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( p-OEAB EVENT TRACKIN3 SHEET NE "k
Assigned To & Event Date >= 07/14/94 & Event Date <= 07/14/94 & "$AINT LUC'E" $ Plant Nane Pltnt:
SAINT LUCIE Unit Engineer:
FIELDS N.
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EvCat:
07/14/94 Norning Report:
07/14/94 Briefing:
94-25 50.72i: 0 LER#:
050000009400000 PNf:
Oth r Notification:
Sycten:
Component:
OPERATING NODE SIGNIFICANCE 1 - Operation A - Reactor Protection System 2 - Startup B - Safety-Related Cooling System 3 Hot Stan & y C - Fuel Cladding 4 - Hot Shutdown D - Reactor Coolant Pressure Boundary 5 - Cold Shutdown E - Contairnent 6 Refueling F - Plant Power 7 Other G - Unexpected Plant Performance H - Other:
CAUSE EVENT TYPE 1 - Equipment Failure
- Significant Event 2 - Design or installation Error EO '- Event of Interest 3 - Operating Error f TBD - To Be Determined 4 - Maintenance Error OTH - Other 5 - External 6 Other i
l POTENTIAL AO:
Criterion:
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FIEtDS w. [ w T u Y..
k7h4 Engineer b
OIO Apprcved:
Section Leader A. Chaffee Branch Chief
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EVENTS ASSESSMENT PANEL First Screening:
osu Significance
Description:
FAILURE OF TRIP CIRCUIT BREAKER S TO OPENS.
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ETS-02 Page:1 07/26/94
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$$ XIC<CY G:\\ETS2.000 DOCUMENT LOCATION & NAME:
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EVENT F0ll0W-UP ASSIGNMENT SHEET i
/ ASSIGNMENT DATE:
ASSIGNED T0: Fields /Koshy i
PLANT & UNIT: St.Lucie EVENT DATE:
7-14-94 50.72 REPORT NO:
DAILY REPORT DATE/N0:
2-94-0058 j
OTHER REPORT:
EVENT
SUMMARY
AND SPECIFIC FOLLOW-UP ASSIGNMENT Evaluate the failure, prepare a brief and an info. notice if needed.
CIRCLE THE APPLICABLE CASE:
SAFETY SIGNIFICANCE CLASSIFICATION: 0TH E01 XX SIG A0 GENERIC CONCERN STATUS:
YES IN #In oreo BUL #
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OR BRIEF:
YES #
CLOSE0VT PROBLEM:
FAILURE OF A REACTOR TRIP BREAKER TO OPEN DURING A SURVEILLANCE TEST.
CAUSE:
BREAKER OPENING PREVENTED BY FOREIGN MATERIAL LODGED IN TRIP LATCH AREA.
SAFETY SIGNIFICANCE:
APPEARS TO BE A GENERIC PROBLEM WHICH MAY BE MORE SIGNIFICANT FOR BREAKERS USED IN OTHER APPLICATIONS OR INSTALLED IN NSSS OF OTHER VEND 0RS.
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DISCUSSION:
On July 14, 1994, during monthly reactor protection system (RPS) logic matrix testing, trip circuit breaker 5 (TCBS), GE model AK 2-25, failed to open (Figure 1). Operators unsuccessfully attempted to open the breaker from the control room. The breaker also could not be opened locally by either electrical or mechanical means.
TCBS had successfully opened on three previous occasions in response to previous steps in the surveillance procedure. TCBS is one of eight reactor trip breakers in the one-out-of-two takan twice reactor trip coincidence logic.
The licensee opened TCB which, with tcb5, forms one channel. The licensee also opened TCB's 2 and 6.
A plant shutdown was commenced about 3.5 Hrs. Later at the direction of the licensee's nuclear vice president.
The licensee's and GE representative's inspection of TCBS found that a small piece of phenolic material from the cutoff switch body (interrupts power to the closing coil as part of the anti-pump circuit) had broken off and become lodged in the trip latch mechanism, preventing its motion (see figures 2 and 3). A machine screw attaching the cutoff switch to its mount was found to be loose.
The licensee speculates that this loose screw allowed the switch to migrate such that its body was damaged as a result of component movement during previous breaker cycling.
GE service advisory letter (SAL) 303.0, Issued April 6, 1989, informed owners of ak 25-1 breakers of the potential for the armature of the cutoff switch developing cracks that could lead to switch failure with the potential for burning up the closing coil.
The SAL did not mention any problem with cracking in the body of the switch.
Followup:
o licensee and a vendor representative inspected all similar unit 2 breakers.
Switches were found with scratches or " mold marks" but none of the conditions were judged significant. None of the cutoff switches were found with loose screws.
Region II is reviewing the event and licensee actions in light of their compliance with appropriate technical specification action statement.
Region II will draft an information notice describing this evat.
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I FIGURE 10.1-1 SIMPLIFIED RPS 10.1-17
l BRIEFING 94-25 ST. LUCIE FIGURE 2 ST. LUCIE PLANT MAINTENANCE PROCEDURE NO. 0920071, REVISION 2 PERIODIC MAINTENANCE OF REACTOR TBIP SWITCHGEAR AND BREAKERS RGURE 12 l
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'tAINTENANCE PROCEDURE NO. 0920W1, REVISION 2 PERICO*C '.tAINTENANCE OF REACTOR 31R SWITCHGEAR AND BREAKERS MGURE 2 CUT AWAY OF FI stmtir**f I Y OPERATED AK-2 CIRCUF BREAKER
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- 1. Arc ouencher Retainer
- 8. Trip Shan
- 14. Upper Stud
- 2. Cutoff Swith 8A. Front EsczActioon 14A. Lower stud
- 3. Cutoff Switch Actuator
- 9. Cosing Solenoid
- 15. Stationary Contacts ard Spnnos
- 4. Spring Crier 9A. Locaben of slots for te. Arc Runner Maintenance Hentas
- 5. Sheutdor Pin
- 10. Closing Solenoid Armsture
- 17. Aro Ouencher WWfier
- 6. Connecang IJnk it. Cover Retainer or Ovenomd
- 15. Cerstnlo s'de Plates DmAos
- 7. Trio Laten
- 12. Lower stud 7A. Laich Roser
- 13. Soclast Head Screws