PNO-II-96-069, on 961005,potential Transformer in Plant 500 Kv Switchyard Exploded.Cause Determined to Be Unusual Event. Licensee Has Developed Plans for Damage Assessment,Repairs, Investigation & Root Cause Analysis

PNO-II-96-069:on 961005,potential Transformer in Plant 500 Kv Switchyard Exploded.Cause Determined to Be Unusual Event. Licensee Has Developed Plans for Damage Assessment,Repairs, Investigation & Root Cause Analysis

ML20128K679
Person / Time
Site:	Sequoyah
Issue date:	10/07/1996
From:	Lesser M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
PNO-II-96-069, PNO-II-96-69, NUDOCS 9610110141
Download: ML20128K679 (1)

'

i October 7, 1996 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II-96-069 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by Region II staff in Atlanta, Georgia on this date.

Facility Licensee Emercency Classification

, Tennessee Valley Authority X Notification of Unusual Event Sequoyah 1 2 Alert Soddy-Daisy, Tennessee Site Area Emergency l Dockets: 50-327,50-328 General Emergency l Not Applicable l

Subject:

SEQUOYAH POTENTIAL TRANSFORMER EXPLOSION IN THE SWITCHYARD On October 5, 1996, at 1:13 p.m., a potential transformer (PT) in the Sequoyah 500 kv switchyard exploded, causing a loss of the switchyard Bus 1. Switchyard relays sensed the electrical fault as designed, and power circuit breakers opened to clear the differential fault. The units experienced various control board alarms but no plant equipment was affected. Both Sequoyah units continued to operate at full power. Oil from the faulted PT sprayed onto the gravel in the switchyard and ignited during the event. The fire was extinguished in approximately 16 minutes.

There were no injuries. At 2:12 p.m., the licensee declared and exited an Unusual Event due to an explosion within the protected area.

, In addition, shrapnel from the explosion damaged the 500 kv to 160 kv intertie transformer, as well as other components in the switchyard such as insulators.

The licensee has developed plans for damage assessment, repairs, investigation, and root cause analysis. TVA has had some media interest in the event and will respond to further inquiries but does not plan a press release.

The NRC Senior Resident Inspector responded to the site to review immediate licensee activities. Additional NRC review of the issue is ongoing.

The State of Tennessee was notified.

This information is current as of 9:00 a.m., on October 7, 1996.

Contact:

Mark S. Lesser (404)331-0342 hopO1j041 961007 PNO-II-96-os9 pgg t E3+

11003"7 oh