IR 05000327/1993026
| ML20056D128 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/21/1993 |
| From: | George Macdonald, Shymlock M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20056D125 | List: |
| References | |
| 50-327-93-26, 50-328-93-26, NUDOCS 9308050019 | |
| Download: ML20056D128 (12) | |
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(MITED STATES
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-'k NUCLEAR REGULATORY COMMISSION REGION 81
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101 MAR!ETTA STREET, N.W, SUITE 2900
- y ATLANTA GEORGIA 303234199
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Report Nos.: 50-327/93-26 and 50-328/93-26 Licensee:
Tennessee Valley Authority 6N 38A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Docket Nos.:
50-327 and 50-328 License Nos.: DPR-77 and DPR-79 Facility Name:
Sequoyah Units 1 and 2 Inspection Conducted:
June 14 - 25, 1993 Inspector: /
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'/ p GI MacDonald Date Signed
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Approved by
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,+ M/ B;/Shymlock, Section Chief Date Signed
, Engineering Branch
' Division of Reactor Safety SUMMARY Scope:
This special announced inspection was performed to assess the licensee's balance of plant (B0P) equipment and systems. The inspection evaluated the licensee's corrective actions taken in response to equipment problems that contributed to unplanned transients and challenges to reactor safety systems.
System walkdowns were performed to assess the material condition of selected B0P systems prior to plant restart. The following systems were reviewed:
main feedwater control, main generator, switchyard and transformers, 6900 volt electrical distribution, 480 volt electrical distribution, and low voltage electrical distribution.
Some of the systems chosen for review contained both safety related and non-safety related equipment.
Results:
In the areas inspected, violations or deviations were not identified. A concern was raised on the wiring of replacement current transformers. The licensee will verify that all replacement current transformers are properly installed prior to restart of either unit.
(Para. 5.)
9308050019 930721 PDR ADOCK 05000327 O
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There was concern regarding the Arrowhart Motor Control Centers. The Arrowhart motor control centers were obsolete and the Arrowhart motor starter auxiliary control switch had demonstrated poor reliability. The licensee will
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inspect all safety related and unit reliability related Arrowhart motor starters prior to restart.
(Para. 6.)
Licensee system engineers were cognizant of system backlog and work status and generally made conservative decisions regarding prioritization of work items
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for restart.
A considerable amount of major maintenance was complete and remained scheduled for restart on the electrical systems which should improve
electrical distribution system reliability.
Some existing work backlog identified and tracked by the TVA Customer Group i
which consisted of past due relay calibrations and switchyard equipment preventive maintenance, did not appear to have been evaluated by the backlog review process. This was considered a weakness in the backlog review process.
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Some system equipment deficiencies were noted by the inspector during system walkdowns and were identified to the system engineers and licensee management.
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Several cf the discrepancies had not previously been identified by the licensee, however, the system engineers had not yet started their system walkdowns for restart. These items identified by the inspectors were not considered to be restart items.
This balance of plant system review is not complete.
Additional review of work status and system walkdowns are scheduled prior to Sequoyah restart.
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e REPORT DETAILS 1.
Persons Contacted Licensee Employees
- J. Baumstark, Operations Manager
- M. Cooper, Sequoyah Restart Management
- R. Drake, Project Management and Controls Manager
- R. Driscoll, Site Quality Manager
- R. Eytchison, Vice President Nuclear Operations
- R. Fenech, Vice President Sequoyah
- T. Flippo, Program Manager
- J. Gates, Outage Manager
- R. Goodman, Technical Training Manager
- D. Lundy, Technical Support Manager
- K. Meade, Licensing Engineer
- T. Nahay, Sequoyah Restart Management
- S. Poage, Nuclear Assurance Audit and Assessment Manager
- D. Stephens, Sequoyah Customer Group Manager
- R. Thompson, Compliance Licensing Manager
- P. Trudel, Manager Design Engineering
- J. Ward, Manager Engineering and Modifications Other licensee employees contacted during this inspection included engineers and administrative personnel.
Other organizations NRC Personnel
- W. Holland, Senior Resident Inspector (Sequoyah)
- C. Hughey, Resident Inspector (Region II)
- W. Poertner, Resident Inspector (Region II)
- M. Thomas, Regional Inspector
- Denotes those individuals that attended the exit meeting.
Acronyms and abbreviations used throughout this report are listed in the last paragraph.
2.
Main Feedwater Control System (System 46)
The inspector reviewed the Main Feedwater system description provided in the UFSAR section 10.4.7.
The licensee's Plant Reliability Study and two third party evaluations of secondary plant performance were reviewed to determine the reliability significant system problems identified during these studies.
The inspector then reviewed the backlog review notebook for the main feedwater control system to determine if the reliability significant system problems were addressed by the existing backlog of identified work for the syste _-
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The backlog of identified work for system 46 consisted of open work requests and work orders, conditions adverse to quality, master issues list items, design change notices, and obsolete equipment items.
Fifty one total items were identified for system 46, and thirty six were classified as restart items.
The function of the Main Feedwater Control System was to provide a i
signal to control MFPT speed in response to inputs from feedwater and
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steam header pressures and steam flow inputs from all 4 steam generators.
The inspector reviewed the system operational problems and corrective actions completed or in the restart list.
System 46 operational
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problems were-i e
In 1992 a Potter Brumfield K1 relay failed to operate in the Foxboro 62H controller of the No. 3 feedwater regulating valve of Unit I which resulted in a unit trip.
The problem was determined to be increased relay contact resistance. Relay replacement with
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an alternate relay is a restart item for Unit 1.
Due to parts availability relay replacement was not a restart item for Unit 2.
i The Unit 2 relays were scheduled for contact cleaning or
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replacement with another Potter Brumfield relay prior to restart.
e Several MFP operational problems have occurred due to inadvertent spray down of the MFPs and controls by the fire protection system.
A modification was listed as a restart item to correct this problem.
e On February 5, 1993 and February 18, 1993, the MFPT 1B governor valve failed to close following a reactor trip. This has been corrected on MFPT 1B. The problem was determined to ba gearbox binding and limit switch calibration. MFPT 1A and 2A have not exhibited the problem.
MFPT 2B has shown symptoms of this problem and was scheduled for maintenance prior to restart.
Major activities completed or scheduled as restart items for the system consisted of replacement of solenoids for the HP and LP stop valves for all MFPTs, HP and LP stop valve limit switch repairs, repairs to governor valve positioners and indicator lights, repairs to drain valve limit switches and indicator lights, pressure controller calibration, oil cleaning, and various oil leak repairs. The present Foxboro 62H
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controllers were obsolete and alternatives were being considered as post restart items.
The inspector performed a preliminary walkdown of the system to ensure that significant problems had been identified in the restart list and to l
verify an acceptable material condition existed prior to plant restart.
The MFPT controls located at each MFPT were inspected. At the time of
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the inspection the main feedwater control system was secured and the oil i
pumps were not running. A bolt was missing from the mounting plate for
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Unit 2A MFPT condenser.
Several oil / pneumatic line clamps were loose and one pipe support was missing the pipe clamps.
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From the review of outstanding work / design items and the preliminary system walkdowns, the inspector considered that appropriate work items
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Main Generator Electrical (System.57)
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l The inspector reviewed the Main Generator system description provided in I
the UFSAR section 10.2.
The licensee's Plant Reliability Study and two
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third party evaluations of secondary plant performance were reviewed to determine the reliability significant system problems identified during
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these studies. The inspector then reviewed the backlog review notebook for the main generator system to determine if the reliability significant system problems were addressed by the existing backlog of identified work for the system.
The backlog of identified work for system 57 consisted of open work requests and work orders, master issues list items, design change I
notices, operator aides,and obsolete equipment items.
Forty four total items were identified for system 57, and thirty one were classified as restart items.
The main generator system consisted of the generator, exciter, voltage regulator and associated protective circuits and monitoring instrumentation.
The inspector reviewed the system operational problems and corrective actions completed or in the restart list. The plant reliability study
identified two plant transients caused by system 57 equipment failures.
In November 1988 a ground fault occurred on stator phase C of the Unit 1
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generator. The Unit 1 generator was subsequently rewound eliminating the i
ground problem. Unit 1 generator tripped in June, 1990 due to inadvertent actuation of the 100% ground fault relay 159GN3. Relay setting changes were scheduled as restart items to change the relay pickup to correct the prGblem.
Restart items scheduled for system 57 included minor repairs to hydrogen coolers, replacement of exciter cooling water piping, extensive cleaning and testing of the automatic voltage regulators, and various repairs to main generator monitoring instrumentation.
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The inspector-performed a preliminary walkdown of the system to ensure that significant problems had been identified in the restart list and to verify an acceptable material condition existed prior to plant restart.
The Unit 2 generator disconnect links had been removed and the inspector noted that garbage had been left insise the disconnect links.
j From the review of outstanding work / design items and the preliminary
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system walkdowns, the inspector considered that appropriate work items were scheduled to be completed prior to restart.
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4.
Transformers and Switchyard (System 241)
The inspector reviewed the Transformers and Switchyard description l
provided in the UFSAR section 8.1 and 8.2.
The licensee's Plant
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Reliability Study and two third party evaluation * of secondary plant
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performance were reviewed to determine the rel' o tity significant l
system problems identified during these studie... The inspector then reviewed the backlog review notebook for system 241 to determine if the
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reliability significant system problems were addressed by the existing backlog of identified work for the system.
The inspector reviewed the TVA customer group work tracking systems and i
noted that some customer group work activities were not reviewed as part-of the backlog review process.
The protective relay calibrations and certain customer group switchyard routine testing and routine preventive maintenance activities were not included in the backlog. The licensee indicated that these work activities will be reviewed under the backlog review process. This was considered a program weakness.
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The backlog of identified work for system 241 consisted of open work requests and work orders, conditions adverse to quality, master issues list items, design change notices, and obsolete equipment items. Of the i
112 total items identified for system 241, 71 were classified as restart j
items.
System 241 consisted of the main transformers, unit auxiliary transformers, common station service transformers, the'161 kV switchytrd i
components, the 500 kV switchyard components, and monitoring and protective instrumentation.
The plant reliaoility study identified several plant transients initiated by system 241 equipment failures. A dual unit trip resulted from a breaker failure caused by incorrect breaker timing testing.
Corrective actions for this failure had been addressed. Several plant trips had been attributed to failures of transformer gas sensing relays.
A transformer fire occurred due to incorrect transformer bushing belleville washer installation. The transformer belleville washer and gas sensing relays were scheduled as restart items. The licensee had begun a program to use thermography on switchyard equipment to locate impending problems.
Common station service transformer (CSST) A automatic load tap changer had a high number of. operating cycles (approximately 240,000). The vendor manual recommended an inspection of the load tap changer when the operating cycles reached 200,000 cycles. This item was not scheduled as a restart item.
The inspector performed a preliminary walkdown of the system to ensure j
that significant problems had been identified in the restart list and to j
verify an acceptable material condition existed prior to plant restart.
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In the 500 kV switchyard the inspector noted that the ground mat was
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f exposed in many locations. A cracked air compressor drive belt was noted on compressor B of PCB 5054.
In the 161 kV switchyard, an air leak was noted in the air control cabinet of PCB 908. Oil leaks were developing in PCB 918 and PCB 984. Nine of the total eighteen 161 kV
circuit breaker air compressors were due for their annual compressor i
maintenance.
The licensee was extending the major maintenance overhaul
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frequency for the 161 kV circuit breakers from 9 years to 12 years. One
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of the two Unit 2 main generator breakers was presently due for its 9 year major maintenance and it was being deferred for an additional three
years.
From the review of outstanding work / design items and the preliminary
system walkdowns, the inspector considered that all system 241 backlog
items had not been reviewed. The licensee indicated that they will t
review the customer group protective relay backlog, the customer group switchyard routine testing and preventive maintenance backlogs using the backlog review process to determine if additional items require work
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prior to restart.
Further followup of these system 241 issues will be performed on subsequent inspections prior to restart.
5.
6900 Volt Electrical Distribution System (System 202)
The inspector reviewed the 6900 Volt EDS description provided in the UFSAR sections 8.2 and 8.3.
The licensee's Plant Reliability Study and two third party evaluations of secondary plant performance were reviewed to determine the reliability significant system problems identified i
during these studies. The inspector then reviewed the backlog review
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notebook for system 202 to determine if the reliability significant system problems were addressed by the existing backlog of identified work for the system.
The backlog of identified work for system 202 consisted of open work requests and work orders, conditions adverse to quality, master issues list items, design change notices, justification for continued operation and obsolete equipment items. Of :.ne 123 total items identified for i
system 202, 98 were classified as restart items.
System 202 consisted of the 6900 volt start boards, unit boards, shutdown boards, common boards and cooling tower boards.
System 202 operational problems included:
cracked current transformers in Asea Brown Boveri (ABB) 7.5 HK and o
15 HK switchgear.
- Sticking trip pushbuttons on the 7.5 HK switchgear. The trip pushbutton was being worked as a restart item.
- An incorrectly installed CT in start bus breaker 1614 led to an inadvertent trip of breaker 1614 and an unplanned challenge to safety systems. All four EDGs started and EDG IB-B energized its shutdown bus.
The licensee performed an incident investigation of i
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the incorrectly installed CT. The replacement CT secondary
terminals were reversed from the original cts. The XI and X2
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markings were not on the same side of the CT. Failure to follow
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procedures in the lifting and landing of these CT secondary leads caused the CT to be wired incorrectly and led to the trip of the i
breaker. The CT was replaced in November, 1992 when the CT was l
found to contain a crack. The licensee was performing CT l
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inspections due to a notice from the vendor on CT cracking.
The work package which replaced the CT did not specify adequate post
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maintenar.ce testing (PMT) to identify the incorrectly wired CT.
l Only a megger test was specified as PMT for the CT replacement.
The 1614 breaker is an alternate feeder to start bus lA and was
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never aligned as normal feeder to the start bus until recently.
Once the 1614 breaker was aligned as the normal feeder it did not experience enough load until the attempted start of an RCP motor which caused it to trip. The licensee will verify that all replacement cts are properly installed prior to restart. The inspector will follow this item during subsequent inspections prior to restart.
This event was very similar to an incident which occurred on December 19, 1991. During the December 19, 1991 incident an incorrectly installed current transformer led to a trip of the main generator. This indicates that previous
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corrective actions for the December 19, 1991 event was inadequate l
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A maintenance concern existed on the shutdown board normal feeder l
due to a reduced undervoltage protection when aligned to the
alternate feeder. An additional 80% undervoltage relay was scheduled to be added to the shutdown boards as a restart item to address this concern.
- A design concern existed on the overduty of the unit boards. This will be corrected with the new alignment of preferred power from the CSSTs. This was not a restart item.
- A concern was identified with CSST C start bus feeder cables.
Under certain conditions the cables could exceed their 90 degrees Centigrade temperature rating. A JC0 was in place to provide i
administrative controls to preclude operating under conditions which would cause high cable temperatures.
This item was
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Major restart work activities included implementing the start e
board fast transfer scheme, board outages for the start boards, turbine building common boards and shutdown boards, breaker maintenance, and installation of the shutdown board 80%
undervoltage relays.
The inspector performed a preliminary walkdown of the system to ensure that significant problems had been identified in the restart list and to verify an acceptable material condition existed prior to plant restart, i
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The unit boards, start boards, shutdown boards, and turbine building common boards were inspected. The material condition was generally acceptable, the inspector noted two leaking blocking diodes in two compartments of unit board 2C.
From the review of outstanding work / design items and the preliminary system walkdowns, the inspector considered that appropriate work items were scheduled to be completed prior to restart.
6.
480 Volt Electrical Distribution System (System 201)
The inspector reviewed the 480 volt EDS description provided in the UFSAR section 8.3.
The licensee's Plant Reliability Study and two third party evaluations of secondary plant performance were reviewed to determine the reliability significant system problems identified during these studies. The inspector then reviewed the backlog review notebook for system 201 to determine if the reliability significant system problems were addressed by the existing backlog of identified work for the system.
The backlog of identified work for system 201 consisted of open work requests and work orders, conditions adverse to quality, master issues list items, design change notices, and obsolete equipment items. Of the
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103 total items identified for system 201, 44 were classified as restart items.
The system consisted of the safety related and the non-safety related 480 volt boards and motor control centers (MCCs).
The plant reliability study did not identify any plant trips attributable to system 201
equipment.
The major operational problem with system 201 included the following:
The Arrowhart and Allis Chalmers motor starters were obsolete.
The Arrowhart motor starter auxiliary switch contacts have exhibited poor reliability. The licensee had a PER to inspect all safety related and unit reliability related Arrowhart motor starter auxiliary switch contacts prior to restart. A 10 % sample
of the remaining Arrowhart motor starter auxiliary switch contacts will be inspected prior to restart.
- There was a design concern identified in the BOP 480 volt Westinghouse DS switchgear. No selective coordination existed in the 480 volt B0P Westinghouse due to a-discriminator circuit installed in the Amptector trip units of the feeder breakers. A modification had been performed to bypass the discriminator instantaneous trip feature for the safety related feeder breakers. The modification for the B0P equipment was scheduled as a non-restart item.
- Alterr; ate feeder circuits to boards and MCCs were not qualified.
This was restrictive on maintenance to the equipment.
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Major restart activities for system 201 included board outages for many
480 volt boards and MCCs, and the Arrowhart motor starter inspections.
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The inspector performed a preliminary walkdown of the system to ensure
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that significant problems had been identified in the restart list and to l
verify an acceptable material condition existed prior to plant restart.
Several 480 volt shutdown boards, unit boards, common boards, and motor l
control centers were inspected. The general condition of the equipment i
was acceptable. The breaker closed indicator light socket in l
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compartment 9 of the 480 Auxiliary Building Common Board was broken. On 480 volt Reactor M0V Board 18-1B the inspector noted motor starter l
auxiliary contacts in poor condition on MOV l-FCV-3-100.
Turbine l
Building Vent Board MCC 2B, compartment 2C had a noisy starter coil.
Work requests were initiated for these deficiencies. These items had
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not been previously identified by the licensee.
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From the review of outstanding work / design items and the preliminary I
system walkdowns, the inspector considered that appropriate work items I
were scheduled to be completed prior to restart.
7.
Low Voltage AC and DC Distribution System (System 250)
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The inspector reviewed the Low Voltage AC and DC Distribution System i
description provided in the UFSAR section 8.3.
The licensee's Plant
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Reliability Study and two third party evaluations of secondary plant
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performance were reviewed to determine the reliability significant
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system problems identified during these studies.
The inspector then reviewed the backlog review notebook for system 250 to determine if the reliability significant system problems were addressed by the existing
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backlog of identified work for the system.
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System 250 consisted of the vital 125 VDC batteries, battery chargers, inverters, and the 250 VDC station batteries, battery chargers, and inverters.
The backlog of identified work for system 250 consisted of open work requests and work orders, conditions adverse to quality, master issues list items, design change notices, and obsolete equipment items. Of the 81 total items identified for system 250, 35 were classified as restart i
items.
The plant reliability study identified one plant transient caused by a failure of system 250 equipment. A faulty vital inverter transfer j
switch had caused one unplanned plant transient.
Replacement of vital inverter transfer switches was identified as a restart item. The plant station batteries were aging. They were nearing their 20 year life.
Plans for replacement were being made however this was not a restart item.
Plant vital batteries were also approaching their replacement interval.
Battery replacement was not a restart item. Current battery capacity test results were still acceptable.
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The inspector performed a preliminary walkdown of the system to ensure that significant problems had been identified in the restart list and to verify an acceptable material condition existed prior to plant restart.
All the vital batteries and station batteries were inspected.
Selected battery chargers, inverters, battery boards and 120 VAC vital power
boards were inspected. On station battery 1, the inspector noted a damaged intercell cable connector.between cells 60 and 61. A work request was written to repair the deficiency.
In the station battery room the inspector noted water seepage into the room which was coming up through the battery room floor.
The leakage appeared to be very slight, however the water collecting in the vicinity of the battery racks posed a personnel safety hazard to workers.
In the adjacent battery board room, water inleakage was also noted in the room and inside of 250 VDC battery board compartment 1, the battery board normal feeder breaker.
This provided a potential for grounding. There was no ground present on the battery board.
The inspector noted that approximately 20 spare battery cells for the station batteries were being stored in the Lawson Building adjacent to the 161 kV switchyard. The battery cells were being kept on a trickle charge of 2 to 3 amps. The room was also being used for storage of
surplus electrical equipment. There was so much surplus equipment located in the room that access to the fire extinguisher was blocked.
This was a potential fire hazard. The licensee fire protection group had identified the condition and issued a notice to electrical maintenance and the problem was corrected.
From the review of outstanding work / design items and the preliminary system walkdowns, the inspector considered that appropriate work items were scheduled to be completed prior to restart.
8.
Exit Interview The inspection scope and results were summarized on June 25, 1993, with those persons indicated in paragraph 1.
The inspector described the areas inspected and discussed in detail the inspection findings.
Dissenting comments were not received from the licensee.
Proprietary information is not contained in this report.
5.
Acronyms and Abbreviations ABB Asea Brown Boveri AC Alternating Current B0P Balance of Plant CSST Common Station Service Transformer CT Current Transformer DC Direct Current EDG Emergency Diesel Generator EDS Electrical Distribution System FCV Flow Control Valve J
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JC0 Justification for Continued Operation kV Kilovolt
MCC Motor Control Center
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HFPT Main Feedwater Pump Turbine
MOV Motor Operated Valve NRC Nuclear Regulatory Commission
PCB Power Circuit Breaker l
PER Problem Evaluation Report i
PMT Post Maintenance Test TVA Tennessee Valley Authority UFSAR Updated Final Safety Analysis Report VAC Volts Alternating Current VDC Volts Direct Current
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