ML20003C723
| ML20003C723 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 03/15/1974 |
| From: | JERSEY CENTRAL POWER & LIGHT CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| AO-50-219-74-17, NUDOCS 8103160367 | |
| Download: ML20003C723 (3) | |
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OYSTER CREEK NUCLEAR GENERATING STATION FORKED RIVER, NEW JERSEY 08731 Abnormal Occurrence Report No. 50-219/74/17 W.d :
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March 15, 1974
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.W 6ccurrence Date March 7,1974 Identification of Occurrence Violation of the Technical Specifications, paragraph 3.7.B, when power operation of the reactor continued with the SB transformer unavailabic for service for a time period greater than the Technical Specification limit of 7 days out of any 30 day period. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, paragraph 1.15B.
Conditions Prior to Occurrence A routine plant shutdown was in progress.
The major plant parameters at the time of the event were as follows:
Power:
Electric, "100 FMe Reactor, "300 MWt 4
Flow:
Recirculation, 7.5 x 10 gpm 6 lb/hr Feedwater, 1.2 x 10 Stack Gas: =10,000 pCi/sec Description of Occurrence On Thursday, March 7,1974, at 1700, as part of the routica plant shut-down procedure, it was required to transfer plant power from the IB auxiliary transformer to the SB startup transformer. The control room operator on duty operated the closing switch for the SIB breaker with no results. The reactor shutdown was terminated, holding the generator electric power at approximately 100 MWe in order to maintain a power supply path through the IB auxiliary transformer.
Inspection of the SIB breaker revealed that the closing spring was not in the charged position; hence, breaker closure was not possible in either the manual or automatic mode. The failure of the spring to wind has been traced to a failed spring cam switch which closes when the spring unwinds.* The cam switch closure normally causes a relay, S2Y, to energize which in turn deenergizes
- See attached reproduction -of pertinent portion of General Electric Drawing No.-0223K0173, Sheet 14.
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Abnormal Occurrence No. 50-219/74/17 Page 2 the SIB breaker closing coil 52X.
Contacts from 52X in turn cause the spring winding motor to start and rewind the spring.
Since the cam itch contacts failed to cause 52Y to energize, a centinuous current was splied to 52X causing it to burn which resulted in freezing the coil auxiliary contacts in their energized position.
It is thought at this time that the failure of the spring to rewit.J occurred following the January 12, 1974 reactor shutdown operati sn, since this was the last successful operation of the breaker. After replacing the 52X coil and the failed can switch, successful transfer of load from IB auxiliary transformer to the SB startup transformer was achieved.
Apparent Cause of Occurrence Component failure was the cause of this occurrence.
The failure of the cam switch is presently under investigation.
Analysis of Occurrence The SIB breaker is intended to close automatically when the IB auxiliary transformer breaker trips.
Had the breaker been required to perform this function, it would have resulted in a loss of power to the IB and ID 4160 volt switchgear. The 1-2 emergency diesel generator would have initiated in the fast start mode and assumed load on the ID emergency b us.
Corrective Action At this time, it is thought that this occurrence is an isolated incident.
However, all 4160 volt safeguard and 460 volt safeguard switchgear will be checked to see that the closing springs have been properly charged.
In addition, the feasibility of installing a closing circuit monitoring system will be explored with the Generation Engineering Department.
Failure Data Manufacturer data pertinent to the failed switch are as follows:
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General Electric Company switch Part No. 456-A8668-5 4160V Switchgear s
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c..drol % e, 52 Limit switch for spring 52X Spring releases c.+11 52 Closing latch SMILS - charging motor contacts operates latch which ClJ1S - monitoring switch (1-2) (3-4) open and release closing springs is closed when latch is capable contact (5-6) closed when to close 52-of blocking, fully springs are fully charged.
5215 Interlock switch closed charged closing springs.
when 52 is in folly raised or fu1Ty Iowered position.
1711 = Relay Panel 1.imit SW shown with PClt 022310173 LP/DF = Gen. and Aux. Power Panel in raised position.
Sheet 14 of 15