United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for July 9, 2004

Headquarters Daily Report

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REGION II

Switchyard Disturbance

Licensee/Facility:

SOUTHERN NUCLEAR OPERATING CO., INC.
Hatch 1, Hatch 2
BAXLEY, Georgia
Dockets: 05000321, 05000366
[1] GE-4, [2] GE-4
License No:
Notification:

MR Number: 2-2004-0008
Date: 07/09/2004

Discussion:

At 3:10 a.m. on July 7, 2004, a ground fault on a 230 kV transmission line connected to the switchyard at the Hatch site occurred. The fault caused two protective circuit breakers in the switchyard to open. However, protective relays sensed differential current between the two switchyard busses and one of the two switchyard 230 kV busses was isolated. All plant loads (both safety and non-safety related) continued to be powered by the remaining 230 kV bus. The offsite power supplies to safety-related plant loads were not affected. Investigation into the switchyard breaker performance is continuing.

As a result of the switchyard disturbance, the Unit 1 'A' reactor recirculation pump ran back to 33% of rated flow causing a reactor power reduction to about 73%. The licensee immediately implemented actions in accordance with abnormal operating procedures to stabilize the unit. The region of potential instability on the power/flow map was not entered. The licensee has preliminarily attributed the reactor recirculation pump runback to a voltage decrease affecting a relay in the runback circuitry.

The resident inspectors have reviewed the initial response to the event and continue to monitor the licensee's event investigation.


Accession Numbers:

Accession No Accession Date
ML041910356 07/09/2004

Contacts:

Name Office Abbrev Phone No E-Mail
RAPP, CURTIS W R2 (404) 562-4674 CWR1@nrc.gov
Page Last Reviewed/Updated Thursday, March 29, 2012