PNO-II-93-058, on 930301,operators Noticed Increase in Voltage on Main Generator & 6.9 Kv Unit Boards.Caused by Rupture in Extraction Steam Line Due to Erosion.Restart Pending Completion of CAL Items

PNO-II-93-058:on 930301,operators Noticed Increase in Voltage on Main Generator & 6.9 Kv Unit Boards.Caused by Rupture in Extraction Steam Line Due to Erosion.Restart Pending Completion of CAL Items

ML20059G795
Person / Time
Site:	Sequoyah
Issue date:	10/20/1993
From:	Scott Sparks NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
CAL, PNO-II-93-058, PNO-II-93-58, NUDOCS 9311090093
Download: ML20059G795 (1)

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October 20, 1993 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II-93-058 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 the Region II staff on this date.

F9eility Licensee Emercency Classification Tennessee Valley Authority Notification of Unusual Event Sequoyah 2 Alert Soddy-Daisy, Tennessee Site Area Emergency Dockets: 50-328 General Emergency X Not Applicable

Subject:

SEQUOYAH UNIT 2 RESTART AFTER LENGTHY SHUTDOWN On March 1, 1993, Sequoyah Unit 2 was manually tripped from rated power when operators noticed an increase in voltage on the main generator and 6.9 KV Unit boards. The licensee determined the cause to be a rupture in a 10 inch extraction steam line from the high pressure turbine to the B2 feedwater heater. The rupture was attributed to erosion / corrosion.

A Confirmatory Action Letter (CAL) was issued on March 4, 1993, after the March 1, 1993 Unit 2 extraction steam line rupture. The CAL identified several activities regarding the root cause and corrective actions, and required the licensee to meet with the NRC staff to discuss the above activities and the event prior to restart of either unit.

Since that time, Unit 2 has remained in Cold Shutdown while work was progressing on the completion of CAL items, and completion of restart 1 activities in accordance with the Sequoyah Restart Plan. l After discussions between NRC and the licensee, the NRC provided concurrence for Unit 2 to startup (Mode 2) on October 18, 1993. ,

l The Sequoyah Unit 2 reactor entered Mode 2 on October 19, 1993, at 4:39 p.m.

The licensee will also obtain NRC concurrence prior to proceeding from the next hold point of 30 +/-10 percent of rated power.

HRC 24-hour shift coverage for the Unit 2 restart commenced on September 29, 1993, and will continue through 100 percent power operations.

Sequoyah Unit 1 is currently in Cold Shutdown conducting a refueling outage.

This information is current as of October 20, 1993, 7:00 a.m., hours EDT.

Contact:

Scott Sparks (404)331-5619 0

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