ML18022A661

LER 88-013-00:on 880603,emergency Bus 1A-SA Deenergized Resulting in Automatic Start of Emergency Diesel Generator 1A-SA.Cause Undetermined.Failure of Battery Room Ventilation Damper Traced to Sticking Limit switch.W/880705 Ltr

ML18022A661
Person / Time
Site:	Harris
Issue date:	07/05/1988
From:	Jerrica Johnson, Watson R CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
HO-880135-(O), LER-88-013-02, LER-88-13-2, NUDOCS 8807130082
Download: ML18022A661 (6)

Text

AC CE1ZRATED DIS1'RIBUT10N DEMONSTR4 ON Sy~gg REGULRTOiINFORMATION DISTRIBUTION TEN (RIDE)

ACCESSION NBR:8807130082 DOC.DATE: 88/07/05 NOTARIZED: NO DOCKET ¹ FACZL:50-400 Shearon Harris Nuclear Power Plant, Unit 1, Carolina 05000400 AUTH. NAME AUTHOR AFFILIATION JOHNSON,J,R. Carolina Power & Light Co.

WATSON,R.A. Carolina Power & Light Co.

RECIP.NAME - RECIPIENT AFFILIATION

SUBJECT:

LER 88-013-00:on 880603,emergency diesel, start due to undervoltage on 1A-SA emergency bus.

W/8 ltr.

DISTRIBUTION CODE: ZE22D COPIES RECEIVED:LTR I ENCL TITLE: 50.73 Licensee Event Report (LER), Incident Rpt, etc.

/ SIZE:

NOTES:Application for permit renewal filed. 05000400 RECIPIENT COPIES RECIPIENT COPIES A" ZD CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-1 LA 1 1 PD2-1 PD 1 1 BUCKLEYFB 1 1 INTERNAL: ACRS MICHELSON 1 1 ACRS MOEZLER 2 2 AEOD/DOA 1 1 AEOD/DSP/NAS 1 1 AEOD/DSP/ROAB 2 2 AEOD/DSP/TPAB 1 1 ARM/DCTS/DAB 1 1 DEDRO 1 1 NRR/DEST/ADS 7E 1 0 NRR/DEST/CEB 8H 1 1 NRR/DEST/ESB 8D 1 1 NRR/DEST/ICSB 7 1 1 NRR/DEST/MEB 9H 1 1 NRR/DEST/MTB 9H 1 1 NRR/DEST/PSB 8D 1 1 NRR/DEST/RSB 8E 1 1 NRR/DEST/SGB 8D 1 1 NRR/DLPQ/HFB 10 NRR/DLPQ/QAB NRR/DREP/RAB 10 10

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TOTAL NUMBER OF COPIES REQUIRED: LTTR 45 ENCL 44 4

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Carolina Power 8 Light Company HARRIS NUCLEAR PROJECT P.O. Box 165 New Hill, NC 27562 J UE....5; 1988 File Number.'SHF/10-13510C Letter Number'HO-880135 (0)

U.S. Nuclear Regulatory Commission ATTN: NRC Document Control Desk Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 DOCKET NO. 50-400 LICENSE NO. NPF-63 LICENSEE EVENT REPORT 88-013-00 Gentlemen:

In accordance with Title 10 to the Code of Federal Regulations, the enclosed Licensee Event Report is submitted. This report fulfills the requirement for a written report within thirty (30) days of a reportable occurrence and is in accordance with the format set forth in NUREG-1022, September 1983.

Very truly yours, R. A. Watson Vice President Harris Nuclear Project JRJ:acm Enclosure cc.'Dr. J. Nelson Grace (NRC - RII)

Mr. B. Buckley (NRR)

Mr. G. Maxwell (NRC SHNPP)

MEM/LER-88-013/1/OS1

(943)'ICENSEE NRC Form 300 EVENT REPORT (LER)

US. NUCLEAR REQULATORY COMMISSION APPROVED OMB NO. 31500104 EXPIRES: 0/31/SS FACILITY NAME (II DOCKET NUMBER (2) PAOE 3 S H IS NUCLEAR POW R P 0 5 0 0 0 1 OF TITLE Iil EMERGENCY DIESEL START DUE TO UNDERVOLTAGE ON 1A-SA EMERGENCY BUS EVKNT DATE (5) LER NUMBER (0) REPORT DATE (7l OTHER FACILITIES INVOLVED (Sl

') SEQUENTIAL REVISlON MONTH FACILITYNAMES C DOCKET NUMBER($)

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MONTH OAY YEAR YEAR NUMSER NUMSSR OAY YEAR 0 5 0 0 0 0 6 0 3 8 8 8 8 0 1 0 0 0 7 0 8 8 0 5 0 0 0 OPKRATINQ THIS REPORT IS SUBMITTED PURSUANT T 0 THE REQUIREMENTS OF 10 CFR ()I IChech one or more of the foRorffnf) (11)

MODE (0) 20402(b) 20405(cl 73.71(bl 50.73(a) (2) (ix)

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.o. 9...'Pr <<<<4 20405(a) II) (r) 50.734) (2)(ill) 50.73(a) (2)(xl LICENSEE CONTACT FOA THIS LER (12)

NAME TELEPHONE NUMBER JOSEPEI)R. JOHNSON AREA CODE

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'I SENIOR SPECIALIST - REGULATORY COMPLIANCE 91 936 2- 208 COMPLETE ONE LINK FOR EACH COMPONENT FAILURE OESCAIBEO IN THIS REPORT (13)

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ABSTRACT:

On June 3, 1988, while conducting a monthly Operational Surveillance Test (OST-1124) on the 1A-SA 6.9kV Emergency Bus- Undervoltage Trip Actuating Device, the lA-SA Emergency Bus was deenergized resulting in an automatic

<< I I start of Emergency Diesel Generator 1A-SA and the initiation of Emergency Load Sequencing. The diesel started and Loaded, and plant operation was not affected. During the emergency load sequencing, the 1A-SA Emergency Service Water (ESW) Pump did not start as required, and the Reactor Auxiliary Building

,I (RAB) Battery Room "A" ventilation recirculation damper (AC-D4SA-1) failed to

.I operate as required upon a control room ventilation isolation signals Immediate investigation has not revealed the cause for Loss of power .to the 1A-SA Emergency Bus or failure of the 1A-SA ESW Pump to start. The failure of ~

the RAB Battery Room ventilation damper was traced to a sticking limit switch in the hydraulic drive unit of the damper.

Investigation into the cause of the Emergency Bus deenergization and the failure of the ESW Pump to start is continuing.

8807i30082 880705 'r PDR S

ADQCII, 05000400 PNU Iij>

4 NRC Form 300 (94)3)

NRC Form 3EEA U.S. NUCLEAR REQULATORY COMMISSION (94)3)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMS NO. 3)50M)04 EXPIRES: 8/3) /58 FACILITYNAME Ill NUMSER )2) LER NUMSER (5) PACE I3)

YEA/I SEQUENTIAL REVISION SHEARON HARRIS NUCLEAR POWER PLANT NUMEER NUM ~ R UNIT DESCRIPTION'OCKET 1 o s o o o 4008 8 013 0 0 2 oF0 4 TEXT /l//I>>/4 <<>>I>> /4 /)e/krer5 Iree a I/4/4/>>/HRC Fo/rrr 38343/ ) )7)

On June 3, 1988, the plant was operating .in Mode 1 at 99/ power. The 1A-SA Emergency Service Mater (ESW) Pump was operating supplying flow to the 1A-SA Emergency Service Water Header. An Operational Surveillance Test, OST-1124, 6.9kV Emergency Bus Undervoltage Trip Actuating Device Operational Test, was in progress on the 1A-SA Emergency 'us (EIIS:EK). This is a monthly Operati'onal Surveillance Test which had been " conducted without incident approximately 20 times in the past.

At 0717 the operator proceeded to test the undervoltage device and depressed the "red" pushbutton PB-SA on cubicle 10 of Bus 1A-SA as required by Step 7.1.7 of OST-1124. The test button actuates the test relay (86T) in order to block undervoltage trips during the test and allows the undervoltage relay (86UV) to actuate without causing a bus trip. The operator observed that the plant response was normal and, as required by Step 7.1.10, released the "red" pushbutton. The operator observed that both rel.ays 86UV and 86T reset automatically as expected; however, at this point in time (0719) circuit breaker 105, which supplied power to the 1A-SA Emergency Bus, tripped on bus undervoltage. This resulted in an automatic start of Emergency Diesel Generator (EDG) lA-SA and the subsequent initiation of Emergency Load Sequencing.

The diesel started and loaded normally and plant operation was not affected.

Load sequencing proceeded as designed except that the lA-SA Emergency Service Mater Pump did not restart in load block 3 as required, therefore, the operator manually started the pump at 0720.

Loss of the 1A-SA Emergency Bus caused voltage fluctuations in the power supply to the Control Room Ventilation outside air intake radiation monitors, which resulted in spurious Containment and Control Room ventilation isolation signals'he Reactor Auxiliary Building (RAB) Battery Room "A" ventilation recirculation damper (AC-D4SA-1) failed to operate as required upon initiation of the Control Room isolation signal.

CAUSE:

An immediate investigation of the event did not reveal any obvious cause for the undervoltage trip on the 1A-SA Emergency Bus or the failure of the 1A-SA ESM Pump to start. Control fuses were checked and no deficiencies were found. Procedure steps were verified, and it was established that personnel properly'ollowed the procedure. The ERFIS data base and operating logs were reviewed for possible indications of abnormal conditions or events. No abnormal conditions were found. Since a direct cause for the bus loss was not apparent and no abnormal conditions could be found, normal. power was restored to the 1A-SA Emergency Bus at 1137., and the EDG was secured at 1139.

NRC POIIM SEER *U.S.OPO:1955 0 524 538/455 r)94)3)

NRC Form 358A US. NUCLEAR REOULATORY COMMISSION I84ISI LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVED OMS NO. 3I50&184 EXPIRES: 8/31/88 FACILITYNAME III DOCKET NUMBER ISI LER NUMBER ISI ~ AOE (3)

SHEARON HARRIS NUCLEAR POWER PLANT YEAR I~ SEQUENTIAL NUM SR PI", REVISION orrr'NUMEEII UNIT TEXT ///moro opoco/5 /qlr/rorL Um ///Fooo//II/IC lro/III33$ 43/ IITI 06000400 88 0 13 0 OF 0 4 CAUSE: (continued)

Since the ESW Pump did not automatically start, it was declared inoperable.

Investigation into possible load sequencer related causes for the failure to start did not reveal any probable cause. A generic trip free condition in which the circuit breaker trip coil remained energized through the indicating light circuits was experienced in the past. This problem was corrected during the startup test program by FCR-SI-70(R2) and coul.d not have been the cause because the breaker closed on the manual signal. A spec'al test procedure (EPT-110T) was prepared to checkout and exercise the automatic start features of the ESW Pump through the Emergency Load Sequencer. During the test, the pump .started properl.y on a manual signal, therefore, the failure to start automatically is probably related to the automatic start circuitry. Two successful automatic starts of the ESW Pump using the Emergency Load Sequencer circuitry were accomplished on June 3, 1988, and the 1A-SA ESW Pump was declared fully operational at 2030 on June 3, 1988.

The failure of the battery room ventilation damper was traced to a sticking limit switch in the hydraulic drive unit of the damper. This was lubricated and the damper was returned to service on June 3, 1988. A failure analysis request has been initiated since at least one simil.ar failure has occurred.

ANALYSIS OF EVENT:

The loss of the 1A-SA Emergency Bus due to an apparent spurious undervoltage signal is a challenge to an engineered safety feature and" is being further investigated in order to preclude unnecessary challenges to the safety system. The direct cause of the undervoltage trip has not been established.

The portion of OST-,1124 related to the 1B-SB Emergency Bus was successful.ly conducted on the 1B-SB Bur at 1305 on June 6, 1988, three days after the undervoltage trip on the 1A-SA Emergency Bus. The'cause of the bus trip is probably related to the operation of rel.ays 86T and 86UV. These relays are eight stack rotary relays which consists of 8 independent switch wafers on a common operating shaft. During the reset process, circuit design requires that relay 86UV operate before 86T (86UV resets before the trip circuit is "unblocked" by the actuation of'6T). Wafer 1 of each relay controls the trip and reset process, and wafer 7 of each relay controls the bus supply breaker and undervoltage trip functions'or all practical purposes, resetting relay 86UV instantaneously resets relay 86T. Pl.ay or "slop" in the relay could allow the operation of wafer 7 to lag the operation of wafer 1 and result in improper sequencing of relay contacts. This condition has been observed in similar relays and could account for the bus trip. A special test will be developed and conducted to confirm or deny this relay condition.

NRC FORM 545A *U,S.GPO:1888&824 538/455 I883I

NRC FSIm 3SSA NUCLEAR REOULATOSY COMMISSION (84)3)

LICENSEE EVENT REPORT ILER) TEXT CONTINUATION'A- APPROVEOOI4IO NO 3180M)04 EXPIRES: 8/31/88 FACILITYNAME (I I OOCKET NUMSER (3) LER NUMSER (8) PACE (3)

SEOVENTIAL REVISION SHEARON HARRIS NUCLEAR POWER PLANT YEAR NVM ER NVMSEII UNIT 1 o s o o o4 008 013 0 QF0 4 TEXT //F Imvs EPEEP /I /EEv/RRE NIP afcWanel ///IC FomI 3(5A3) (IT)

ANALYSIS OF EVENT: (continued)

The failure of the 1A-SA ESW Pump to start under a val.id safety signaI is a safety concern. Although EPT-110T successfully demonstrated the oroper functioning of the pump to start from a safety signal on two occasions, further investigation is intended in an attempt to establish a more definitive root cause. Additional testing will be conducted in a manner that dupI.icates the conditions of this event to the maximum extent practicable inct.uding de-energizing the emergency bus. This test will be performed just prior to the July 1988 refueling outage.

This event was reportable in accordance with 10CFR50.73(a)(2)(iv) due to the actuation of an Engineered Safety Feature. There were no safety consequences as a result of this event. Plant operators took appropriate actions in accordance with AOP-025, "Loss of One Emergency AC Bus (6.9kV) or One Emergency DC (125V) Bus." This procedure requires operators to ensure specific equipment is operating after losing an Emergency Bus. The operator quickly noticed that 1A-SA ESW Pump had failed to restart and manuall.y started the pump. Without operator action, the 1A-SA Diesel wculd have eventually failed without cooling water from the 1A-SA Emergency Service Water Header.

This would not have created a significant safety consequence to the reactor since the plant is designed to withstand a single failure of one Emergency Bus. The 1B-SB Diesel and 1B-SB Emergency Bus were still available for operation.

There have been no similar events.

CORRECTIVE ACTIONS:

1. Investigation into the cause of the 1A-SA Emergency Bus undervoltage trip is continuing. Tests will be prepared and conducted as necessary to establish the root cause of the undervoltage trip and accomplish appropriate corrective action.

2. Investigation into the cause of the failure of the 1A-SA ESW Pump to start is continuing. Tests will be prepared and conducted as necessary to establish the root cause of the failure and accomplish appropriate corrective actions.

3. The RAB Battery Room "A" recirculation damper AC"D4SA-1 was repaired on June 3, 1988, and because a previous failure had been identified, a detailed failure analysis will be conducted.

NIIC SORM SESA RU.S GPO:1888.0-024 838/ESS (883)