ML17285A888

LER 89-010-01:on 890501,power Lost to Reactor Protection Sys 120-volt Instrument Bus a Twice,Causing ESF Actuations. Caused by Metal Nameplate Falling Into Power Supply Circuitry.Nameplates Removed from panels.W/891205 Ltr

ML17285A888
Person / Time
Site:	Columbia
Issue date:	12/05/1989
From:	Davison W, Powers C WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-010, LER-89-10, NUDOCS 8912150076
Download: ML17285A888 (6)

Text

ACCELERATED DISTMBUTION *DEMONSHRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8912150076 DOC.DATE: 89/12/05 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION DAVIDSON,W.S. Washington Public Power Supply System POWERS,C.M. Washington Public Power Supply System RECIP.NAME RECIPIENT. AFFILIATION

SUBJECT:

LER 89-010-01:on 890501,partial NSSSS actuation due to loss of power to RPS Bus A caused by equipment design deficiency.

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DISTRIBUTION CODE: IE22T 'COPIES RECEIVED:LTR i ENCL i 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 PD5 LA 1 1 PD5 PD 1 1 SAMWORTH,R 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 ACRS WYLIE 1 1 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 DEDRO 1 1 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB9H3 1 1 NRR/DET/ESGB 8D 1 1 NRR/DLPQ/LHFB11 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB11 1 1 NRR/DREP/PRPBll 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB 7E 1 1 NRR/DST/SPLBSDl NUDOCS-ABSTRACT RES/DSIR/EIB 1

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PLEASE HELP US TO REDUCE WASTEI CONTACI'HE.DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISlS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 38 ENCL 38

ti WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 Docket No. 50-397 December 5, 1989 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

NUCLEAR PLANT NO. 2 LICENSEE EVENT REPORT NO.89-010, Rev. 1

Dear Sir:

Transmitted herewith is Licensee Event Report No. 89-010-01 for the WNP-2 Plant. This report is submitted in response to the report requirements of 10CFR50.73 and discusses the items of reportability, corrective action taken, and action taken to preclude recurrence.

Very truly yours, C'k 4~~

C.H. Powers (M/D 927M)

WNP-2 Plant Manager CHP: lg

Enclosure:

Licensee Event Report No.89-010, Rev. 1 cc: Hr. John B. Hartin, NRC Region V Hr. C.J. Bosted, NRC Site (H/D 901A)

INPO Records Center Atlanta, GA Hs. Dottie Sherman, ANI Mr. D.L. Williams, BPA (H/D 399) rqg2g5007< Serf,20'g PDR Aooch, 05000%5'7 8 PDC

NRC FORM 366 V.S. NUCLEAR REGULA'TORY COMMISSION (64)9) APPROVED OMB NO. 31504)104 EXPIRES: 4/30/92 ESTIMATFD BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST'0,0 HRS, FORWARD LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPOATS MANAGEMENT BRANCH (P630). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104), OFFICE OF MANAGEMENTAND BUDGET. WASHINGTON. OC 20503.

FACILITY NAME (I) DOCKET NUMBER (2) PAGE 3i Washington Nuclear Plant - Unit 2 0 5 0 0 03 7>OF05 ar >a uc ear earn upp y u o ys em c ua >on ue o oss o ower o Reactor Protective System Bus HAH - Cause - Equipment Design Deficiency EVENT DATE (5) LFR NUMBER (6) AEPOAT DATE (7) OTHER FACILI'TIES INVOLVED (8)

MONTH OAY YEAR YEAR .gD) SEQUENTIAL NUMBER REVEI MONTH DAY YEAR FACILITYNAMES DOCKET NUMBER(5)

NUMBER 0 5 0 0 0 0 501 8 9 8 9 1 0 01 12 5 8 9 0 5 0 0 0 OPERATING THIS REPORT IS SUBMITTED PUASUANT 7 0 THE RLQUIAEMENTS OF 10 CF R (I: IChrck onr or morr ol the Iotrowinp/ (11 MODE (9) 20.402(B) 20.405(c) 60.73( ~ ) (2) (ivl 73.71(B)

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LICENSEE CONTACT FOR THIS LER (12)

NAME TELFPHONE NUMBER AREA CODE W.S. Davison, Compliance Engineer 509 37 7-2 501 COMPLFTE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) XT. 26 MANUFAC- COMPONENT MANUFAC.

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SUPPLEMENTAL REPOAT EXPECTED (14) MONTH OAY YEAR EXPECTED SUBMISSION DATE RSI YES Ilf yes, complrtr EXPECTED SVBhtISSIOH DATE/ NO ABSTRACT ILlmlt to f400 sprees, I r., rpproslmrtrly //Arm slnple spree ryprwrittrn linn/ 118)

During shutdown conditions for the annual refueling outage, power was lost to the HAH Reactor Protective System (RPS) 120 volt instrument bus on two occasions, causing ESF actuations in the form of primary and secondary containment isolations. The first occur-rence was May 1, 1989, at 2146 hours0.0248 days <br />0.596 hours <br />0.00355 weeks <br />8.16553e-4 months <br /> and the second occurrence was tray 3, 1989, at 1528 hours0.0177 days <br />0.424 hours <br />0.00253 weeks <br />5.81404e-4 months <br />. The first event was characterized by a momentary (less than 100 milli-second) loss of 120 volt AC power to the bus with attendant actuation of Primary Containment iso-lation groups 2,5,6, and 7. The second event differed in that the bus suffered a sus-tained loss of 120 volt AC power which caused not only a group 2,5,6, and 7 Primary Containment but a Secondary Containment isolation as well.

The cause of the event was a metal nameplate falling into the RPS bus UAH power supply circuitry resulting in a short circuit to ground. The short circuit caused power supply transients. Corrective actions consisted of: Prompt action by the plant operators to return the Residual Heat Removal Shutdown Cooling System to operation to restore cooling to the reactor and the recovery of other systems as needed in accordance with plant pro-cedures. Troubleshooting was implemented to discover the cause of the power loss. All nameplates were removed from the UAH side RPS power supply panels. The nameplates on the HBR side RPS power supply panel will be removed during the 1990 Refueling Outage.

NRC Form 388 (64)9)

NRC FORM 366A US. NUCLEAR REGULATOAYCOMMISSION (64)9) APPROVED OMB NO.31500104 EXPIRES: 4/30/92 ESTIMAT 0 BUADEN PER RESPONSE TO COMPI.Y WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION AEOUESTI 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P4)30), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 11IE PAPERWORK AEDUCTION PROJECT (31500104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON. DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LE A NUMBER (6) PAGE (3)

'j: SEDUENTIAL REVISION NUMBER 3'.':

NUMSS R Washin ton Nuclear TEXT Illmoro Plant - Unit

/1 roorr/rrd, IIJO oddio'ono/HRC 2 05'000397 8 9 0 1 0 0 1 2 OF 0 5 4poCO  %%dnn 35649/ (17)

Since all ESF systems responded as designed, these two events had no safety significance. This event presented no safety hazard to the public or Plant personnel.

Plant Conditions a) Power Level - OX b) Plant Mode - 4 (Cold Shutdown)

Event Descri tion During the annual refueling outage, on May 1, 1989, at 2146 hours0.0248 days <br />0.596 hours <br />0.00355 weeks <br />8.16553e-4 months <br />, while performing the Reactor Protective System ( RPS) Logic System Functional Test, the UAH RPS 120 volt AC power supply bus experienced an unexplained momentary loss of electrical power. As a result of this electrical transient which lasted less than 100 milli-seconds, Primary Containment Isolation groups 2,5,6, and 7 received a spurious ESF actuation signal causing the closure of the following valves:

RHR-V-53A (Shutdown Cooling Loop HAH Return Valve), RHR-V-53B (Shutdown Cooling Loop RBH Return Valve), RHR-V-8 (Shutdown Cooling Loop UAU Suction Containment Isolation Valve), RHR-V-23 (Shutdown Cooling Head Spray Valve), RHR-V-40 (Loop "BA Outboard Isolation to Radwaste), RHR-V-75A (Loop UAH Outboard Sample Isolation Valve), RHR-.V-75B (Loop HBH Outboard Sample Isolation Valve), MS-V-67D (Main Steam Isolation Valve MS-V-28D body drain isolation to the Main Condenser) EAll other body drain isolation valves were closed as a result of the shutdown.], EDR-V-20 (Drywell Equipment Drains Containment Isolation Outboard Valve), FDR-V-4 (Drywell Floor Drain Containment Isolation Outboard Valve), and RWCU-V-4 (Reactor Water Cleanup System Outboard Suction Isolation Valve).

Also, one half of the RPS trip logic was actuated, causing operation of half of the scram pilot solenoid valves (a half scram on the UA" side), and one half of the Main Steam Isolation Valve (MSIV) isolation logic (a half MSIV isolation) was actuated. Neither the half scram nor the half MSIV isolation resulted in actual equipment operation as these are circuit logic conditions only.

On May 3, 1989, at 1528 hours0.0177 days <br />0.424 hours <br />0.00253 weeks <br />5.81404e-4 months <br />, a second similar loss of power to the HAH RPS bus occurred. The difference between this event and the previous occurrence on May 1, 1989, was the fact that the Electrical Protection Assemblies (EPAs), located on the output side of the HAH RPS Motor Generator Set,,did actuate to deenergize the 120 volt HAH RPS bus. This resulted in a sustained loss of power to the bus causing spurious initiation of a Reactor Building Exhaust Plenum High Radiation signal (AZU signal) and the subsequent initiation of a Secondary Containment Isolation signal in addition to the ESF actuations caused by the previous event.

As a result of the spurious HZH signal the following actions occurred:

o Auto start of both Standby Gas Treatment trains.

NAC Form 366A (64)9)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 31500104 (6/9) ~

EXPIRES: 4/30)92 ESTIMABLE% BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT PORT (LER) INFORMATION COLLECTION REOUESTr 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P4)30), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1HE PAPERWORK REDUCTION PROJECT (31504)104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (11 DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SEOVENTIAL gj)r'6VISION NVM66R PB NUMBER Washin ton Nuclear Plant - Unit 2 o s o o o 397 89 01 0 01 0 4OF0 TEXT IIInroro spsco Js rsr)rrr)sd, rr>> sdditior>>l NRC %%drrn 3664's I (17)

4. The cause of the event was discovered to be Equipment Failure - Design Deficiency - Problem Not Anticipated:

As a result of troubleshooting efforts, a metal nameplate was found in the bottom of the RPS RA" power panel. The nameplate showed signs of arc damage. Investigation indicates that the nameplate had been lodged between the upper pole piece of the RPS "AH logic feeder circuit breaker and the power panel inner metal cover causing the RPS power supply to short circuit to ground. It was concluded that the direct short to ground caused bus voltage to drop enough to result in the observed power supply transients.

It was further concluded that the glue which attached the nameplate to the upper section of the power panel was degraded by heat in a manner unanticipated by the designer. The degradation of the glue allowed the nameplate to fall off into the circuit breaker area and cause the short to ground.

B. Corrective Action

l. A troubleshooting plan was written and implemented to discover the cause of the unexplained losses of the HA" RPS bus power supply.

2. The nameplates were removed from the UA" RPS power supply panel.

3. The nameplates on the "B" side RPS power supply panel will be removed during the 1990 Refueling Outage.

Safet Si nificance Since all of the ESF systems responded as designed to the spurious actuation signals, these two events had no safety significance. The loss of RHR Shutdown Cooling was responded to in a correct and timely fashion to return cooling and circulation to the reactor core within the Technical Specification time limits.

Had these events occurred with the plant operating at power, some of the systems would have been subjected to thermal, flow and pressure transients of greater magnitude. This type of local system transient is within the scope of the design of the various systems and would have presented no safety concern. This event presented no safety hazard to the public or Plant personnel.

Similar Events Two previous similar events have occurred at WNP-2. LER 85-025-01 "Engineered Safety Feature Isolations and Actuations Caused by Reactor Protection System Equipment Failure" documented a loss of the UA" RPS bus which was attributed to failure of the EPA circuit breaker RPS-EPA-3A undervoltage relay coil. LER 86-011-00 "Nuclear Steam Supply Shutoff System Actuation due to !momentary Loss of Instrument Power" documented a momentary loss of power to the HBH RPS bus. The cause of this event was not able to be determined.

NRC Form 366A (669)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPAOVED OMB NO. 3'1500104 (6 f9% ~

EXPIRES: 4/30/92 ESTIMATE BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE AECOADS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (F4130), U.S. NUCLEAR R EGULATOAY COMMISSION, WASHINGTON, OC 20555, AND TO

%HE PAPERWORK REDUCTION PROJECT (31504)1041, OFFICE OF MANAGEMENTAND BUDGET. WASHINGTON, DC 20503.

FACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3),

VEAA g SEQUENTIAL NUMSER REVISION

')v+ NUMSER Washin ton Nuclear Plant - Unit 2 0 5 0 0 0 9 7 8 9 OF TEXT /lfmore eoeoe /4 eoII/red, Iree eddrrlone/NRC Form 3664'4/ (IT)

EI IS Information Text Reference EI IS Reference System Component RPS JC JC HAR RPS Motor Generator Set JC 88 RHR-V-53A BO V RHR-V-53B BO V RHR-V-40 BO V RHR-V-75A BO V RHR-V-758 BO V MS-V-67D SB V MS-V-28B SB V EDR-V-20 WH V FDR-V-4 WH V MSI V SB V Standby Gas Treatment BH Technical Support Center HVAC VK'A Reactor Building Emergency Room Coolers HX Reactor Building Equipment and Floor Drain Sump Pump Header WH PSF Secondary Containment Ventilation System VA Reactor Building Supply and Exhaust Fans VA RHR Shutdown Cooling BO RWCU-V-4 CE V HAH RPS Power Supply Panel JC RJX HBH RPS Power Supply Panel JC RJX N RC Form 366A (639)