ML20052B113
| ML20052B113 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Palisades |
| Issue date: | 12/15/1978 |
| From: | Hunter D, Jorgensen B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Warnick R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML18043A232 | List: |
| References | |
| FOIA-82-122 NUDOCS 8204300042 | |
| Download: ML20052B113 (3) | |
Text
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CLEN ELLYN. lLUNOIS 60137 December 15, 1978 Docket No.
50-255 MEMORANDUM FOR:
R. F. Warnick, Chief, Reactor Projects Section 2 FROM:
D. R. Hunter, Inspector Specialist B. L. Jorgensen, Reactor Inspector
SUBJECT:
UNM0NITORED FAILURE MODES OF 2400 AND 480 VOLT AC ELECTRICAL SWITCH GEAR A recent inspection at the Consumers Power Palisades Plant in followup of a reportable event (50-255/78-18, dated June 22, 1978), concerning the failure of a 2400 volt AC bus to transfer to the startup power source, revealed that possible unmonitored failure modes exist within the 2400 volt and 480 volt AC switchgear and certain 480 volt AC motor control centers at the Palisades Plant.
The review of the installed plant electrical breakers revealed the following types of failure modes appear to exist which can be present between surveillance testing or equipment rotation, etc., without being readily identified by the licensee:
a.
4160 Volt AC and 2400 Volt AC Stored Energy Breakers (Allis-Chalmers). The breakers sit in the " CHARGED" condition, whether open or closed, recharging after each breaker operation.
1.
No monitoring is provided for the breaker "CLOSE"' circuit since it is fused separately from the two circuits which includes the position indicator lights.
2.
No monitoring is provided to indicate that the charging springs are actually in the " CHARGED" position. The position of the charging springs can be verified locally within the breakers subsequent to each operation. The charging springs on this type breaker recharge after a "CLOSE" operation of the breakers.
b.
2400 Volt AC Solenoid Operated Breakers (Allis Chalmers).
The breakers include a trip coil and a close coil. The trip coil and fuses are monitored by the breaker indicator lights.
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4, 7N R. F. Warnick December 15, 1978
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1.
No monitoring is provided for the breaker "CLOSE" circuit-fused separately from the trip circuit.
It was noted that an undervoltage relay coil is provided for the "CLOSE" circuit voltage monitoring, but the relay was not utilized by the plant design.
'480 Volt AC Stored Energy Breakers (ITE). The breakers sit in the c.
" CHARGED" condition:in the "0 PEN" position and sit in the " UNCHARGED" condition in the " CLOSED" position.
1.
No monitoring is provided to detect a number of possible breaker failure modes including the failure of a breaker to charge.
properly and the inadvertant operation of the devices locally.
(a)- Breaker in the " CHARGED" condition when "0 PEN" - locally indicated on the breaker front panel only.
(b) Breaker charge motor power supply " TOGGLE / PADDLE" type switch - locally 'adicated on the breaker front panel only.
(c) Breaker installed fixed trip device (Magnetic) - locally indicated on the breaker front panel only.
(d)
Breaker locally operated trip / lockout lever (workman protection) - locally on the breaker front panel only.
d.
480 Volt AC Motor Control Center Breakers (Cutler-Hammer). The breakers on safety related equioment contain indicator light circuits which monitor the " THERMAL" overload trip devices and indicate an inoperable component. The Palisades plant does not appear to have experienced undetected failures of equipment due to the opening of the " THERMAL" overload devices.
Consideration should be given to providing an in-depth review of the overall problem with unmonitored failures within electrical switchgear based on GDC-21, requiring that safety related equipment "shall be designed for high,Juncripnal reifability, and GDC-23, requiring that safety relsted equipment "shall be designed to fail into a safe state or into a state demonstrated to be acceptable on some other defined basis if conditions such as disconnection of the system, loss of energy (e.g., electrical power)....are experienced."
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R. F. Warnick. December 15,1978 The' lack'of monitoring of electrical switchgear failures appears to be generic in nature.
Yr D. R. Hunter Inspector Specialist e,
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orgensen Reactor Inspector cc:
G. Fiorelli e