05000344/LER-1981-025, Forwards LER 81-025/03L-0.Detailed Event Analysis Encl

Forwards LER 81-025/03L-0.Detailed Event Analysis Encl

ML20032D378
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	11/02/1981
From:	Yundt C PORTLAND GENERAL ELECTRIC CO.
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20032D379	List: 05000344/LER-1981-025, Forwards LER 81-025/03L-0.Detailed Event Analysis Encl 05000344/LER-1981-025-03, /03L-0:on 811104,power to Preferred Instrument Bus Y11 Lost for 1 Minute Due to Failure of Output Current Sensing Relay on Associated Static Inverter.Caused by Normal Relay end-of-life.Relay Replaced
References
CPY-851-81, NUDOCS 8111130716
Download: ML20032D378 (3)

LER-1981-025, Forwards LER 81-025/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3441981025R00 - NRC Website

text

.. _

s

• 4 M

M

&&~

)

'5W

/

g Portland General Electric Company

'El-0 13 D 54 Trojan Nuclear Plant P.O. Bcx 439 Rainier, Oregon 97048 liEGCllyl (503)S56-3713 November 2,1951 CPY-851-81 t-8 9

Mr. R. H. Engelken, Director US Nuclear Regulatory Commission kf EI Region V - Suite 210

--f NOV1219915 1450 Maria Lane i f u. DaTN,

I Walnut Creek, California 94596-5368 rA4

Dear Sir:

b j tu In accordance with the Trojan Plant Operating License, Appendix,,

US NRC Technical Specification 6.9.1.9.b, attached is Licensee Event Report No. 81-25, concerning a loss of powcr to -Preferred Instrument Bus Y11 lasting approximately one minute.

Sincerely, C. P. Yund t General Manager W4 C /MLD/ WON:na Attachments c: LER Distribution List iks g 8111130716 81110

~ - -

PDR ADOCK 05000344 S

pop

• i REPORTABLE OCCURRENCE 1.

Report No.:

81-25 2.

a.

Report Date:

November 2, 1981 b.

Occurrence Date: October 4, 1981 3.

Facility: Trojan Nuclear Plant, PO Box 439, Rainier, OR 97048 4.

Identification of Occurrence:

. Power to 120-Volt AC Preferred Instrument Bus Yll was lost for one minute due to a failure in its associated static inverter. This instrument bus is required to be operable by Technical Specification 3.8.2.1, as it supplies power to certain Train "A" Engineered Safeguard Feature (ESF) equipment and Reactor Protection Channel "A" equipment.

5.

Conditions Prior to Occurrence:

The plant was operating in Mode 1 at 100% power.

6.

Description of Occurrence:

Preferred Instrument Bus Yll was lost due to the failure of an output current sensing relay on inverter Y15. This inverter is the normal source of power for Bus Yll. Power was restored to Yll within one minute by transferring its source of power to a nonpreferred instru-ment bus, Y01. The failed relay (Guardian Electric, CS1-220 output current sensing relay) was replaced and the normal power supply was returned to Yll in five hours.

In addition to supplying Reactor Protection and ESF equipment, Y11 also supplies nonpreferred power to the feedwater pump speed control system and controlling level channels on two steam generators. Loss of power to these components caused an increase in feed flow to two steam generators resulting in an automatic turbine trip / reactor trip on steam generator Hi-Hi level.

7.

Designation of Apparent Cause of Occurrence:

The apparent cause of this event is attributed to normal relay end-of-life.

8.

Significance of Occurrence:

This event had no effect on either plant or public safety. The other three preferred instrument buses were all operable at the time of the occurrence and alternate power to Bus Y11 was quickly restored.

Train "B" ESF equipment was operable and available for use.

~.

Page Two 9.

Corrective Action

Electrical power was restored to the affected components within one minute and the normal Yli power supply through the inverter was returned in five hours upon replacement of the failed relay.

Additionally, inverter output current sensing relays were replaced in two other preferred instrument buses.

the fourth inverter relay will be replaced as soon as parts become available, and a preventative maintenance program is being established for periodic replacement of these current sensing relays.