05000271/LER-1987-001, :on 870107,reactor Protection Sys Motor Generator Set Tripped,Resulting in Half Scram & Initiation of ECCS Sys.Caused by Failed Coil on Control Relay Due to End of Life.Coil Replaced

:on 870107,reactor Protection Sys Motor Generator Set Tripped,Resulting in Half Scram & Initiation of ECCS Sys.Caused by Failed Coil on Control Relay Due to End of Life.Coil Replaced

ML20210T727
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	02/06/1987
From:	Pelletier J VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-87-001, LER-87-1, VYV-87-002, VYV-87-2, NUDOCS 8702180288
Download: ML20210T727 (3)

LER-1987-001, on 870107,reactor Protection Sys Motor Generator Set Tripped,Resulting in Half Scram & Initiation of ECCS Sys.Caused by Failed Coil on Control Relay Due to End of Life.Coil Replaced

Event date:
Report date:
2711987001R00 - NRC Website

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At approximately 12:20 hours on 1/7/87 with the plant at full power, a Reactor Protection System (RPS) Motor Generator set (MG) tripped. The resulting loss of power to half of RPS caused a half SCRAM, a Group 3 primary containment isolation, shutdown of Reactor Building ventilation and start of the Standby Gas Treatment System.

The trip of the MG set was caused by a failed coil (open circuit) on a control relay in the MG set. The reley/ coil operated for approximately 15 years and its failure my te attrib'.ted to end of life.

The events of this report did not have adverse saf ety implications. The RT'S snd Primary Contairment Isolation System (PCIS) operated as designed upon experiencing a power loss to half of RPS.

No specific actions beyond replacing the failed relay coil were determined to be necessary. We will continue to trend failures of this type and initiate additional corrective actions as necessary.

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w =c -.mn DESCRIPTION OF EVENTS At approximately 12:20 hours on 1/7/87 with the plant at full power the 'B' Reactor Protection System Motor Generator (RPS MG) set tripped.

The resulting loss of power to half of RPS caused a half SCRAM, a Group 3 primary containment isolation, shutdown of Reactor Building ventilation and the start of the Standby Gas Treatment System. The event was reported to plant management by the Shift Engineer.

CAUT OF EVENTS The trip of the MG set was caused by a failed coil (open circuit) on a General Electric CR120 series control relay in the MG set. The Energy Industry Identification System (EIIS) component identifier for the failed relay is RLY.

It is believed that the relay was original plant equipment and the coil failure is attributed to end of life (i.e., approximately 15 years operation).

ANALYSIS OF EVENTS The events of this report did not have adverse safety implications. The RPS and Primary Containment Isolation Systems (PCIS) operated as designed. A half SCRAM is the expected response due to loss of power to half of RPS.

The PCIS System is designed to shutdown Reactor Building ventilation, start Standby Gas Treatment and initiate a Group 3 isolation upon a single upscale trip of the Reactor Building or Refuel Floor radiation monitors. The de-energization of half of RPS simulated this condition by dropping out the associated logic relays.

Following the trip of the MG set, operator action restored power to the "B" side of RPS almost immediately by using the RPS alternate pcwer source.

The half SC9AM and the Group 3 isolation were reset, Reactor Building ventilation was restarted and the Standby Gas Treatment System was secured within ten minutes.

After replacement of the control relay coil, the MG sit was returned to sar-vice in approxirately 2 tnurs.

There have betti no other s'.milar failures of CR120 reitys in the RPS system.

A similar result occurred from failure of a CR205 contactor which caused a full SCRAM and a Group 3 isciation. This event was reported to the ccmmission under LER 86-10.

CORRECTIVE ACTIONS

No specific actions beyond replacing the failed relay coil were determined to be necessary. We will continue to trend failures of this type and initiate i

additional corrective actions as necessary.

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' VERMONT YANKEE NUCLEAR POWER CORPORATION ~

P. O. BOX 157 GOVERNOR HUNT ROAD VERNON, VERMONT 05354 February 6,1987 WV 487-022 U.S. Nuclear Regulatory Commission Document No. 50-271 Washington, D.C.

20555 REFERENCE: Operating License DPR-28 Docket No. 50-271 Reportable Occurrence No. LER 87-01

Dear Sirs:

As defined by 10CFR50.73, we are reporting the attached Reportable Occurrence as LER 87-01.

Very truly yours, VERMONT YANKEE NUO_ EAR POWER CDRPORATION h

p Plant Manager James P. Pelletie PBC/ mmh cc: Regional Administrator USNRC Office of Inspection and Enforcement Region I 631 Park AveRJe Xing of Prussia, Pennsylvania 19106 1

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