ML17291A647

LER 95-001-00:on 950113,failed to Satisfy Single Failure Criteria for Containment Isolation Function Due to Electrical Separation Plate in Control Panel Missing. Replaced Missing barrier.W/950207 Ltr

ML17291A647
Person / Time
Site:	Columbia
Issue date:	02/07/1995
From:	Hugo B, Parrish J WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-95-027, GO2-95-27, LER-95-001, LER-95-1, NUDOCS 9502150115
Download: ML17291A647 (5)

Text

PRIORITY ACCELERATED RIDS PROCESSI iG REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9502150115 DOC.DATE: 95/02/07 NOTARIZED- NO DOCKET g FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION HUGO,B.R. Washington Public Power Supply System PARRISH,J.V. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 95-001-00:on 950113,failed to satisfy single failure criteria for containment isolation function due to electrical separation plate in control panel missing.

Replaced misszng barrier.W/950207 ltr.

DISTRIBUTION CODE: IE22T 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 PD4-2 PD 1 1 CLIFFORD,J 1 1 INTERNAL: ACRS 1 1 AEOD/SP~-RAB 1 1 AEOD/SPD/RRAB 1 1 CFXXiE-CENTERD02 1 1 NRR/DE/ECGB '1 1 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DIS P/PIPB 1 1 NRR/DOPS/OECB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRSS/PRPB "'2 '2 NRR/DSSA/SPLB 1 1 NRR/DSSA/SRXB 1 1 RES/DSIR/EIB 1 1 RGN4 FILE 01 1 1 EXTERNAL L ST LOBBY WARD 1 1 LITCO BRYCE g J H 2 2 NOAC MURPHY,G.A 1 1 NOAC POORE,W. 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL"RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE iVASTE! CONTACI THE DOCI.'ilENTCONTROL DESK. ROOM P 1-37 (EXT. 504-2083 ) TO ELIMINATEYOUR NAME F ROD!

DISTRIBUTION LISTS FOR DOCI MENTS YOU DON"I'EED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 27 ENCL 27

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352-0968 ~ (509) 372-5000 February 7, 1995 G02-95-027 Docket No. 50-397 Document Control Desk U.S. Nuclear. Regulatory Commission Washington, D.C. 20555 Gentlemen:

Subject; NUCLEAR PLANT WNP-2, OPERATING LICENSE NPF-21, LICENSEE EVENT REPORT NO.95-001, REVISION 0 Transmitted herewith is Licensee Event Report No.95-001 for the WNP-2 Plant. 'This voluntary report is submitted due to potential NRC interest and discusses the items of reportability, corrective action taken, and action taken to preclude recurrence.

Should you have any questions or desire additional information, please call me or D.A. Swank at (509) 377-4563.

Sincerely,

. V. Parrish (Mail Drop 1023)

Vice-President, Nuclear Operations JVP/BRH Enclosure CC: LJ Callan, NRC-RIV KE Perkins, Jr., NRC-RIV, Walnut Creek Field Office NS Reynolds, Winston & Strawn NRC Sr. Resident Inspector (Mail Drop 927N, 2 Copies)

INPO Records Center - Atlanta, GA DL Williams, BPA (Mail Drop 399) 9502i50ii5 950207 PDR ADOCK 05000397 PDR

+ g8

n LICENSEE EVENT REPORT (LER)

FACE)TV NAME I'l DOCKET NUM<<EN (a PACE (S)

Washington Nuclear Plant Unit 2 0 5 0 0 0 3 9 7 1 o)'

TRLE(s) Inability to Satisfy Single Failure Criteria for Containment Isolation Function Due to Missing Electrical Separation Plate in Control Panel EVENT DATE (S) R(PORT DAIS (I) DTINR FAcs)TKs ervoLY(D (ro SEOUENRAL DOCKET IANISER(s)

FACERY NAMES NLRIs(R N/A 0 5 0 0 0 1 13. 95 95 0 0 0 0 02 07 95 0 5 0 0 0 op(RAT<<(Q TISS R(PORT IS SVdM()T(D PLNSUAN( TO THE REQUNEM(NTS OF 10 Crit (11)

MODE (0) 1 I 20402(b) ) 20.405c ) 60.73(s)(2)(iv) I I 73.71(b)

) 20.405(s)(1)(i) ) 50.36(c)(l) ) 60.73(s)(2)(v) ) 73.71(c)

POW(R LEVEL 20.405 (s) (1) (>>) ) S0.36(c)(2) ) 60.73(s)(2)(vi) ( X ( OTHER(Specify in Abet(oct below srxf IIO) in Text, NRC Form 366A) 20.405(s)(1)(M) ) 50.73(s](2)(i) ) 50.73(s)(2)(vi<<)A P P I Voluntary

) 20.405(s](l)(iv) ) 50.73(s)(2)(ii) ) 60.73(s)(2)(v>>i)B

"'<:Y"': 'b"'?'.'?i:"'.::: "::"',:~;".!.":Nil'! ) 20.405(s)(1)(v) ( 50.73(s)(2](iri) ) S0.73(s)(2)(x)

L)c(NSEE CONTACT FOR TMS LER (Ia TEL(PI)ONE NUMSER Bruce R. Hugo, Compliance Engineer 377-8593 509 COMPLETE ONE LPN Fon EAcH COMP(NNNT FAKURE D(scr>>sro IN T)ss REPoRT (Ia R(PORTASLE SYSTEM R(PORTA(LE TO IPROS TO )PADS S(NPLEMENTAL REPORT EXPECT(D ((S) EXPECTED MONTH YEAR SUBMISSION YES (if yss, complete EXPECTED SUBMISSION DATE) IX I NO DATE (16)

ASSTRACT (ld)

At 1215 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.623075e-4 months <br /> on December 19, 1994, with WNP-2 at 100% power, an engineering supervisor performing a control panel walkdown discovered a missing electrical separation barrier plate inside the control room Reactor Core 'or Isolation Cooling (RCIC) control panel. With the barrier missing a short fire in the panel could disable the isolation capability of the system. The loss of electrical separation was initially believed to be limited to two steam trap drain line valves. On January 13, 1995, further review revealed that other valves in the system were affected, including the redundant steam supply isolation valves.

The loss of the ability to isolate the RCIC system with an assumed single failure was initially evaluated as rendering the isolation function inoperable. This event was accordingly reported per 10 CFR 50.72. Further investigation, including a review of Generic Letter 91-18, revealed that the actual status of the isolation function was operable but degraded. This event is being reported voluntarily due to potential NRC interest.

Corrective actions included replacement of the missing barrier and a walkdown of other panels. No additional similar problems were found. The cause of the missing plate could not be determined. The event had negligible safety significance due to the low probability of a fault: in the affected panel area.

LICEN EVENT REPORT (LER) TEXT C NUATION YfAR <<<:

< KQVOITIAL Washington Nuclear Plant Unit 2 0 5 0 0 0 3 9 7 95 -00 1 0 0 2 oF 3 TEXT (17)

Event

Description:

At 1215 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.623075e-4 months <br /> on December 19, 1994, with WNP-2 in Operational Condition 1 (Pow'er Operation) at 1004 power, a Supply System engineering supervisor performing a control panel [CBD] walkdown discovered a missing electrical separation barrier plate inside the control room Reactor Core Isolation Cooling (RCIC) [BN] control panel. The barrier provides electrical separation between redundant division wiring for valve control and isolation logic for the RCIC system, RCIC High Energy Line Break (HELB) mitigation, and RCIC primary and secondary containment isolation functions [JM]. With the barrier missing a short or fire in the panel could disable the isolation capability of the system.

Although the missing plate was discovered on December 19, the loss of electrical separation was initially believed to be limited to two steam trap [TRP] drain [DRN] line valves [ISV]. On January 13, 1995, further review revealed that other valves [V] in the system were affected, including the redundant steam supply isolation valves.

Immediate Corrective Action:

Since the RCIC control panel is in the front of the continuously manned control room, credit for a continuous fire watch was taken.

A replacement barrier was fabricated and installed on December 22, 1994.

Further Evaluation:

The loss of the ability to isolate the RCIC system with an assumed single failure was initially evaluated as rendering the isolation function inoperable. This event was accordingly reported at 0847 hours0.0098 days <br />0.235 hours <br />0.0014 weeks <br />3.222835e-4 months <br /> on January 13, 1995, via the Emergency Notification System per 10 CFR 50.72 (b)(2)(iii) as "Any event or condition that alone could have prevented the fulfillment of the safety function of structures or systems that are needed to: (C) Control the release of radioactive material Further review of this issue, including a review of the guidance in Generic Letter 91-18, revealed that the actual status of the isolation function was operable but degraded. This event is being reported voluntarily due to potential NRC interest.

There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.

LICENS VENT REPORT (LER) TEXT COL UATION Washington Nuclear Plant Unit 2 05 0 0 0 3 9 7 95 001 0 0 TKCf (17)

Root Cause:

Maintenance records were reviewed to identify work that would'have required removal of the plate; however, no work meeting this criteria was found. Thus the root cause of this problem, which may have existed since initial plant operation, could not be determined.

Further Corrective Actions:

Other control room panels were examined to find similar problems.

No other missing electrical separation barriers were identified.

Safety Significance:

This event had negligible safety significance. Probabilistic Risk Assessment methods were used to estimate the probability of a single failure in the affected panel area disabling the isolation function during an accident. Although the actual distance between cables

[CBL] in the separate divisions was at least 3.5 inches, the cables were conservatively assumed to be in contact for the failure probability calculation. The estimated failure rate was 5 x 10(-7) failures per demand, equivalent to a negligible 5 percent increase in conditional containment failure probability.

Previous Similar Events:

LER 91-10 described wiring separation errors affecting the containment isolation valves for the reactor recirculation system

[AD]. flow control valve [FCV] hydraulic supply. Corrective actions included establishment of a fire tour and correction of the wiring error.

LER 92-31 described an electrical separation deficiency resulting from an inadequate design analysis for a design change. Corrective actions included establishment of a fire tour, a review of other circuits for similar problems, and correction of the separation deficiency.

LER 93-30 describes electrical separation discrepancies due to missing cable tray [TY] covers and other similar deficiencies.

Corrective actions included walkdowns of cable raceways [FA],

correction of deficiencies, and design configuration control program improvements.

These corrective actions would not be expected to have prevented the event described in this report.