IR 05000324/1993017
| ML20035F309 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 04/06/1993 |
| From: | George Macdonald, Moore R, Shymlock M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20035F305 | List: |
| References | |
| 50-324-93-17, 50-325-93-17, NUDOCS 9304210137 | |
| Download: ML20035F309 (9) | |
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UNITED STATES NUCLEAR REGULATORY COMMisslON 5.}
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o REGION ll j
101 MARIETTA STREET,N.W.
- ATLANT A, G EORGI A 30323
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Report Nos.:
50-325/93-17 and 50-324/93-17
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i Licensee:
Carolina Power and Light Company
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P.O. Box 1551 Raleigh, NC 27602 l
I Docket Nos.:
50-325 and 50-324 License Nos.:
Facility Name:
Brunswick 1 and 2 i
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Inspection Conducted:
March 8-12, 1993 Inspector hl 6?tf,
2-Y W. Moore -
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Date SiQned'
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Date Signed i
3 /2 4/93 i
. MacDonald Approved by:
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M. Shymlock', Chief Date Signed
Plant Systems Section
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Engineering Branch
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Division of Reactor Safety
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SUMMARY l
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Scope:
l This routine announced inspection was conducted in the area of electrical j
maintenance.
Included in this review was the licensee's PN-30 methodology for j
the prioritization and scheduling of electrical maintenance, Restart item B-1 associated with LER 92-017 application to 4.16 kV breakers, the licensee's evaluation of NRC Information Notice 89-29, and the licensee's identification i
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of a failure mechanism for Westinghouse 480 V molded case circuit breakers.
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Results:
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Prioritization and scheduling of outstanding electrical maintenance was
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adequate; no concerns were identified with respect to outstanding electrical l
maintenance and Unit 2 restart.
Restart item B-1 remains open pending NRC l
management review of the licensee's schedule for refurbishment of the 4.16 kV ABB safety related breakers and the justification for not refurbishing these j
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breakers prior to Unit 2 restart. Appropriate actions were implemented to
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resolve the issues of NRC IN 89-29. This information was requested in NRC
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Report No. 50-325,324/93-11. The licensee's actions to correct Westinghouse
MCCB problems were good. The Westinghouse MCCB issue demonstrated an example
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of good problem identification and root cause analysis performance by the
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I technical support organization. No violations or deviations were identified.
9304210137 930408 i
PDR ADOCK 05000324 O
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REPORT DETAILS 1.
Persons Contacted Licensee Employees
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C. Bowman, Technical Support Engineer
- S. Callis, Licensing J. Cannon, Technical Support Engineer r
- T. Eason, Quality Control Supervisor
- R. Godley, Compliance Manager
- M. Kirkland, Electrical System Engineer
- J. McGowan, Compliance Specialist
- D. Moore, Unit 1 Maintenance Manager
- R. Morgan, Unit 1 Plant Manager T. Simonson, Technical Support Engineer NRC Personnel I
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- R. Prevatte, Senior Resident Inspector
- Attended Exit Interview l
Acronyms and abbreviations are identified in paragraph 7.
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2.
Electrical Maintenance (Components & Systems) Observation of Work and Review of Quality Records (IP 62705)
I This inspection included a review of the licensee's prioritization and scheduling of outstanding electrical maintenance prior to restart of Unit 2.
The licensee's guidance for this maintenance prioritization was provided by plant procedure, PN-30, Integrated Recovery Methodology, revision 1.
Outstanding maintenance included the maintenance backlog, which was defined as outstanding work identified prior to September 26,
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1992, and new work, which was work identified after that date. All
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outstanding work was identified in a system IBIR which was developed and tracked by the responsible system engineer. The IBIR scope included the spectrum of work identification mechanisms at the station, i.e. WR/J0s,
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EWRs, EERs, and Technical Support action items.
Procedure PN-30 defined the IBIR scope and provided the criteria for categorizing work for scheduling as prior to and after restart. An exception process was provided for rescheduling of work which was initially categorized as pre-restart work.
The inspectors reviewed this process as applied to current identified j
outstanding electrical maintenance. The following safety related electrical systems' outstanding maintenance items were reviewed:
4.16 kV, 480 V, 120 VAC, 250/125 VDC, and the EDGs.
In particular, the l
inspectors reviewed the outstanding maintenance to verify that all maintenance was accomplished which could impact the Unit 2 restart l
capability.
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A.
4.16 kV System There were approximately 40 outstanding work items remaining in
the 4.16 kV system IBIR. Nine of these items were categorized as pre-restart tasks and were scheduled for performance prior to Unit 2 restart.
Several of these work tasks were field complete, however, the documentation had not been closed. The remaining items were scheduled to be performed after the restart.
Examples of post-restart work included evaluations for direct replacement of obsolete equipment, breaker cabinet door fasteners needing replacement, cable tray cover deficiencies, and several items regarding the condition of non-safety related 4.16 kV breakers.
The post restart items did not impact safety related equipment needed for Unit 2 operation. Review of thL 4.16 kV IBIR verified that outstanding electrical maintenance on this system had been appropriately prioritized and scheduled.
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480 V System There were approximately 160 outstanding work items remaining in the 480 V system IBIR. Thirty seven of these items were
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categorized as pre-restart tasks with the remaining items scheduled to be performed after restart. Of the total 160 outstanding work items, 47 were for work on safety related equipment and 26 of these 47 items were scheduled prior to restart.
There were three PN-30 exceptions on the 480 V system.
Examples of post restart work in the 480 V system included MCC and 480 V switchgear indicator lamp repairs, minor cosmetic repairs, temporary power modifications, and evaluations for obsolete equipment. All PM activities listed in the 480 V system IBIR were
scheduled as restart items.
The inspectors reviewed WR/JO 92AGJL1 on the 28-2 Battery Charger AC Circuit Breaker. This item was to replace the existing GE F-frame MCCB due to concerns identified in GE Potentially Reportable Condition 91-06.
The concern was that the remote trip
functions may fail to trip the breaker when the breaker has been carrying loads greater than 50 percent for extended periods 2 or more hours. Due to the station's normal battery loading of less than 30 percent, with resultant low temperatures, the MCCB was
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scheduled to be replaced post restart during the next refueling outage. The inspectors reviewed the licensee's evaluation and the vendor's assessment and concluded that the item was appropriately categorized.
There were three PN-30 exceptions on the 480V system.
One exception, EER 87-0836, addressed coordination between safety related 480 V MCC feeder protective devices and the upstream 480 V emergency bus feeder breakers supplying the MCCs. This work item, completion of a full coordination study, was categorized as a post restart item.
Plant modification packages replaced equipment,
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I i.e. breakers, overloads,. and overload heaters, in safety. related
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MCCs to improve equipment protection and to meet Equipment l
Qualification requirements. The current 480 V unit substation i
breaker refurbishment included replacement of the existing trip l
units with new solid state trip units. The EER. identified several
cases where the calculated fault currents for faults at the MCC
were higher than the setting of the upstream emergency substation
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feeder breaker instantaneous trip, e.g. a lack of breaker
coordination.
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It was not clear to the inspectors that the licensee's initial
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evaluation, which temporarily accepted this condition,
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incorporated the different trip unit characteristics between the
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original and the refurbished breakers.
The new trip units had lower instantaneous trip settings. The original coordination
calculations contained conservative assumptions and did not
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include MCC feeder cable impedance. The licensee provided the
inspectors information containing data from calculation BNP-E-2.005 which had been developed in support of the trip unit
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replacement design package. The inspectors reviewed the l
evaluation and verified that the justification was adequate and i
that all aspects of the hardware had been incorporated into the
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evaluation. The inspectors concluded that delaying the i
coordination study until after Unit 2 restart did not impact plant t
operations. Review of the 480 V System IBIR and the PN-30 i
exceptions verified that outstanding maintenance had been
appropriately prioritized and scheduled.
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120 VAC System
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There were approximately 50 work items identified in the 120 VAC IBIR. There were no restart items and no outstanding maintena'nce'
on safety related equipment. The majority of open work items were
associated with work on non-safety related distribution cabinets.
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Review of the 120 VAC IBIR verified that outstanding maintenance
had been appropriately prioritized and scheduled.
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250/125 VDC Systems i
There were approximately 39 outstanding work items remaining in.
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the 250/125 VDC Systems IBIRs. Ten of these items were j
categorized as pre-restart items and were scheduled for
performance prior to Unit 2 restart. Several of the outstanding items were field complete with documentation closecut remaining.
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There were 25 PN-30 exceptions on the 250/125 VDC Systems.
Examples of post restart work included termination of spare cable leads, battery trolley supports, cabinet hardware repairs, and formal completion of temporary modifications. The PN-30 exceptions consisted of DC switchboard PMs, battery and feeder breaker PMs, distribution panel breaker PMs and the alternate DC supply source verification to the ESS panels.
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The switchboard, battery breaker, and feeder breaker PMs required
operational mode 5, the plant was in mode 4.
Visual inspections,
breaker cycling and thermography will. be performed prior to
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I restart.
Distribution panel breakers will receive PM prior to restart.
The inspectors reviewed the PN-30 exceptions and
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concluded that the exceptions were justified and that the
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alternate PM specified was adequate. Review of the 250/125 VDC
Systems IBIR and the PN-30 exceptions verified that outstanding
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maintenance had been appropriately prioritized and scheduled.
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EDG System l
There were 11 outstanding electrical maintenance work items on the
'f EDG system IBIR. All of these items were categorized as post-
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restart work.
Five of the eleven items were standing work orders
authorizing connection of I&C test equipment during periodic
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testing. The remaining items were for resolution' of minor deficiencies such as meters and panel tag numbers.
Review of the IBIR verified that EDG electrical maintenance was appropriately
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prioritized and scheduled.
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The inspectors reviewed the IBIRs associated with the mechanical l
maintenance for the EDG and its support systems. There were
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approximately 140 outstanding mechanical maintenance work items
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associated with these four IBIRs. Thirteen items were identified
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as pre-restart work. These items were either field complete, j
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exemption and post restart rescheduling. The inspectors concluded l
that all outstanding work necessary for Unit 2 operation was l
accomplished or would be accomplished prior to restart.
Review of
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the EDG and support systems' IBIRs verified that outstanding
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mechanical maintenance associated with the EDGs was appropriately prioritized and scheduled.
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Conclusion
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Overall, the inspectors concluded that outstanding safety related i
electrical maintenance and EDG mechanical maintenance had been i
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i appropriately prioritized and scheduled.
Based on the assumption
that currently scheduled maintenance would be accomplished, all j
i electrical maintenance will be completed which would impact Unit 2 j
l operation prior to restart. The PN-30 methodology for this i
process was appropriately implemented. The electrical system engineers were knowledgeable of the process, their system's equipment, and the status of outstanding maintenance. The system engineers demonstrated a thorough involvement in the maintenance activity associated with their system.
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Onsite Follow-up of Licensee Written Reports (IP 92700): LER 92-017 and Restart Item B-1
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This issue was reviewed by the NRC in a previous inspection (NRC Report No. 50-325,324\\93-11), however the licensee's corrective actions were not c'amplete with respect to the 4.16 kV breakers and their association with this LER and Unit 2 restart.
LER 92-017 documented a safety related breaker failure, due to lubrication hardening, on an ABB 480 V breaker on one of Brunswick's emergency buses E-5 through E-8.
The emergency buses' 4.16 kV breakers on buses E-1 through E-4 at the station were ABB 5 HK breakers. The ABB 5 HK breaker had experienced this failure mechanism at another nuclear plant. A potential challenge to the reliability of 4.16 kV breakers on emergency buses E-1 through E-4 was not sufficiently evaluated and resolved. The specific concern was whether these breakers should be refurbished prior to restart rather than after restart.
During this inspection the licensee provided a letter from the vendor, ABB, which addressed this concern.
The ABB letter to Mr. G. Miller of CP&L, dated March 8, 1993, stated that six of these Brunswick breakers had been disassembled and inspected by the vendor. No significant wear or lubrication concerns were identified. Additionally, the licensee verified that breaker PMs had been accomplished within the last three years and there was no history of lubrication related failures on these breakers at Brunswick. The vendor conclusion based on this information was that there was no sufficient reason to delay plant start-up due to this concern. The refurbishment schedule will complete refurbishment of the safety related breakers by December, 1994.
Restart item B-1 remains open pending NRC management review of the 4.16 kV safety related breaker refurbishment schedule and justification for delaying refurbishment until after Unit 2 restart. This information was requested in transmittal letter of NRC Report No. 50-325,324/93-11.
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LER 92-017 will remain open pending a revision of the LER by the licensee. The revision will address corrective action item number 7 to clarify the actions accomplished to resolve breaker concerns with the 4.16 kV breakers. The originally stated action indicated all safety related breakers would be inspected; the action accomplished was to inspect a sample of breakers and assess the lubrication hardening potential to these breakers.
During the review of the 4.16 kV breaker vendor manual (0-FP-3738) the inspectors noted that an ABB vendor manual update (MS 3.2.1.9-1D) was not received by the plant via the defined vendor interface. The revision was received by an engineer visiting the vendor manufacturing location. The inspectors verified that a program was established for the licensee to receive and distribute vendor updates. Vendor manual interface deficiencies had previously been identified by the licensee in ACR 92-421, initiated in June, 1992. A three year program was initiated in December,1992 to update plant vendor manuals. The licensee
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indicated that the ABB vendor manual reviewed by the inspectors, 0-FP-3738, had not yet been addressed by the enhancement program. The inspectors concluded that' this deficiency had been previously identified by the licensee and corrective actions were being implemented.
4.
IN 89-29, Potential Failure of Asea Brown Boveri circuit Breakers During Seismic Event The inspectors reviewed the applicability of NRC IN 89-29, " Potential Failure of Asea Brown Boveri Circuit Breakers During Seismic Event" to Brunswick. The IN indicated that ABB K-line Circuit Breaker models K225 through K2000 manufactured prior to July,1974 had slow close levers which could move during a seismic event and prevent the breaker from closing upon an electrical demand. ABB added a spring to the breaker design which prevented vibration induced movement of the slow close latch. All ABB K-line breakers manufactured since mid 1974 have this
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spring installed.
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The licensee determined that the IN was applicable to Brunswick. The affected breakers were the 480 V bus E-5, E-6, E-7 and E-8 bus tie breakers. These four electrically operated K1600 breakers were within the scope of IN 89-29. Modification 91-030 added the slow close lever springs to these four breakers. The inspectors examined the four bus tie breakers and verified that the slow close lever springs were installed. The licensee's response to IN 89-29 was considered appropriate.
5.
Westinghouse MCCB Failure Mechanism The licensee identified a failure mechanism on Westinghouse 4B0 V MCCBs, types HMCP and HFD. The licensee initiated an investigation of these breakers in December,1992 following the identification of a failure trend in this equipment. A root cause evaluation identified the failure cause to be a manufacturing defect. A material change in the magnetic trip coil plunger of the HMCP breaker introduced a structural defect.
The lubricant used during manufacture of both breaker types was also changed. The result was inadequate lubrication at critical hinges on both breaker types.
There were 139 HMCP and 79 HFD type breakers installed in safety related applications at Brunswick.
The inspectors reviewed the licensee's corrective actions for this electrical equipment deficiency. The licensee submitted an initial Part 21 notification on February 25, 1993. Actions were initiated to replace i
all 73 HMCP breakers on Unit 2 prior to start up. At the date of this
inspection, 44 had been replaced. During field walkdowns the inspectors verified replacement of these breakers. The HFD breakers were to be i
individually tested for indications of failure. Breakers would be replaced if the test revealed slow tripping or sticking breakers. A total of 48 WR\\J0s were initiated to accomplish testing on the Unit 2 HFD breakers. Those breakers which would not be tested, such as weld receptacle breakers, would be tagged ope.
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I The MCCB control handle and contact operating mechanism move jointly, therefore control handle movement was used as the basis for assessing proper breaker function. The HFD type MCCBs were cycled to close and
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then tripped via the manual trip.
Some MCCBs exhibited obvious sluggish control handle trip response due to the increased internal friction from i
lack of lubrication.
In some instances the MCCB mechanism operated yet the handle and breaker contacts did not fully travel to the tripped position. This was the failure mechanism described in the part 21 notification.
The licensee's corrective action was controlled by EER 93-0272.
Individual WR/Jos were written to manually trip test each safety related type HFD breaker. Spare HFD breakers in warehouse stock were also manually and electrically trip tested. All breakers were manually trip tested 10 times and sluggish operation constituted failure requiring replacement. No failures occurred on breakers in warehouse stock.
Failures were observed for installed type HFD breakers and the licensee subsequently decided to replace all safety related type HFD breakers.
This activity is scheduled to be completed prior to restart.
The licensee also initiated revisions to PM procedures for these MCCBs to include an annual trip test. The inspectors concluded the licensee had implemented appropriate corrective actions for the Westinghouse MCCB
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deficiency. Completion of these actions will resolve concerns regarding these breakers and Unit 2 restart. The licensee's identification of this equipment deff.1ency demonstrated an example of good problem identification and root cause analysis performance by the technical support organization.
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Exit Meeting The inspection scope and results were summarized on March 12, 1993 with those persons indicated in paragraph 1.
Proprietary information is not contained in the report. The inspector described the areas inspected and discussed in detail the inspection results.
There were no dissenting comments received from the licensee.
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Acronyms and Abbreviations
ABB Asea Brown Boveri
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ACR Adverse Condition Report EDG Emergency Diesel Generator EER Engineering Evaluation Report EWR Engineering Work Request
I&C Instrumentation and Controls l
IBIR Integrated Backlog Item Report
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IN Information Notice kV kilovolt LER Licensee Event Report
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j MCC Motor Control Center HCCB Molded Case Circuit Breaker
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PM Preventive Maintenance VAC Volts Alternating Current VDC Volts Direct Current I
WR/JO Work Request / Job Order j
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