were no safety consequences associated with this event. The closure of the MSIV's while in Mode 4, did not impact plant safety because reactor coolant system temperature was limited to less than 200'. The control rods were fully inserted at the time of the MSIV closure. The Emergency Core Cooling Systems that are required by tcchnical specifications were operable and capable of performing their intended safety functions. The A-Train of the RHR system was operating and performing the shutdown cooling function. This event did not represent a threat to the health and safety of the public or plant personnel.

LICENSEE EVENT REPORT (LER)

Failed Rela Causes FSF Si to Close All 8 MSIV's While Plant Was Shutdown FACILITY HAHE ( I) DOCKET HVHBER (2) LER HUHBER (6) PAGE I 3)

SEQUENTIAL RINISION NUHBER NUNS SE WNP-2 50-397 99 001 00 4 oF 4 TEXT (lf more space is required, use addiUonal copies of NRC Form 366A) (17)

Similar Events No previous similar events were identi6ed where all eight MSIV's were closed due to failed relay.