05000366/LER-1985-038-02, Corrects Unit Number for LER 85-038-02

Corrects Unit Number for LER 85-038-02

ML20214D265
Person / Time
Site:	Hatch
Issue date:	11/04/1986
From:	Gucwa L GEORGIA POWER CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
SL-1438, NUDOCS 8611210444
Download: ML20214D265 (1)

LER-1985-038, Corrects Unit Number for LER 85-038-02

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
3661985038R02 - NRC Website

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Telephone 404 S26 6526 unit numbar.

Mailsng Ariaress:

Post Office Box 4545 Atlanta, Georgia 30302 Georgia Power L T. Gucws tv. caeo reyfnc sp3teir '

Manager Nuclear Safety and Licensing 0166C November 4, 1986 U. S. Nuclear Regulatory Comission Document Control Desk Washington, D. C.

20555 Attached is Licensee Event Report 50-366/1985-038, Rev.

2.

This report meets the reporting requirements of 10 CFR 50.73(a)(2)(iv).

Sincerely, ntr -F - -

e L. T. Gucwa LGB/lc Enclosure c: Georgia Power Company Nuclear Regulatory Commission f1r. t. P. O'Reilly Dr. J. N. Grace, Regional Administrator Mr. J. T. Beckham, Jr.

Mr. P. Holmes-Ray, Senior Resident Mr. H. C. Nix, Jr.

Inspector - Hatch GO-NORMS

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ASST 1 ACT <tuswt le #400 assces, t e., seerewnevery Missa ya,ee spece typewerrren anset (161 At approximately 0200 CST on 12/22/85, with Unit 2 operating at 2428 MWt (approximately 100% rated power), plant personnel determined that power had been lost on the "A" R2 actor Protection System (RPS) bus.

This loss of power resulted in a half reactor scram; a half group isolation signal on primary containment isolation valves in valve groups 1, 2, and 5; a trip of the main steam line radiation monitors 2Dll-K603A and 2Dll-K603C; and the automatic start of the

'A' standby gas treatment train.

An immediate investigation determined that subsequent to the performance of the weekly "APRM INSTRUMENT F. T.

C." procedure (34SV-C51-002-2), operations personnel were replacing the cover on reactor scram relay 2C71-K14C when the relay's coil power supply fuse blew and de-energized the relay. This tripped the output circuit breakers on RPS motor / generator set 2C71-S001A, resulting in the loss of power on the "A"

RPS bus, and a reactor-half-scram.

Subsequent to replacing the relay fuse, the half scram was reset, and the plant rsturned to normal operation at approximately 1000 CST on 12/22/85.

Plant engineered safety f eatures responded to the loss of power on the "A" RPS bus as expected. Thercfare, the health and safety of the public were not adversely affected.

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This 30 day LER is required by 10CFR 50.73 (a) (2) (iv) because of the unplanned actuation of Engineered Safety Features (ESPs).

At approximately 0200 CST on 12/22/85, with the plant operating at 2428 MWt (approximately 100% rated power), plant personnel determined that power had been lost on the

'A' Train of the Reactor Protection System (RPS).

An immediate investigation showed that the following sequence of events took place:

1.

The required weekly performance of the "ARPM INSTRUMENT F. T. &

C." procedure (34SV-C51-002-2) had just been completed.

2.

Following completion of that procedure, operations personnel were replacing the cover (it had been removed for visual observation of the relay) on reactor scram relay 2C71-K14C when the coil power supply fuse on that device (2C71-F14C) blew.

3.

The blowing of the fuse de-energized the scram relay and tripped the "A"

RPS bus motor / generator set (2C71-S001A) output breakers, resulting in loss cf power on RFS bus "A".

4.

The loss of power on the "A" RPS bus resulted in the following:

a.

A reactor half-scram signal occurred.

b.

A half-group isolation signal was received for certain primary containment isolation valves in valve groups 1, 2, and 5.

The following valves isolated as required:

1) Reactor water sample line inboard isolation valve 2B31-F019 (group 1).

2) Drywell equipment drain sump discharge inboard isolation valve 2Gll-F019 (group 2).

3) Drywell floor drain sump discharge inboard isolation valve 2Gll-F003 (group 2).

4) Reactor water cleanup system inboard suction isolation valve 2G31-F001 (group 5).

c.

Main steam line radiation monitors 2Dll-K603A and 2Dll-K603C went to their fail safe condition (tripped) on loss of supply voltage.

d.

The

'A' Standby Gas Treatment automatically started.

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Oparations personnel immediately began an investigation to identify the cause of the blown fuse; however, the cause was not positively identified.

It is postulated that during the replacement of the cover on 2C71-K14C, the relay was bumped, thus causing ons or more energized relay contacts to briefly contact a neutral point within the rolcy. This contact caused a momentary surge of current of sufficient strength to blow ths fuse, and at the same time cause the RPS motor / generator output circuit breakers to trip.

It should be noted that the removal / replacement of the relay covers is an extremely tedious action, and it must be performed weekly for the surveillance earlier spscified.

Subsequent to the investigation, the following actions were taken to restore tne Unit to normal operating status:

1.

Reactor scram relay fuse 2C71-F14C was replaced.

2.

The RPS motor generator set (2C71-S001A) output circuit breakers were reset.

3.

The half-group isolation signal was reset, and each of the valves which had isolated was returned to its normally open position.

4.

The supply power for Main Steam Line radiation monitors 2Dll-K603A and 2Dll-K603C was restored.

5.

The "A" Standby Gas Treatment train was shut down, and its controls were returned to the standby mode.

6.

The reactor half-scram was reset.

Subsequent to the above actions, the plant resumed normal operation at approximately 1000 CST on 12/22/85.

After er t'.gineering evaluation of the event, the "APRM INSTRUMENT F. T.

C."

procedure (34SV-051-002-2) was revised on 07/31/86 to eliminate the requirement to remo\\t the covers from reactor scram relays (2C71-K14A through H) when the weekly funct. onal test and calibration is performed. The weekly status of the reactor scram relay.c is verified by the reactor auto scram trip system alarm annunciator on control room ptnel 2Hil-P603.

The " Reactor Protection System /APRM LSFT" procedure (34SV-C71-006-2), whose effective date is 10/6/86, now accomplishes the 18 month logic system functional test requirement for the reactor scram relays.

The reactor scram relay covers will be removed during parformance of procedure 34SV-C71-006-2 to verify reactor scram relay function once svary 18 months, instead of weekly as previously required by procedure 34SV-C51-002-2.

Procedure 345V-C71-006-2 satisfies the requirement of Technical Specifications section 4.3.1.2, item 2.

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.ssumwmacs -mewnn There have been no past e.milar events where a RFS bus lost its power because of a blown reactor scram relay fuse.

Plant engineered safety features responded as expected to the loss of power on the "A"

RPS bus.

Therefore, the health and safety of the public were not adversely affected by this event.

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