ML16343A598
| ML16343A598 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 09/26/1975 |
| From: | Jennifer Davis, Thornburg H, Warnick R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| References | |
| PN-75-097, PN-75-97, NUDOCS 9807310142 | |
| Download: ML16343A598 (12) | |
Text
p75 OEAB EVENT TRACKING SHEET SORT>
Assigned To QUERY> "TAPPERT"
$ Assigned To & Assigned Date >- 06/06/95 "DIABLO CANYON" $ Plant Name Unit: l Engineer:
TAPPERT J.
Plant:
DIABLO CANYON Event:
06/06/95 50 728-0 Briefing:
Morning Report:
06/08/95 PNg:
Other Notification:
Ag.
System:
AtlAJ LERP:
050000009500000 "t oe-fo g,neo lit~ '>
Component:
OPERATING MODE SIGNIFICANCE 2
3 4
5 6
7 Operation Startup Hot Standby Hot Shutdown Cold Shutdown Refueling Other A
B C
D E
F G
Reactor Protection System Safety-Related Cooling System Fuel Cladding Reactor Coolant Pressure Boundary Containment Plant Power Unexpected Plant Performance Other: QFIJ 2
3 4
5 6
CAUSE Equipment Failure Design or Installation Error Operating Error Maintenance Error External Other EVENT TYPE SIG -
Significant Event EOI - Event of Interest W TBD - To Be Determined
.gOTH - Other POTENTIAL AO:
Criterion:
Proposed By:
TAPPERT J.
En ineer Approved:
Section Leader A. Chaffee Branch Chief EVENTS ASSESSMENT PANEL Significance
Description:
v/7/ts o4 First Screening:
kf
~g >5 V5 Dislodged plastic pieces from the contactor preventing contactor operation.
The licensee's further inspection identified several examples of potential problem in both units.
280032 95073l0142 950707 CF ADQCK 05000275 CF twlRlt; RII.K It,KIER CSPV age:
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G:(OECB)ETS EVENT FOLLOW-UP ASSIGNMENT SHEET PSE x YES NO ASSIGNMENT DATE'SSIGNED TO:
PLANT 5 UNIT:
EVENT DATE:
50.72 REPORT NO:
MR NO:
OTHER REPORT:
SPECIALTY CODE:
6-12-95 J Ta ert Diablo Can on 1
6-6-95 4-95-00-80 EVENT
SUMMARY
Dislodged plastic pieces from the contactor preventing contactor operation.
The licensee's further inspection identified several examples of potential problem in both units.
SPECIFIC FOLLOW-UP ASSIGNMENT DETERMINE DETAILS, EVALUATE SAFETY SIGNIFICANCE AND GENERIC IMPLICATIONS.
IN ADDITION, ADDRESS THE FOLLOWING SPECIFIC CONCERNS:
ASSIGNMENT OPTIONS
- IDENTIFY DISCREPANCIES FROM INITIAL EVENT INFORMATION:
YES NO
- PERFORM RISK ASSESSMENT:
YES NO N/A ESTIMATE CONDITIONAL CORE DAMAGE PROBABILITY:
YES NO N/A.
- COMPARE WITH PREVIOUS SIMILAR EVENTS:
YES NO N/A PREVIOUS SIMILAR EVENTS:
- RELATE TO ENFORCEMENT ACTIONS:
YES NO N/A
- RELATE TO USI GSI (NUREG-0933):
YES NO N/A RELEVANT USI GSI:
PREPARE TO BRIEF:
YES NO
- TARGET CLOSEOUT SCHEDULE:
N/A
v C
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- INITIALSCREENING PANEL EVENT/CONDITION SAFETY SIGNIFICANCE:
- REMAINING OR ADDITIONAL FOLLOW-UP ITEMS:
- FINAL PANEL ASSESSMENT EVENT/CONDITION SAFETY SIGNIFICANCE:
- BASIS:
RISK PROGRAMMATIC MARGIN N/A
- GENERIC FOLLOW-UP ACTION RECOMMENDED:
YES NO PRIORITY (1,2,3,4)
IN BUL GL CLOSEOUT On June 6, 1995, the AFW discharge header Steam Generator level control MOV failed to close when operated for a surveillance.
Troubleshooting found a
piece of plastic interfering with one phase of the magnetic contactor /
starter preventing contactor operation.
The licensee's further inspection found that during wire termination to the contactors, if excessive torque is applied it will rotate the upper right stationary contact with enough force to crack the plastic phase barrier material.
There were no torque specifications for wire termination. 'he affected contactors were manufactured by Westinghouse.
The licensee uses this type of magnetic contactor in 169 safety related applications.
All of the suspect contactors were inspected.
Approximately 57% of the unit one contactors and 16/o of the unit two contactors had cracks or chips in the phase barrier material.
The licensee removed any loose material identified during their inspections.
Several had free floating chips however continuity checks of the contactors identified no operability problems.
The licensee explains the difference in unit failure rates because the Unit 1 contactors are of older vintage (Approx 1970's)
(Newer contactors phase barrier material is of more rugged construction) and the fact that Unit 1 recieved a lot of additional maintenance prior to initial operation.
Westinghouse sold the division that manufactured these contactors to Cutler Hammer.
The manufacturer has no reports of previous similar failures.
The licensee has never experienced a similar failure.
The phase separation function of the barrier material is redundant to the contactor cover which also provides for phase separation.
The failure of the AFW MOV appears to be random.
Additionally, the licensee has taken measures to minimize further cracking by eliminating the requirement to check terminals tight by retorquing them.
Due to the random nature and low frequency of failure, the safety significance of this event is low.
This event is classified as an Other>
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FILE:
G:
JRT M950080.DC1 BRIEF ¹ GENERIC
RESPONSE
IN ¹ BUL ¹ GL ¹
- 1. Priorit endnote:
PRIORITY 'I: Immediate assigrwent of resources (e.g., for highly risk-significant safety concerns)
PRIORITY 2: Hear -term action (e.g., significant safety issues not warranting imnediate action)
PRIORITY 3: Long-term action (e.g.,
issues of moderate to low safety significance)
PRIORITY 4: Resource dependent action (e.g.,
items that can be deferred)
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e PRIORITY ATTENTION REQUIRED MORNING REPORT REGION IV JUNE 8 I 1995 Licensee Facilit Notification:
Pacific Gas 6 Electric Co.
Diablo Canyon 1
Avila Beach, California Dockets:
50-275 PWR/W-4-LP MR Number:
4-95-0080 Date: 06/07/95 Licensee to SRI
~eeb'ece:
FAILURE OF 4EO VOLT NAGNETIC CONTACTOR Re ortable Event Number:
N/A Discussion:
On June 6,
- 1995, when performing a surveillance test of Turbine Driven AFW Pump 1-1, the AFW discharge header Steam Generator 2-3 level control valve (AFW-2-LCV-108) failed to close when attempting to remotely close the motor-operated valve.
Investigation revealed that the associated 480 volt circuit breaker thermal overload device tripped.
The licensee completed the surveillance by manually positioning Valve AFW-2-LCV-108.
Following completion of the surveillance, troubleshooting was conducted which revealed that the Phase C contact of the magnetic contactor (AC line starter) failed to close, interrupting power to the associated motor phase and preventing motor rotation.
Further inspection revealed that the "close" contactor plastic arc box phase barrier was chipped adjacent to the Phase C contact.
The licensee determined that the cause of the thermal overload trip was due to a small piece of the plastic arc box breaking off and becoming wedged in Phase C of the contactor, effectively single phasing the motor and causing the thermal overload device to actuate.
The failure potentially affects Westinghouse Model A201K1CA, size 00, 0,
and 1 magnetic contactors.
The damage to the plastic arc box has been determined to be caused during terminal tightening at the vendor recommended torque specification.
The upper right stationary contact can be rotated during terminal tightening to contact the phase barrier material with enough force to crack and break the plastic.
The 'plastic chip can then potentially fall between the stationary and moving contact and prevent the contact from closing.
The close contactor for Valve AFW-2-LCV-108 has been replaced with a newer version of the same model Westinghouse magnetic contactor.
The licensee has determined that this type of magnetic contactor is installed in 169 safety-related applications.
The licensee is performing a
100 percent inspection of these magnetic contactors.
The licensee plans to contact the manufacturer on this issue and considers it to be a
potential generic problem for this model contactor.
Re ional Action:
The Resident Inspector is following the licensee's actions and a
conference call is being arranged with the licensee to discuss site specific and generic concerns.
Contact:
Rob Barr (817)860-8249
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~RIORITY ATTEHTIOH REQUIRED MORHIH6 REPORT - REGION IV JUNE 13.
1995 Lzcensee/Facility:
Notification:
Pacific 6as 6 Electric Co.
Diablo Canyon 2
Avila Beach. California Dockets:
50-32$
PHR/H-4-LP MR Huuber:
4-95-0084 Date: 06/ID/95 Senior Resident lnsoector
Subject:
PDATE TO HR 4-95-0080, 'Failure of 480 Volt Maonetic Contactor'eportable Event Hueber:
H/A Discussion:
This is an uodate to June 8th Mornino Report 4-95-0080 on the failure of a 480 volt sagnetic contactor.
Durino troubleshooting.
the licensee had previously noted that a sea}I chip of the naonetic contactor phase barrier aaterial prevented proper contactor operation, The troubleshootino was initiated after aotor ooerated Valve AFH-2-LCV-108 faiied to close durino surveillance testino.
The licensee has coapleted a
100 oercent inspection of all Hestinohouse Model A201K1CA Size I eagnetic contactors (the saae type that failed in Valve AFH-2-LCV-108} installed in safetv-related equipaent, A visual inspection of the internal phase barriers was oerforeed to deteraine if the phase barrier aaterial was chipped or cracked.
The insoection results revealed a nuuber of contactors with chips or cracks in the phase barrier aaterial.
The licensee reeoved the phenolic uaterial noted to be cracked and not securely bonded to the reaaining uateriaI.
Additionally.
the contactors were nanuallv overridden to enable aeasureaent of the as-found closed contact resistance readinos.
Results froa these readinos indicated that there were no other instances where the phase barrier nateriai chips interfered with proper eagnetic contactor operation.
All as-found readinos indicated that the contactors were operable.
The licensee's evaluation of the aagnetic contactors with daaaged phase barriers concluded that the daaaoed phase barriers were still capable of effectively isolating the phases.
Inspections revealed the followino qercentaqes of saonetic contactors with cracked or chioped daaaoed phase barriers'80 Volt Bus Hurber Inspected Husber w/Daaaoe Percentaoe Unit 1 Bus F
Bus 6 Bus H
43 61 52 26 36 27 60 59 52 Unit 2 Bus F
Bus 8
Bus H
43 65 52 7
11 8
16 18 15 The licensee is detereining the lono tera corrective actions for this prob}ca and has coaaunicated with the vendor.
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