ML19343C335
| ML19343C335 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 10/19/1973 |
| From: | Hartley F CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| AO-73-10, CYH-2488, NUDOCS 8103100253 | |
| Download: ML19343C335 (2) | |
Text
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CONNECTICUT YAN K EE AT O MIC POWER COMPANY I
HADDAM NECK PLANT
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RR # 1, BOX 127E. EAST HAMPTON. CONN. 06424 6--
October 19, 1973 CYH-2488 I'l
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Mr. A. Giambusso 50-213 C
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Deputy Director for Reactor Projects 4,,,JNU Directorate of Licensing q
I United States Atomic Energy Commission Q
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Office of Regulation
\\0.'2 4.' * ?.*rM.f Washington, D. C.
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Dear Mr. Giambusso:
As defined by Tech:.ical Specifications for Connecticut Yankee the following report involving the failure of the power supply for W
the 480V Motor Control Center Number 5 (MCC-5) to automatically tran fer when the preferred feeder selector switch position was chanced g
hereby submitted as Abnormal Occurrence 73-10.
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MCC-5 is the source of power to various safety related moto 2 M 28 1973 > l operated valves and other auxiliaries.
Itspowersupplycomesfromeither480Vbus5(breaker 5-5)h Qs.nnyigna /
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fM 480V bus 6 (breaker 5-6).
Thecontrolcircuitryforthesefeeder\\
breakers is designed to allow only one of the two breakers to be k, M, x
closed at any one time. A selector switch is provided to select which b "
breaker will be the " preferred feed". With both 480V busses energized, changing the position of the preferred feeder selector switch would normally cause the previously selected breaker to trip and the other breaker to close.
At 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br /> on October 7, 1973 with both 480V busses 5 and 6 energized the preferred feed selector switch position was changed from position 1 (breaker 5-5 closed) to position 2 (breaker 5-6 closed). At this time breaker 5-5 opened but breaker 5-6 failed to close resulting in a loss of power to MCC-5. Breaker 5-6 wcs then closed manually re-turning power to the motor control center.
Subsequently, the selector switch position was cycled several times with satisfactory operation of the breakers observed each time.
A detailed investigation revealed a design deficiency in the inter-locking feature of the preferred breaker selector switch, thus setting up a trip circuit to the redundant breaker. The abnormal condition is established when either breaker 5-5 or 5-6 has been tripped electrically with the trip button or mechanically with the trip bar. The intended
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design of the system was such that when the closed breaker is tripped either with the trip push button or with the trip bar, the breaker for the alternate supply should close automatically.
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Mr. A. Giambusso-USAt.a 'Octoo.c.19, 1973
~A design change to correct the deficiency has'been proposed and is currently under review.
In the' interim period written procedures have been prepared and will be-utilized for maintenance and inspection of the breakers associated with MCC-5.
Very truly yours,.
1 p F. W. Hartley_
Plant Superintendent RHG/mb i
cc: Directorate' of Regulatory Operations i
Region 1 King of Prussia, Pennsylvania f
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