ML20006A453
| ML20006A453 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/19/1990 |
| From: | Michael Ray TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9001260280 | |
| Download: ML20006A453 (2) | |
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_ TENNESSEE VAL. LEY AUTHORITY p
, CHATTANOOGA, TENNESSEE 37401 SN 157B Lookout Place fL
!JAN 191990 a
f U.S.-Nuclear Regulatory Commission
.ATTNL Document Control Desk n
Washington, D.C.
20555 W
(,
' Gentlemen:
-In-the Matter of-
)
Docket Nos. 50-327 h
Tennessee Valley' Authority
)
50-328 SEQUOYAH NUCLEAR PLANT-(SQN) UNITS'1 AND 2 - NRC INSPECTION REPORT NO. 50-327, a
328/87-73 -- REVISED COMPLETION DATE FOR ESSENTIAL RAW COOLING WATER (ERCW)
L TEMPERATURE CONTROL VALVE REPLACEMENT COMMITMENT AND REVISION OF GROUND FAULT DETECTION ON THE.480-VOLT AUXILIARY POWER SYSTEM COMMITMENT
Reference:
TVA's response to NRC dated September 26, 1988, "Sequoyah Nuclear 0
Plant (SQN) - NRC Inspectio_n Report Nos. 50-327/87-73 and 328/87 Supplemental Response" The original schedule for replacing the subject ERCH temperature control
~
valves was December 31, 1989.
The scope of work and the cost to implement these replacements are significant; detailed cost studies were required and procurement leadtimes are considerable.
The capital project package has now-J been completed and a revised schedule has been prepared, which will support a j
completion date of March 29, 1991.
In the interim, Emergency Procedure E-1, Loss of Reactor of Secondary Coolant," has been revised to ensure that y
actions for manually starting the standby control building air-conditioning i
. units;are taken'.
f TVA is deleting the commitment t'o evaluate and reconfigure the existing circuitry on the 480-volt auxiliary power system to prw ide high resistance l
ground-detection and main control room (MCR) alarms during the Unit I refueling outage ~
TVA originally committed to evaluate.the need to upgrade existing.ctrcuitry.to provide MCR alarms as part of a deficiency identified in
.the integrated design inspection (IDI) (87-48).
This item has been closed by l
NRC' based on TVA's commitment to evaluate the concern and also based on the
~ ac'ceptance of the interim compensatory measure initiated.
Interim compensatory measures were taken by assigning an auxillary plant operator to ttest for ground faults at each distribution substation once-every shift.
In a 1
violation response to a subsequent NRC inspection on compensatory measures (87-73),'TVA referenced the proposed corrective action to totally eliminate the associated compensatory measure.
TVA has-s'nce completed the evaluation of the original concern regarding ground fault detection and MCR alarms under the corrective action associated with the IDI finding. This evaluation revealed that there is no need to upgrade the existing circuitry to provide detection and alarms, provided 1
manuel verification is performed on each shift.
TVA considers an undetectabl l
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U.S. Nuclear Regulatory Commission
-JAN 191990 Ll arcing ground fault of such magnitude to cause high. system overvoltages in one y
train of alternating current (ac) power simultaneous with a loss of coolant F
accident and a single active failure of the loss of the opposite train of ac power to be an. incredible event.
TVA determined that this scenario is not credible because it involves a coincid_ence of highly improbable events.
Both of these commftments are accordingly being closed.
However, TVA will continue the testino Nr ground faults at each distribution substation once every shift.
If you-h',ve any questions concerning this submittal, please telephone M. A. Cooper at (615) 843-6651.
Very truly yours, TENNESSEE VALLEY AUTHORITY sy Manage. Nuclear L censing and Regulatory Affairs cc: Ms. S. C. Black, Assistant Director for Projects TVA Projects Division
-U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Assistant Director for Inspection Programs TVA. Projects Division U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee. 37379