ML20083Q806

AO 73-11-17:on 731117,relay 945 de-energized,tripping Only 115-kV Line,Thus Leaving Plant W/O Offsite Power.Caused by Electrician Accidentally Bumping Relay.Power Restored in 10

ML20083Q806
Person / Time
Site:	Nine Mile Point
Issue date:	11/21/1973
From:	Scheider R NIAGARA MOHAWK POWER CORP.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20083Q808	List: ML20083Q806 ML20083Q811
References
8502, AO-73-11-17, NUDOCS 8303140620
Download: ML20083Q806 (2)

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( h NIAGARA MOHAWK POWER CORPORATION NIAGARA MOHAWK j 300 CRIC SOULEVARO watST SYRACUSE.N.Y 53202 November 21, 1973

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Mr. Donald J. Skovholt #

Assistant Director for Reactor Operations '-

% -7 Division of Reactor Licensing 1- -

U. S. Atomic Energy Commission "

$b Washington, D. C. 20545  %

Re: Provisional Operating License: DPR-17 q @

Docket No.: 50-220 0 -

Dear Mr. Skovholt:

This is to report a condition relating to the operation of the Nine Mile Point Nuclear Station #1 (NMPNS) in which on November 17, 1973 at 1626 hours0.0188 days <br />0.452 hours <br />0.00269 weeks <br />6.18693e-4 months <br /> a loss of incoming 115 KV occurred.

Technical Specification 3.6.3.a states:

Specification:

a. For all reac+.or operating conditions except cold shutdo.<n, there shall normally be available two 115 KV external lines, two diesel-generator power systems and two battery systems......

On November 17, 1973 the reactor was scheduled for AEC Operator Examination involving a critical demonstration. After the reactor was shutdown in the early morning (%2 a.m.) breaker R40 was opened to facilitate r.o oto line work on the 115 KV line between James A. FitzPatrick Nuclear Power Plant Eo (JAFNPP) and NMPNS #1. B: eaker RIO, the remaining 115 KV line breaker was y closed and the station was operating on reserve power supplied by this line.

ce Following the Reactor Operator critical demonstrations, the reactor was in 80 the just critical condition, moderator temperature 207 F, mode switch in

% start-up and the JAFNPP-NMPNPS 115 KV line out of service. A plant elect-g rician, working with the relay department in the auxiliary control room on ou the JAFNPP-NMPNPS 115 KV line relay accidentally bumped a relay (50 FDS/SI)

@[ causing Relay 945 to de-energize thus tripping the remaining 115 KV line.

g The plant remained without off-site power for 10 seconds until breaker R10

tiu reclosed. _ A{

Yh A reactor scram occurred within seconds (5.4) as M.G. Sets #131 and #141 \gg (which supplies power to the scram pilot solenoids) upon loss of A.C. power, J tripped at 55 hz. Within the allowable 10 seconds both diesel generator systems ly had started and energized the two control rod drive pumps to maintain reactor j w .c . ~ water within2he normal expected range for. this transient. As water-level- 3

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remained no mal no -other safeguard equipmentswas needeCOPY S

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Mr. Donald J. Skovholt '

November 21, 1973 U.S. Atomic Energy Commission Restoration of normal reserve station power occurred within 10 seconds and upon reseting necessary plant feeders normal reserve A.C. was established to plant equipment and the diesel generators shutdown.

The reactor was restarted at approximately 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> with both 115 KV lines in service and normal plant conditiens.

All systems performed their designed function as required and no hazard was presented to the general public.

To prevent a reoccurrence of this incident the plant electricians were

, made aware of the need to be extra cautious when working around relaying in ,,

articular when one line is already de-energized. '

Very truly yours, udolph R Schneider Vice President - Electric Operations RRS:cm W