ML20043F394

LER 90-008-00:on 900505,energizing of Sequencer Initiated Undervoltage Sequence Causing ESF Bus a to Deenergize. Caused by Incorrectly Installed Undervoltage Circuit Agastat Relay.Relay rewired.W/900604 Ltr

ML20043F394
Person / Time
Site:	Summer
Issue date:	06/04/1990
From:	Bradham O, Higgins W SOUTH CAROLINA ELECTRIC & GAS CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-008, LER-90-8, NUDOCS 9006140467
Download: ML20043F394 (4)

Text

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10CFR50.73

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't June 4, 1990 t

Document Control Desk

.U. S. Nuclear Regulatory Commission Washington, DC 20555  ;

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SUBJECT:

Virgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12 LER 90-008

~ Gentlemen:

Attached is Licensee Event Report No.90-008 for the Virgil C. Summer Nuclear Station. This report is submitted pursuant'to the requirements of 10CFR50.73(a)(2)(iv).

Should there be any questions, please call us at your convenience.

Very truly yours,

0. S. Bradham h

l' DCH/0SB:1cd l

Attachment c: 0. W. Dixon, Jr./T. C. Nichols, Jr.

-E. C. Roberts R. V. Tanner J. C. Snelson

('. S. D. Ebneter NRC' Resident Inspector J. J.. Hayes, Jr.

J. B. Knotts, Jr.

General Managers INP0 Records Center C. A. Price ANI Library G. J. Taylor Marsh & McLennan J. R. Proper NPCF  !

! R. B. Clary N59C F. H. Zander RTS (0N0900055)

T. L. Matlosz Files (818.05 & 818.07)

K. E. Nodland i

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LICENSEE EVENT REPORT (LER)-

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~"] vas n, r . - areterro susessiou carri ""X] no  ; i i A=T n ACT w . . ,a a . ,.. , . ,,. <. ,-n ,. , n .i On May 5, 1990, preparations were being made to perform Surveillance Test Procedure (STP) 125.008, "D/G A Refueling Operability Test." This required that the "A" load sequencer be re-energized. When the operator energized the sequencer, the sequencer initiated an undervoltage sequence. This caused the "A" ESF bus to be de-energized, all loads to be disconnected from the bus, and the "A" D/G to start and load onto the i bus. Operations recognized that the sequencer should not have actuated and deenergized the sequencer to interrupt the sequence. Operations then evaluated the equipment' status and manually placed the equipment in its proper configuration.

Investigation showed that an undervoltage circuit Agastat relay had been replaced on April 27, 1990, under an equipment qualification program. Upon inspection it was discovered that the undervoltage circuit Agastat relay should have been installed in the "normally open" configuration, but instead was incorrectly installed in the "normally closed" configuration. Therefore, when the sequencer was energized, the sequencer responded as if an actual undervoltage condition existed. The electrical personnel that replaced the relay had erroneously wired the new relay contacts. The .

relay was rewired in the correct configuration, verified and tested. Also a meeting by the Management Review Board was held to review the event and ensure adequate resources were being applied to correct the problem.

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DOCKET NUMSER Gl Lth NUMBER (6) PAOS (3)

.: Virgil C.: Summer Nuclear Station , , , -

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e PLAN 1 IDENTIFICATION: -i Westinghouse - Pressurized Water Reactor

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, EQUIPMENT IDENTIFICATION: I

_ Diesel Generator IEEE - DG I

'Agastat Relay IEEE - RLY  !

L IDENTIFICATION OF EVENT:

l l An' inadvertent start of'an ESF component ("A" Diesel Generator) occurred due to  !

L personnel error involving the installation of an Agastat relay in the. load i

sequencer. q i

, EVENT DATE AND TIME:

l:

! May 5, 1990, at 1515 hours0.0175 days <br />0.421 hours <br />0.0025 weeks <br />5.764575e-4 months <br />.

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REPORT DATE: l

,. - June 4, 1990- >

This. report was initiated'by Off-Normal Occurrence Report 90-055.

CONDITIONS PRIOR TO EVENT.

The plant was in Mode 5 af ter core reload in its fifth refueling outage. - The "A.

train' service water, component cooling water, HVAC chiller and reactor make-up q water. systems were.in operation with the "A" train sequencer de-energized. Diesel Generator-(D/G) "A" was in standby status.

DESCRIPTION OF EVENT:

On-May 5, 1990, preparations were being made to perform Surveillance Test Procedure (STP) 125.008, "D/G A Refueling Operability Test." This required that the "A" load ',

. sequencer be re-energized. When the operator energized the sequencer, the sequencer. initiated an undervoltage sequence. This caused the "A" ESF bus to be.

de-energized, all loads to be disconnected from the bus, and the "A" D/G to start and load onto the bus. The Shift Supervisor recognized that the sequencer should  ;

.not have actuated, and he instructed the operator to de-energize the sequencer.

This stopped the sequencer before it had completed the undervoltage sequence. The only equipment started by the sequencer was the "A" motor driven emergency feedwater (MDEFW) pump which was immediately secured by the control room operator.

The "A" service water system was immediately started to support the "A" D/G. The "A" component cooling water, reactor make-up water and HVAC chiller systems were i

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. LICENSEE EVENT REPORT 1LER) TEXT CONTINUATION - mRovto ous so. mo.oio4 j Li expires staiss F ACILITY hAME (1) DOCKET NUMBER (2) LER NUMSER tel PME m TVirgil C. Sumer Nuclear Station - vsaa -

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restored.a short time later. After verifying proper operation of the "A" D/G_and

. restor.ing off-site power to the ESF bus, the "A" D/G was secured and returned to ,

standby.

CAUSE OF EVENT: l An investigation showed that the undervoltage circuit Agastat relay had been

' replaced on April 27', 1990, under an equipment qualification program. Upon inspection.it was discovered that the undervoltage circuit Agastat relay should  ;

have been installed in the "normally open" configuration, but instead was ';

incorrectly installed in the "normally_ closed" configuration. -- Therefore, when' the sequencer was energized, the sequencer responded as if an actual undervoltage- 'l condition existed. The electrical maintenance personnel that replaced the relay l made an error recording the "as found" positions of.the relay terminations when preparing to remove the old relay. This led to the new relay being installed ,

incorrectly. This occurred even though an independent verif.ication and a Quality Control' inspection was performed'with respect to the "as found" and "as left" status of the terminations. The procedural guidance governing the maintenance is clear and should-have prevented =the error from occurring, j' ' ANALYSIS OF EVENT,:

The personnel error resulted in a false logic being sent to the sequencer. This caused the sequencer to process an undervoltage sequence even though an undervoltage condition did not-exist. All equipment functioned as expected and Technical Specifications were complied with throughout the event. Therefore, no safety consequences existed during the event.

IMMEDIATE CORRECTIVE ACTIONS:

1. Operations recognized that the sequencer should not have actuated and deenergized the sequencer to interrupt the sequence.- Operations then evaluated the equipment status and manually placed the equipment in its proper configuration.

2. The relay was rewired in the correct configuration, verified and tested.

ADDITIONAL CORRECTIVE ACTIONS:

A meeting by the Management Review Board was held to review the event and ensure adequate resources were being applied to correct the problem. This resulted in the following:

1. The personnel involved were counseled on proper verification methods.

2. A retest procedure is being considered that, if practical, will test the

'Agastat relay without creating a false undervoltage signal.

DRIOR OCCURRENCES:

None.

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