ML19345A823
| ML19345A823 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 11/19/1980 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NCR-SQN-EEB-803, NUDOCS 8011250295 | |
| Download: ML19345A823 (2) | |
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s 400 Chestnut Street Tower II November 19, 1980 s
N Mr. James PS O'Reilly, Director Office of In ection and Enforcement U.S. Nuclear R latory Commission Region II - Suit 3100 101 Marietta Stre Atlanta, Georgia 3 103
Dear Mr. O'Reilly:
SEQUOYAH NUCLEAR PLANT UNIT 2 - 0FFSITE POWER VOLTAGE FLUCTUATION -
NCR SQN EEB 8034 - FIRST INTERIM REPORT The subject deficiency was initially reported to NRC-0IE Inspector R. W. Weight on October 20, 1980, in accordance with 10 CFR 50.55(e).
Enclosed is cur first interim report. We expect to submit our next report by February 27, 1981.
If you have any questions, please get in touch with D. L. Lambert at FTS 857-2581.
Very truly yours, TENNESSEE VALLEY AUTHORITY L. M. Mills, Manager Nuclear Regulation and Safety Enclosure f
cc:
Mr. Victor Stello, Director (Enclosure)V Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 l
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[Q-yo ENCLOSURE SEQUOYAH NUCLEAR PLANT UNIT 2 0FFSITE POWER VOLTAGE FLUCTUATION NCR SQN EEB 8034 10 CFR 50.55(e)
FIRST INTERIM REPORT Description of Deficiency During a degraded voltage study, it was discovered that the calculations which indicated that the present ICi kV minimum voltage limit imposed on the operation of the 161 kV grid is not correct. This is because tne 161 kV limit does not ensure adequate starting voltage for all safety-related 460-volt motors.
Interim Prorygs; TVA has calculated setpoints for future degraded voltage relaying in order to ensure adequate starting voltage for all safety-related 460-volt motors (85 percent of rated voltage at the motor terminals). The current loading configuration dictates that voltage at Sequoyah must be no lower than 164 kV.
This limit requires that the common station service transformer taps be set to voltage boost position 4.
Assuming 85 percent (391 volts) voltage motor stsrting capability, the common station service transformer's (CSST) voltage taps were changed to ensure that adequate starting voltage would be available during design basis erents.
The TVA assumption of 85 percent minimum starting voltage is no, yet corroborated by the vendor. NEMA MG-1-20.45, 1969, requires induction motors to operate within 10 percent of their rated voltage. TVA has determined that in the worst case for 480-volt Class 1E distribution system loading, many 460-volt motors are not supplied with 90 percent voltage '
during starting.
At this time, TVA is attempting to obtain vendor documentation that would substantiate the 85 percent voltage starting capability.
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