ML19323D402

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Final Deficiency Rept Re Auxiliary Feedwater Response Time. Motor Driven Auxiliary Feedwater Response Time Exceeded 60-s Requirement Due to Slow Responding Pneumatic Actuators. Level Control Valve Actuator Mods to Be Complete by 800801
ML19323D402
Person / Time
Site: Sequoyah Tennessee Valley Authority icon.png
Issue date: 05/12/1980
From:
TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19323D399 List:
References
NUDOCS 8005210529
Download: ML19323D402 (1)


Text

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ENCLOSURE SEQUOYAH NUCLEAR PLANT UNIT 2 AUXILIARY FEEDWATER RESPONSE TIME 10CFR50.55(e)

NCR SQN NEB 8009 FINAL REPORT Description of Deficiency The Sequoyah auxiliary feedwater system must be capable of delivering full flow within one minute following a blackout as stated in the FSAR, Section 10.4. This 60-second delay includes the time to start the diesels and supply power to any necessary motors, valves, and controls.

However, the preoperational test acceptance criteria for unit 1 were inconsistent with the FSAR analysis, because the time to start and seauence loads onto the diesel generator was not accounted for in the preoperational test. Consequently, the motor-driven auxiliary feedwater response time in the preop test exceeded the 60-second response time requirements. The reason for the slow response time is that the pneumatic actuators for the steam generator level control valves are clow to respond to the signal to open. These valves are held normally closed by a supply of control air to the actuator. The valve is opened by bleeding off air from the actuator through a solenoid valve. The time required for the valve to go from full closed to full open is approximately two minutes.

Safety Imolications The auxiliary feedwater system may not respond quickly enough when needed; therefore, its ability to perform its intended safety function is questionable.

Corrective Action The level control valve actuator is being modified to incorporate an exhauster. When this device is activated, it relieves the control air pressure from the actuator faster than bleeding off the air through the  ;

solenoid valve. This results in more rapid opening of the valve. '

TVA expects to coc7 1 ete this modification by August 1,1930, for preopera-tional testing. j i

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