ML20056G975
| ML20056G975 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 08/31/1993 |
| From: | Fenech R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9309080021 | |
| Download: ML20056G975 (2) | |
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Robert A Fenech s a evxum varvwauces num i
August 31, 1993 i
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk l
Washington, D.C. 20555
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Gentlemen:
j In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 l
l SEQUOYAH NUCLEAR PLANT (SQN) - REPLY TO QUESTIONS FROM NRC INSPECTION REPORT NOS. 50-327/93-26 AND 50-328/93-26 i
The following is TVA's reply to Caudie A. Julian's letter to i
L Mark 0. Medford dated July 21, 1993, which requested information concerning the June - 14,1993, circuit breaker trip that resulted in the start of the emergency diesel generators.
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The event of June 14 was similar to an event that occurred on I
December 19, 1991. The latter event involved a current transformer (CT) f on the main generator.
In both cases, a CT was wired with the "Kl" and
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'tX2" secondary connection points rolled.
The main generator event involved Modifications personnel replacing the secondary wiring on a CT.
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The secondary wiring was replaced such that the X1 and X2 points were rolled. The cause of this event was determined to be the failure to i
follow procedures. Modifications electricians failed to procure the l
proper design drawing before implementing the modification. The June 14 i
event involved the replacement of a CT.
The cause of this event was the j
failure to uniquely identify the CT secondary wiring in accordance with site procedures in order to ensure correct retermination of the wires, j
The corrective action for the main generator event was somewhat narrow in j
scope in that it addressed Modifications' improvements when working on main generator cts. The corrective action process has undergone changes l
to ensure that appropriate actions are implemented to prevent recurring
-events.
SQN management will continue to communicate the lessons learned l
from this type of event and reinforce the appropriate work ethic in order 1 l
to minimize these events.
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i Page 2 August 31, 1993 i
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The corrective action for the June 14 event included identifying all 6.9-kilovolt (kV) cts that had been replaced in order to ensure that proper installation had occurred. This investigation did not discover any further discrepr.ncies. However, subsequent testing on a 6.9-kV common board revealed an incorrectly wired CT in the 1A normal feeder breaker circuitry. Procedures were developed to perform phase testing of all 6.9-kV cts that had not been tested upon replacement. The open work.
documents were also reviewed to ensure phase testing of any future replacement cts. The site procedure that governs configuration control of maintenance activities has been revised to clearly require the unique identification of each configuration change. The site procedure that contains the postmaintenance test (PMT) matrix has been revised to
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specify the proper PMT for all future CT replacements.
Based on the corrective actions taken and the lessons learned from this i
event, TVA is confident that future events involving incorrectly wired cts will not occur. TVA has previously reported additional details of this event in Licensee Event Report 50-327/93015.
I If you have any questions concerning this submittal, please telephone l
K. E. Meade at (615) 843-7766.
i Sincerely,
{:j Robert A. Fenech cc:
Mr. D. E. LaBarge, Project Manager l
U.S. Nuclear Regulatory Commission l
One White Flint, North l
11555 Rockville Pike l
Rockville, Maryland 20852-2739 1
NRC Resident Inspector
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Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Regional Administrator U.S. Nuclear Regulatory Commission v
Region 11 101 Marietta Street, NW, Suite 2900
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Atlanta, Georgia 30323-2711
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