ML20009F754
| ML20009F754 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/15/1981 |
| 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, NUDOCS 8107310514 | |
| Download: ML20009F754 (3) | |
Text
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OFFICIAL COPY TENNESSEE V ALLEY AUTHO9;i '
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400 Chestnut Street Tcwer II June 15, 1981-SQRD-50-328/81-39 fM?1 W
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Mr. James P. O'Reilly, Director JUL 3 01981 -
Office of Inspection and Enforcement i
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U.S. Nuclear Regulatory Commission
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e Region II - Suite 3100 1#
101 Marietta Street Atlanta, Georgia 30303
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Dear Mr. O'Reilly:
SEQUOYAH NUCLEAR PLANT UNIT 2 - SI ACTUATED SIMULTANEOUS MOTOR STARTING -
SQRD-50-328/81 FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector R. W. Celenjak on May 5, 1981 in accordance with 10 CFR 50.55(e) as NCR SQN EEB 8116. An interim report was submitted on June 4,19d1.
Enclosed is our final report.
If you have any questions, please get in touch with D. L. Lambert at FTS 857-2581.
4 Very truly yours, TENNESSEE VALLEY AUTHORITY 1l.
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L. M. Mills, Manager Nuclear Regulatibn and Safety Enclosure cc:
Mr. Victor Stello, Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555
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S!r 8107310514 810615 PL'R ADOCK 05000328 S
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4 ENCLOSU3E SEQUOYAH NUCLEAR PLANT UNIT 2 SI ACTUATED SIMULTANEOUS MOTOR STARTING SQRD-50-328/81-39 10 CFR 50.55(e)
FINAL REPORT Descriction of Deficiency During a review of preoperational test results, it was discovered that fer a safety injection actuation with offsite powe" available a simultaneous start signal is sent to the residual heat removal pump, safety injection pump, containment scray pump, centrifugal charging pump, component cooling system pump, and several valve operators.
During the time the first four pumps are accelerating, the voltage at the terminals of the anit 2, 350 horsepower component cooling system pumps could be as low as 354 volts cr 77 percent of rated voltage. These motors are only rated to start at 80 percent of rated voltage.
Safety Imolications The acceleration times for the four medium-voltage motors during their l
si=ultaneous starting (98 percent rated voltage).are approximately two to five seconds.
Had this resulted in overcurrent at the unit 2 component cooling system pumps during this period of time, some of these pumps could have tripped because of overcurrent and would have been unavailable for providing their safety function.
However, as stated below, the acceleration time of two to five seconds should not affect the component cooling system pump motors. Additionally, during normal operation, a minimum of three of the plant's five component cooling system pumps are already running. Should an SI occur, only one pump maximum per unit plus the swins pump would be required to start at the same time. Therefore, this conconformance will not affect the safety of the plant.
Corrective Action The component cooling system pump motor's acceeleration time at 80 percent voltage has been supplied by the vendor. Also, the overcurrent trip setting of the motor's feeder breaker has been reviewed.
It has been determined that the overcurrent relay can be set so that the motor will remain connected to the bus during the depressed voltage caused by simultaneous motor starting and then accelerate when adequate starting voltage is restored.
TVA has also completed its analysis of other 460-volt motors that may be activated by a SI signal or by process control. There are no other motors powered directly from the Class IE 480-volt switchgeer that would be-started simultaneously with the medium-voltage motors named above. There l
are several valve operators and other motors powered from Class IE 480-volt s
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motor control centers that are started at this time.
However, it was shown by testing during construction that valve operators would not trip on locked-rotor current in less than 16 seconds, and that the other motors would not trip on six times full 1.oad current in less than 12 seconds (Construction Inspection Test No. 17, Revision 3). Therefore, these motora and valve operators will remain connected to the bus during the 2-to 5-second depressed voltage caused by simultaneous motor starting then accelerate when adequate starting voltage is restored.
The depressed voltage cau.aed by simultaneous motor starting will have a duration of less than 10 seconds. As the medium-voltage motors reach normal running speed and consequently draw less current, the voltage at the 460-volt motor termin2-, will become adequate for starting. Therefore, the 460-volt motors will start 'within the same time allowed for a transfer to onsite power and will meet the safety response time. Therefore, TVA concludes that no corrective action is required for this NCR.
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