05000029/LER-1986-004, Forwards LER 86-004-00 Re Reactor Scram Due to Loss of Heater Drain Pumps During Severe Lightning Storm

Forwards LER 86-004-00 Re Reactor Scram Due to Loss of Heater Drain Pumps During Severe Lightning Storm

ML20212B358
Person / Time
Site:	Yankee Rowe
Issue date:	07/01/1986
From:	St Laurent N YANKEE ATOMIC ELECTRIC CO.
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 8608060305
Download: ML20212B358 (1)

LER-2086-004, Forwards LER 86-004-00 Re Reactor Scram Due to Loss of Heater Drain Pumps During Severe Lightning Storm

Event date:
Report date:
0292086004R00 - NRC Website

text

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YANKEE ATOMIC ELECTRIC COMPANY r.i.o on.ca, n ara 2<.s2e, m.%

Jr- Star Route, Rowe, Massachusetts 01367

.YAuxes .

July 1, 1986 U.S. Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Attention: Dr. Thomas E. Murley, Regional Administrator

Subject:

Licensee Event Report 50-29/86-04 Reactor Scram - Loss of Heater Drain Pumps 0:::r Sir:

In accordance with 10 CFR 50.73(a)(2)(iv), the attached Licensee Event Report is hereby submitted.

Very truly yours, hM& b'1 Iku Normand N. St. Laurent Plant Superintendent RLB/nm Enclosure cc: [3] NSARC Chairman (YAEC)

[1] Institute of Nuclear Power Operations (INPO) 8608060305 e60701 )

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LICENSEE EVENT REPORT (LER)

DOCKET NUMSER (23 FAGE(3 FACILITY NAast (1)

Yankee Nuclear Power Station, Rowe, Massachusetts o ]s l 0 l0 l 0 ]0 l2 l9 1 lOFl012 TITLE 146 Reactor Scram - Loss of Heater Drain Pumps LER NUMSER 161 REPORT DATE (7) OTHER F ACILITIES INVOLVED 183 EVENT DATE (St e

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LICENSEE CONT ACT FOR TH18 LER (12)

TELEPMONE NUM0ER NAME ARE A COCE Lee Boutwell - Senior Plant Engineer 4 l i i3 4 g 2 i4li5 12 16 i l COMPLETE ONE LINE FOR EACM COMPONENT F AILURE DESCRISED IN THIS REPORT (13)

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While operating at 100% power in Mode 1 on June 1, 1986, a severe lightning storm caused a disturbance on the plant's 120 Volt A.C. M-G Set Distribution panel. The resulting voltage surge caused the failure of the Heater Drain Tank Level Control Channel, which tripped both Heater Drain Pumps. The loss of the Heater Drain Pumps tripped the three Boiler Feed Pumps on low suction pressure with a resulting loss of feedwater. Attempts to restart the pumps failed and the reactor scrammed at 2034 hours0.0235 days <br />0.565 hours <br />0.00336 weeks <br />7.73937e-4 months <br /> on low steam generator level.

All automatic safety systems functioned as required or were available for operation except for panalarms N-A34, N-A35, N-A36, N-A40, N-A41, N-A42, N-A46, N-A47, N-A48, T-C79, T-C80, and T-C90 through T-C102. The Heater Drain Tank Level Control Channel power supply was found damaged and was replaced.

There was no adverse affect on the health or safety of the public as a result of this event.

This is the first event of this nature. The plant was returned to power on June 3, 1986.

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NRC Feren'386A U.S. NUCLEAA KEIULATORY COMMIS$10N e.eenovEo oMe No aiso-olo4 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION EXP6.ES 8/31/B5 FACILITY NAME (1) DOCKET NUMBER (2) LER NUMSLR (6) PAGE (33 Yankee Nuclear Power Station "El' ' YE Rowa, Massachusetts oF 0 5jojol0l0l2l9 8]6 -

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0 l0 0l2 0 l2 TEXT (J more space is regured ese addboonst NRC Forrn J66NsJ I1M While operating at 100% power in Mode 1 on June 1, 1986, a severe lightning storm caused a disturbance on the plant's 120 Volt A.C. M-G Set Distribution panel. The resulting voltage surge caused the failure of the Heater Drain Tank Level Ccntrol Channel which tripped both Heater Drain Pumps. The loss of the Heater Drain Pumps tripped the three (3) Boiler Feed Pumps on low suction pressure with a resulting loss of feedwater. Attempts to manually restart the Boiler Feed Pumps failed, because the Heater Drain Pumps could not be restarted due to the failed Heater Drain Tank Level Controller.

Subsequently, the reactor scrammed at 2034 hours0.0235 days <br />0.565 hours <br />0.00336 weeks <br />7.73937e-4 months <br /> on low steam generator level due to the loss of feedwater. The No. 2 Emergency Diesel Generator .

automatically started and supplied the No. 2 480 volt Emergency Bus.

Following the reactor trip, a Boiler Feed Pump was restarted and feedwater was restored. The No. 2 480 Volt Emergency Bus was normalized and the No. 2 Diesel Generator was returned to its auto lineup. All automatic safety systems functioned as required or were available for operation except for panalarms N-A34, N-A35, N-A36, N-A40, N-A41, N-A42, NOA46, N-A47, N-A48, T-C79, T-C80, and T-C90 through T-C102.

The Heater Drain Tank Level Control Channel failed due to a damaged power supply (rectifier bridge) which was replac.ed. The Secondary Vent and Drain Systeii Healer Drain To.k Level Control Channel Power supply, FW-P/S-402, Model 2AX-PS9A is manufactured by Foxboro.

The voltage transients caused by the severe lightning storm also caused the failure of other plant equipment as follows. The No. 1 Vital Bus Inverter fuses blew causing the inverter to shift to bypass with no loss of loads. An investigation disclosed that no damage had occurred to the inverter. The fuses were replaced and the inverter was returned to normal. The panalarms power supply, alarm cards, and a flasher card failed causing a loss of Panalarms N-A25 to N-A48 and T-C73 to T-C120. The failed power supply and cards were replaced and the panalarms were returned to service. In addition, damage to certain security system concentrators occurred and was reported as Physical Security Event Report 86-2.

The cause of this event has been attributed to the severity of the lightning i storm which induced voltage spikes of sufficient magnitude to cause the Heater Drain Tank Level Control Channel power supply, FW-P/S-402, and the other identified equipment to fail.

The Loss of Feedwater event is bounded by the Transient Analysis. The Emergency Feedwater System was operable as assumed and would have provided the required feedwater if normal feedwater had not been restored. There was no adverse affect on the health or safety of the public as a result of this event.

This is the first event of this nature and is believed to be an isolated incident. A lightning induced electrical disturbance on the Z-126 115 KV transmission line was reported in LER 83-22. The plant was returned to power on June 3, 1986.

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