IR 05000395/1989022
| ML20005E424 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 12/20/1989 |
| From: | Cantrell F, Modenos L, Prevatte R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20005E423 | List: |
| References | |
| 50-395-89-22, NUDOCS 9001050215 | |
| Download: ML20005E424 (23) | |
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_ NUCLEAR REGULATORY COMMISSION -
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UNITED STATES
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101 MARIETTA STREET.N.W.
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ATLANTA.GEoRot A 30323 -
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= Report N'o,:~ 50-395/89-22'
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Licensee: South Carolina Elect'ric & Gas Company
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Columbia, SC 29218 f
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Docket No.:
50-395 License No.: NPF-12 f*
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L Facility Name:. V.,CDSummer t
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Inspection Conducted:
November 1 - 30, 1989 Inspectors:
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IE'3C' O ichard L.-Prevatte Date-Signed M /I
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go.feoP.Modenos Date Signed
'Approv'ed by:
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- Flfy( S. Cantrell, Seffionf)tief
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. Division.of Reactor Pf ojet't's SulEARY
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-Scope:.
' This routine -inspection was conducted by the resident inspectors onsite in the
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areas of monthly surveillance observations, rc.athly maintenance observation,
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operational safety verification, onsite follow-up of events and subsequent
written reports, cold weather preparation, installation and testing of modifi-
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L cations, and.other areas.
Selected tours were conducted-on backshift or
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weekends.
Backshift or weekend tours were conducted on 15 days during this l
inspection period.
Results:
The unit was operated at 100 percent power throughout the reporting period.
No major deficiencies were identified in the areas of surveillance and operational safety verification (paragraphs 2 and 4).
In the area of maintenance, an IFI which requires a revision of MOVATS procedures was identified (paragraph 3b).
r The licensee also identified a failure to follow prc::edures while retesting a i
chiller pump after repair.
This item will be tracked as a NCV (paragraph Sc).
In the area of onsite follow-up of events (paragraph 5), the licensee identified that an inadequate procedure had resulted in the failure to verify that an 9001050215 891220 PDR ADOCM 05000395
PNV
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alarm would be received in the control room under all low flow conditions on the mW plant vent and reactor building purge radiation monitors.
This item will Law be tracked as a NCV.
The inspectors independently verified that the licensee had completed the necessary preparations for extreme cold weather (paragraph 7).. The inspectors commenced inspection on the installation and testing of recent modifications.
The design and work activities completed to date for modification to provide biecide treatment of the service water system (MRF 20629) were reviewed (paragraph 6).
The inspectors performed a review to verify the licensee's quality assurance program implementation (paragraph 8).
The inspectors reviewed the licensee's implementation of the installation of a non-safety grade battery charger to be used for occasional equalization charging of a limited number of battery cells of the station battery banks.
A safety evaluation which includes recommendations for use of this single cell charger is attached (paragraph 9).
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h, REPORT DETAILS 1.
Persons Contacted Licensee Employees
- W. Baehr, Manager, Chemistry and Health Physics
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C. Bowman, Manager, Scheduling and Modifications 0. Bradham, Vice President, Nuclear Operations M. Browne, Manager, Systems Eagineering & Performance W. Higgins, Supervisor, Regulatory Compliance
- S. Hunt, Manager, Quality Systerts
- A. Koon, Manager, Nuclear Licensing G. Moffatt, Man 6ger, Maintenance Services
- D. Moore, General Manager, Engineering Services
- K. Nettles, General Manager, Nuclear Safety
- C, Price, Manager, Technical Oversite M. Quinton, General Manager, Station Support J. Shepp, Associate Manager, Operations
- J. SKolds, General Manager, Nuclear Plant Operations
- G. Soult, General Manager, Operations and Maintenance G. Taylor, Manager, Operations D. Warner, Manager, Core Engineering and Nuclear Computer Services M. Williams, General Manager, Administrative & Support Services K. Woodward, Manager. Nuclear Operations Education and Training Other licensee employees contacted included engineers, technicians, operators, mechanics, security force memberst and office personnel.
- Attended exit interview Acronyms and initialisms used throughout this report are listed in the last paragraph.
2.
Monthly Surveillance Observation (61726)
The inspectors observed surveillance activities of safety related systems
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and components to ascertain that these activities were conducted in t -
becordance with license requirements.
The inspectors observed portions of i
seven selected surveillance tests including all aspects of the Solid State l
Protection System Actuation Logic and Master Relay Test foi frain B, STP i
345.074.
The inspectors verified that required administrative approvals were obtained prior to initiating the test, testing was accomplished by l
qualified personnel, required test instrumentation was properly calibrated, data met TS requirements, test discrepancies were rectified, and the systems were properly returned to service.
No major discrepancies were identified while observing the above surveillance test.
However, the licensee discovered a problem relating to an inadequate surveillance test procedure that was used to calibrate the flow switches and low +1ow alarms for the radiation atmospheric monitors.
This item is discussed in detail in paragraph Sb and in LER 89-18.
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No violations or deviations were identified.
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3.
Monthly Maintenance Observation (62703)
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The inspectors observed maintenance activities of safety related systems and components to ascertain that these activities were
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conducted in accordance with approved procedures, TS, industry codes and standards..The inspectors determined that the procedures used
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were adequate to control the activity, and that.these activities were accomplished by qualified personnel.
The inspectors independently verified that the equipment was properly tested before being returned
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to service.
Additionally, the inspectors reviewed several
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outstanding job orders to determine that the licensee was giving L
priority to safety related maintenance and not developing a backlog which might affect a given system's performance.
The following
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specific maintenance activities were observed:
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PMTS P0124839 Sample oil and analyze oil sample - change oil
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and oil filter on main generator circuit breaker,
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air compressor
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MWR 8910348 Adjust sample flow differential pressure switches
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on RMA4 per NCN 3489 i
MWR -8910347 Adjust sample flow differential pressure switches l
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on RMA3 per NCN 3489
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PMTS P0128183 Change MOV rotor contacts for valve position indication from rotor 2 to rotor 4 on XVG 3005B-0-SP PMTS P0128187 Change MCV rotor contacts for valve position
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indication from rotor 2 to rotor 4 on XVG
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3001B-0-SP
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MWR 8901923 Repair DG B air start compressor relief valve
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MWR 206290008 Prepare and install concrete pad and protective posts for MRF-20629 PMTS P0127777 Visual inspection of freeze protection and heat tracing i
MWR 89M0387 Replace bearings and adjust belt on ventilation fan for IDA switchgear room MWR 89E0156 Replace motor bearing on XFN0050-M for IDA
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PMTS P0127795 Perform 18 month CC system temperature / flow
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tests
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No major discrepancies were identified during the above observations.
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Some minor discrepancies were identified.
These were discussed with E
the immediate job supervisors and corrective actions were taken to
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correct the deficiencies and prevent recurrence.
Overall, the
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technicians and mechanics performing each job appeared to be well
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trained and knowledgeable on all aspects of each assigned task, b.
On November 9,1989, the inspector accompanied an electrician and his-supervisor to witness EMP 445.007. H0 VATS Testing of Limitorque
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Valves, on the C SWIV.
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In order to perform this test, the electrician needed to ' bypass
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certain electrical interlocks for automatic valve closure.
This was accomplished by lif ting electrical leads at the MCC, Once this was completed the test proceeded as required.
At the conclusion of the
.ftest.the NRC inspector questioned why there was no QC inspector present to witness the de-termination of the leads to the motor 2,
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control cabinet.
Step 5.2 of procedure EMP 445.007 requires that QC
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witness all de-terminations and reterminations on safety related
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valves.
After questioning by the inspector, the electrician reviewed
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the procedure and realized that a QC inspector was required to be
present.
He stopped all work, located a QC inspector and completed
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the retermination of the wiring leads to the MCC.
Follow-up
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discussions with the electrical supervisors and operations manager
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revealed that the de-terminations and reterminations were conducted as
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per Attachment 1 of SAP-300, Conduct of Maintenance.
The licensee claims that step 5.2 in EMP 445.007 was not necessary and confusing.
Therefore, the licensee is revising procedure EMP 445.007 to
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eliminate any confusion on QC participation.
Until the licensee
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approves the procedure change, this item will be tracked as IFI
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89-22-01, Revise electrical procedure EMP 445.007.
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On September 13, 1989, the licensee vrote an off-normal occurrence for failure to perform post maintenance testing of the chiller water pump B prior to restoring the pump to operable status.
The maintenance
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work was performed on August 21 - 24, 1989.
When the work request was initiated, it stated " Repair and adjust seal leakage", and the
"No" on the retest block was checked off.
In order to complete the work, the pump had to be disassembled and the seal replaced.
The pump was then reassembled and eventually returned to service on September 3, 1989.
On September 13, 1989, the post maintenance reviewer identified that the pump should have been retested in acadance with STP 129.001, HVAC Chilled Water Pump Test.
The test
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was then performed and the pump was returned to operable condition.
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This event occurred due to a generalized job description on the work request and the failure of maintenance personnel to recognize the l
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difference between adjust and repair.
When a pump is disassembled it requires a retest.
There was no safety significance since the pump was proven to be operable and passed the retest.
i The licensee'is currently preparing a LER on this event.
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This LIV is not being cited because the criteria specified in Section
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V.G.1 of the NRC Enforcement Policy were otisfied.
This will be
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tracked as NC4 89-22-02, Failure To Follo.^rocedures for Retest of Chiller Pump.
No violations or deviations were identified.
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4.
Operational Safety Verification (71707)
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The inspectors conducted daily inspections in the following areas:
control room staf fing, access, and operator behavior;. operator adherence to approved procedures, TS, and limiting conditions for
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operations; examination of panels containing instrumentation and other reactor protection system elements to determine that required
channels are operable; and review of control room operator logs, operating orders, plant deviation reports, tagout logs, jumper logs,
and taqs on components to verify compliance with approved procedures.
r The inspectors conducted weekly inspections in the following areas:
verification of operability of selected ESF systems by valve alignment, breaker positions, condition of equipment or component (s),
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and operability of instrumentation and support items essential to i
system actuation or performance.
Plant tours included observation of general plant / equipment conditions, fire protection and preventative measures, control of cctivities in progress, radiation protection controls, physical
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security controls, plant housekeeping conditions / cleanliness, and missile hazards.
The inspectors conducted biweekly inspections in the following areas:
verification review and walkdown of safety related tagout(s) in offect; review of sam 9 ling program (e.g., primary and secondary coolant samples, boric acid tank samples, plant liquid and gaseous samples); observation of control room shift turnover; review of implementation of the plant problem identification system; verification of selected portions of containment isolation lineup (s);
and verification that notices to workers are posted as required by 10 CFR 19.
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Selected tours were conducted on backshifts or weekends.
Inspections included areas in the cable vaults, vital battery rooms, safeguards
areas, emergency switchgear rooms, diesel generator rooms, control
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room, auxiliary building, containment, cable penetration areas, service water intake structure, and other general plant areas.
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Reactor coolant system leak rates were reviewed to ensure that
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detected or suspected leakage from the system was recorded, r
investigated, and evaluated; and that appropriate actions were taken,
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if required.
On a regular basis, RWP's were reviewed and specific i
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l work activities were monitored to assure they were being conducted per the RWP's.
Selected radiation protection instruments were periodically checked, and equipment operability and calibration
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frequency were verified.
In the course of monthly activities, the inspectors included a review of the licensee's physical security program.
The performance of i
various shif ts of-the security force was observed in the conduct of.
daily activities to include:
protected and vital areas access -
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controls; searching of personnel, packages and vehicles; badge
issuance and retrieval; escorting of visitors; and patrols and
compensatory posts, b.
On November 29, 1989, the plant experienced a small transient.
An instrument air line to the heater dump valve 2B ruptured resulting in
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the dump valve failing open on loss of air.
With the valve open the steam from the heater was diverted from the deaerate tank to the condenser.
With the control rods in automatic the reactor power was reduced to approximately 88 percent.
The auxiliary operator ramped the turbine back to compensate for the reduction in the reactor power.
Within ten minutes the dump valve was manually closed and reactor power was returned to 100 percent power.
The cause of the event was copper tubing failure.
The tubing was repaired and the air line was returned to service.
The licensee is continuing to review
this event to determine the root cause of the failure.
No violations or deviations were identified.
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Onsite Follow-up of Events and Subsequent Written Reports (92700,93702)
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The inspectors reviewed the following LER's to ascertain whether the licensee's review, corrective action and report of the identified
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l event or deficiency was in conformance with regulatory requirements, TS, license conditions, and licensee procedures and controls.
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(Closed) LER 87-15, Reactor trip, failure of inverter.
This failure
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resulted from a blown output fuse which caused a los; of power to nuclear instrumentation power range channel (NI-44).
Failure of this l
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i channel resulted in a low low SG level and reactor trip.
Licensee short term corrective action was completed prior to unit restart.
Long term corrective action included a redistribution of loads on channel III to reduce the potential for unit trip on a loss of inverter.
This work was completed under MRF 21316 on October 30, 1989.
MRF 21432 has been approved for testing to verify loading of s
inverters during a ESF actuation.
This work is scheduled for refueling outage No. 5 in 1990.
After this testing is completed, the
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MRF will add an alternate regulated AC power supply to the inverter channels and static transfer switches between the inverter output and the regulated power AC supplies.
This will prevent a loss of power
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to the protection and control cabinets on a loss of the inverter.
It will also provide sufficient fault current throu0h the regulated AC supply to blow the fuses on a short circuit and thereby prevent this inverter fror. locking up on current limit.
This installation is
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scheduled to be completed during refueling outage No. 6 in late 1991 or early 1992.
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(Closed) LER 88-014, Two pressurizer safety valves inoperable, places plant in TS 3.0.3.
This event was reported by the licensee in a letter dated January 19, 1989.
It was the result of the licensee testing two safety valves and finding them outside the allowable limit of 2485 psig +/- 1 percent lif t setting pressure.
This event occurred while the plant was in Mode 3.
The valves had their set point adjusted and were returned to an operable status within three hours.
To provent recurrence, a change was made to the surveillance procedure STP 401.001 that will allow testing of only one safety valve at a time.
This should prevent having more than one safety valve inoperable at a time.
b.
On October 27, 1989 the licensee identified that the control room did not receive a low flow alarm when the sample pumps on radiation monitors for the main plant vent (RM-A3) and the reactor building purge system (RM-A4) were stopped.
An investigation by the licensee revealed that a low flow alarm was operable, but was only received when a high differential pressure condition was sensed across installed filters.
This signal relates to a clogged filter.
The design of the system also provides a differential pressure switch
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that can be set to detect low differential pressure across the filter.
This signal relates to a low flow condition.
The low l
differential pressure switch for low flow was not addressed in the
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licensee's STP 360.036, used to perform this ACOT on this equipment.
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The surveillance for RM-A3 and RM-A4 specified in TS 4.3-9 notes (1)
3 and (2) 3 requires the AC01 verify operation of the low flow alarm
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STP 360.036 did not contain steps to verify j
this low flow alarm condition.
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Upon discovery of this deficiency, the licensee declared RM-A3 and RM-A4 inoperable, entered the TS action statement and used alternate means to verify system flow.
The calibration and ACOT procedures were revised to address both the high and low flow differential pressure switches.
The switches were set and successfully tested on November 10, 1989.
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f This event occurred due to an inadequate procedure.
The safety significance was minimal since both radiation monitors are non-safety related installations that provide a _ backup for administrative 1y controlled releases from the waste gas decay tanks and the reactor building purge system.
RM-A3 is additionally backed up by RM-A10.
The licensee is currently preparing a modification, MRF 2781, which will enhance the overall operation of this system.
They are additionally preparing a LER 89-18 on this event.
This LIV is not being cited because the criteria specified in Section V.G.1 of the NRC Enforcement Policy was satisfied.
This will be tracked as NC5 89-22-03, Inadequate STP for Radiation Monitors.
No violations or deviations were identified.
6.
Installation and Testing of Modifications (37828)
The inspectors started a review of recently performed plant modifications to ascertain that activities which are not submitted for approval to the NRC are in conformance with the requirements of the TS,10 CFR 50.59 and 10 CFR Part 50, Appendix B, Criteria III, Design Control.
MRF-20629, Service Water System Biocide Treatment, is being reviewed and work has been observed to assure that it is being performed in accordance with approved instructions, procedures and drawings.
The modification has been submitted to the South Carolina Department of Health and Environmental Control and has received approval to treat the service water system with Betz "CT-1" to control Asiatic clams and microbiological 1y induced corrosion.
The licensee has also submitted the modification to NRR and is awaiting approval before placing the system in operation.
The inspectors will continue to follow work activities until the work package is completed.
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7.
Cold Weather Preparation (71714)
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The inspectors conducted a review of the licensee's cold weather preparations to ascertain that adequate measures were implemented for extreme cold weather.
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The inspectors verified that the licensee had inspected and prepared systems susceptible to freezing by verifying the operability of heat tracing, space heaters and installed insulation.
In addition, the
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inspectors reviewed the completed EMP 0120.002, Freeze Protection and Heat
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Tracing Inspection, and verified that all work had been completed and documented on task sheet PMTS: P0127777 dated November 10, 1989.
The inspectors also verified that systems which had been subjected to maintenance or modification during the past year had the heat tracing and
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~ insulation returned to operable conditions.
External liquid systems that
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provide cooling during hot weather only, have been drained to preclude freezing.
External doors were verified closed.
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No violations or deviations were identified.
8.
Licensee Quality Assurance Program Implementation (35502)
An internal office evaluation was conduc.ted of the licensee's quality assurance program by reviewing recent inspection reports, SALP reports, open items, licensee corrective actions for NRC inspection findings, and licensee event reports.
Particular emphasis was place 8 on all new items and findings,since the _ last SALP period ended (December.31,1989).
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recommendqtion to maintain NRC inspection effort at its present level was f
made.
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Other Areas The licensee made a plant modification to the V. C. Summer Station under 10 CFR 50.59 which installed a non-safety grade battery charger to provide occasional equalizing charges for battery cells of the 125 VDC station battery banks that have or may experience problems with individual cell voltage.
The resident inspectors conducted an inspection of this modification and discussed this installation with NRR.
As a result, NRR
performed an analysis of this design and issued a Safety Evaluation which is attached.
This evaluation recommends that the licensee reviso their administrative procedures to include the three recommended limits for the use of the single cell charger specified on pages 5 and 6 of the attached
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SER.
A NRR team inspection to follow-up on the licensee's implementation of NRC Bulletin's 79-02 and 79-14 started on November 27, 1989.
This inspection will be documented in inspection report 395/89-200.
The NRC Regulatory Impact Team visited the V.
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Sumw " Plant on November 29, 1989.
On November 30, 1989, the inspector observed the licensee's semi-annual emergency practice drill.
The practice drill involved only licensee personne.
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9.
Exit Interview (30703)
The inspection scope and findings were summarized on December 1,1989, with those persons indicated in paragraph 1.
The inspectors described the areas inspected and discussed the inspection findings.
The two NCV's identified in the area of maintenance and onsite follow-up of events were discussed in detail.
The licensee was made aware of the information needed to close out IFI 89-22-01 associated with the procedural changes being made to the electrical work procedure.
The inspectors noted the licensee's promptness in correcting minor deficiencies identified during inspections conducted in surveillance testing and preparations for cold weather.
No dissenting comments were received from the licensee.
The licensee did not identify as proprietary any of the materials provided to or reviewed by the inspectors during the inspection.
10.
Acronyms and Initialisms ACOT Analog Channel Operational Test CC Component Cooling DG Diesel Generator EMP Electrical Maintenance Procedure ESF Engineered Safety Feature IFI Inspector Follow-up Item LER Licensee Event Reports LIV Licensee Identified Violation MCC Motor Control Center MOVATS Motor Operated Valve Analysis Testing System MRF Modification Request Form MWR Maintenance Work Request NCN Non Conformance Notice NCV Non Cited Violation NRC Nuclear Regulatory Commission NRR Nuclear Reactor Regulation PMTS Preventive Maintenance Task Sheet QC Quality Control RCS Reactor Coolant System RCSLK9 Reactor Coolant System Leak Rate RWP Radiation Work Permits SPR Special Reports STP Surveillance Test Procedures SWIV Service Water Isolation Valve TS Technical Specifications
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ATTACHMENT
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SAFETY EVALVATION REPORT
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VIRGIL C. SUMMER NUCLEAR STATION SINGLE CELL BATTERY CHARGING
BACKGROUND
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The licensee for the Virgil C. Summer Nuclear Station has made a plant modifica-tion to permit the use of a non-safety grade 40 volt d.c. (VDC) battery charger
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to be used for occasional equalization charging of a limited number of battery cells of the 125 VDC Class IE station battery banks. At times, the charger "s
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essentially operated in parallel with a limited number of cells (minimum of 4, maximum of 17) of the battery bank, and thereby is also partially in parallel with the full capacity battery charger.
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The 40 VDC battery charger, referred to as a single cell charger, is electrically isolated from the Class 1E system by isolation fuses. Thus, the 125 VDC station
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battery is considered to be " Operable" while the single cell charger is connected to it.
The station battery manufacturer C&D Batteries, Inc., states that for some appli-
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cations sufficient equalizing potentials may not be available for equalizati,on charging and that in such cases a single cell charger with complete a.c. line isolation may be paralleled across a single cell while still a part of the over-all battery-to provide an overvoltage to that cell. C&D further notes that an equalization charge continuing for several weeks need not be cause for alarm since the currents passing through the cells are very small.
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The licensee states that they are limited by procedures to a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> equaliza-tion charge using the station's full capacity charger.
Further, they are limited to 140 VDC maximum on the station buses (2.33 VDC per cell on the 60 cell battery).
Thus, they use the single cell charger to obtain longer equalization periods and higher equalization voltages.
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The Virgil C. Sumer Station Technical Specifications require weekly surveillance
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of each pilot cell and quarterly surveillance of each cell of the 125 VDC station
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batteries.
If an individual cell, or average of all cell voltages or specific
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gravities go below a specified minimum, the battery may be considered operable if the parameters are restored within limits within 7 days. The Technical Specifications do not place any limits on how often, how long or under what con-ditions an equalization charge may be applied. However. Regulatory Guide 1.129
. references IEEE Std. 450-1975 as an acceptable standard with minor changes.
'IEEE Std. 450 indicates that an equalizing charge should be applied if the spe-cific gravity of an individual cell drops more than 0.010 or if the voltage deviates more than 0.04 Y from the average of all cells at the time of inspec-tion. Neither the Regulatory Guide nor the IEEE Standard discusses the length of time that the equalization charge should be applied or the method of imple-
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menting the equalization charge.
.The application of the single cell charger is not discussed in the Virgil C.
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Sumer, FSAR and presumably was not considered during the licensing reviews of the plant.
It is reasonable to conclude that the reviewers assumed that the full capacity battery chargers would be used for equalization charging. Thus,.
it is appropriate to consider at this time whether the use of the single cell charger will degrade the Class IE batteries or the 125 VDC system. A 10 CFR 50.59 assessment (attachment A) for the licensee by their consultant Gilbert /
Commonwealth, Inc, concluded that it would not.
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EVAL.UATION A simplified electrical diagram of the modification is shown on attachment B.
The single cell battery charger and the 3 disconnect switches, one for each of three batteries, are located in a separate room. The three fuse panels are wall mounted in their respective battery rooms. The single cell battery charger stand, teminal box, disconnect switches, fuse panels, fuses, and cable racks are
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-3-i seismically mounted. The three disconnect switches are padlocked and controlled administrative 1y to prevent more than one being closed at a time. Only two of the three batteries are safety related.
The fuses and fuse mounting components were supplied by Bussman Division, McGraw Edison.
They are qualified in accordance with Report No. 470-7 " Product Qualifi-cation Specification For Class IE Equipment. However, they'do not meet all of the requirements for Class 1E equipment because Bussman no longer complies with
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the paperwork involved in Report 470-7II)
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.The fuses are 150 amperes fast acting (0.75 seconds at 300 amperes) to clear battery fed faults between the fuses and charger.
Flexible cables with clip terminal connectors are coiled on wall mounted racks near the fuse panels for connecting to the battery terminals when needed for equalization charging. These cables and clips are not class 1E but would be adminjstratively controlled by inspection and placement to insure that they are-in good. condition and do not contact the battery rack or battery terminals.
One of our initial concerns with the single cell charger application was with a possible fault between the fuses and the charger which could result in a fault current slightly less than the 150 ampere rating of the fuses. The licensee pro-
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vided additional information (2) as to why such an event was improbable.
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reasons given included the following:
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(1) Letter from Jim Calzone, Bussman Division, to Senath Dasgupta, Gilbert Associates, Inc., October 21, 1986.
(2) Letter, O. S. Bradham, South Carolina Electric and Gas Company to U.S. Nuclear Regulatory Commission, August 15, 1988.
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o Cables are run in conduit only.
o The majority of the cable length is run in separate conduits for each pole.
o Cables are separated by a minimum 5" spacing where possible in the disconnect switches and fuse panels.
o Cables are purchased nuclear safety related.
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o There is fault detection by ground indicating lights.
o Positive and negative cables must fail simultaneously.
Another concern was with a possible voltage regulator failure and a resultant
.overvoltage on the limited number of battery cells receiving an equalizing charge.
ThelicenseerespondedthatC&DBatteries,Inc.calculatedthatacellpassing 150 amps would take approximately eight hours to reach the cells low water level
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due to the heat generated and the breakdown of the water through electrolysis.
Therefore, the licensee has committed to a battery check every six hours during such an equalizing charge to assure that the battery will not be damaged by such I
an event.
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L A third concern was with a loss of input power to the single cell charger and a
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I resulting drain on the battery. The licensee responded that the maximum drain would be 7.9 amps or 47.4 ampere hours (AH) over the 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> that could occur between checks of the single cell battery charger. The 47.4 AH is 4.5% of a connected cells 1050 AH capacity.
A fourth concern was with the possibility of the cables between the fuse panels and batteries, or the cable clips to the battery, causing a battery short. The
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licensee's administrative procedures require inspection of the battery cables to insure their integrity and careful placement of the cables and battery clips to insure that the cables do not cross the battery terminals and that the clips will fall to the ground if they become dislodged.
i Based on the licensee's responses and our review of the modification details, we conclude that utilization of the non-class IE battery charger will not signifi-cantly increase the exposure of the Class 1E system to additional hazards. Also, we recognize the advantage in some instances of an equalization charge to a limited number of cells in improving overall battery reliability.
However, we are concerned that over utilization of the single cell charger may mask a problem with an individual cell or cells in the battery.
In response to a staff question as to the average number of hours that the single cell charger would be connected l
to a safety-related battery during a year, the licensee estimated 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />, but noted that there was no limit on the number of hours that it could be connected.
We believe that some limit should be imposed. The licensee states that the single
cell charger must be disconnected for surveillance testing of the battery under i
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the Technical Specifications. However, the Technical Specifications allow up to 92 days between surveillance tests of each connected cell. One or more degraded cells could be temporarily corrected using the single cell charger and the true degraded condition of the cell undetected until the next 92 day surveillance, at which time the single cell charger could be applied again. Although such a problem-could be detected by a cell-trending program, the licensee states that there is no formal trending program that reviews individual cell data.
Thus, we conclude
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that a limit should be placed on the number of occasions and amount of time that the single cell charger can be used on a safety-related battery as follows.
First, on the safety-related battery banks the single cell charger should not be used in place of the nonnal Class 1E full capacity charger if adequate equali-zation of cell voltages can be maintained using the full capacity charger.
Second, the single cell charger should not be used more than once a year on any
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individual cell. Adequate records should be kept to assure this condition is
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satisfied. After equalization charging of a limited number of cells using the j
single cell charger, in addition to the normal surveillance of those cells for j
operability following the equalization charge, they should be checked again in two weeks, plus or minus 2 days, to assure that they have held the charge by maintaining a voltage of it2.13 volts corrected for average electrolyte tempera-ture.
If not, the battery should be declared inoperable. Third, for a constant voltage equalization charge, the charging time after the charging current has stabilized should not significantly exceed the values indicated below for a
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lead-calcium battery.
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TIME-IN HOURS Charger Volts 1.215 sp. gr.
1.250 sp.gr.
Per Cell *
Battery Battery
2.24 222
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2.27 166
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2.30 105
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2.33
.-WT /4 2.36
118 2.39
80
- Charger voltage divided by number of cells being charged.
We find the use of the single cell charger to be acceptable provided provisions equivalent to those above are included in the administrative provisions for use of the single cell charger.
SUMMARY AND CONCLUSION The licensee for the Virgil C. Summer plant has made a plant modification to l
electrically isolate and utilize a non-class 1E battery charger for placing an I
equalizing charge on a limited number of cells of the 125 volt d.c. Class IE station batteries. The battery manufacturer has found the practice to be acceptable, and a 10 CFR 50.59 assessment concludes that the application imposes no unreviewed safety questions. The NRC staff has reviewed the plant I
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modification and finds that utilization of the non-class IE battery charger will not significantly expose the Class IE system to any additional hazard, and the
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small increase in exposure is offset by an expected improvement in battery reli-ability, provided the non-class IE battery charger is not used excessively to
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mask possible individual cell degradation. We therefore find the application
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of the non-class IE battery charger to be acceptable provided certain additional provisions are included in the administrative procedures for use of the non-class IE battery charger. The provisions should be equivalent to those listed above in the body of this evaluation. The licensee should include such provi-sions in their administrative procedures and submit them for staff review.
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$ ALP INPUT
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FACILITY NAME:
Virgil C. Summer
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SUMMARY OF REVIEW:
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Safety review of licensee's proposed use of a non-class 1E battery charger for equalization charging of a limited number of cells in the station 125 volt safety-
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related battery banks. The review was conducted by NRR/ DEST /SELB during the latter half of 1988. The staff found the use of the non-class IE charger acceptable provided the licensee includes additional provisions in their administrative procedures for its use.
NARRATIVE DISCUSSION OF LICENSEE'S PERFORMANCE
- FUNCTIONAL AREA - ENGINEERING / TECHNICAL SUPPORT:
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The safety review was relatively complicated in that it required a review of the design provisions of the non-class 1E battery charger installation to assure that it was adequately electrically isolated from the Class 1E battery bank and also to determine the acceptability of equalization charging of a limited number of cells rather than the total number of connected cells. This is not done else-
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where at nuclear power plants and could be precedent setting.
Therefore, the
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staff conducted a thorough investigation which required several contacts with the licensee.
During telecon contacts, we found that the technical personnel contacted in some instances could not respond immediately to some staff questions indicating that they were not completely familiar with the technical aspects. However, in evalua-
ting this aspect of the licensee's performance, we need to consider that this was a 50.59 review conducted by an outside consulting firm. Given time, the licensee responded completely and satisfactorily to our questions, thus indicating proper responsiveness and adequate management involvement and control.
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ATTACHMENT A i
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\\,GIL C. SUMMER NUCLEAR ST
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G/C MODIFICATION SAFETY EVALUATION he*isc
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10 CFR 50.59 ASSESSMENT
"'VISI'" 1 i
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A.
E valveipon appi. cab 6e to: u=* toert.seanie een senery chaeoer B.
Answerovestions 1 thru 4.
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Does this design thenee/ modification constitute:
1.
Yes L No - A change to the plant as described in the FSAMPE Rt 2.
Yes No 1 A change to procedures as described in the F1AMPt Rt 3.
Yes _ No.1 A test or esperiment not described in the F5AM PIR?
4.
Yes _ No L A change to the plant Technical $pecification?
C.
Answer unreviewed safety ouestions 1 thru ?.
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1.
Yes No.1 Will the proba bility of an occurrence previously evaluated in the F$ AMPE R be increased ?
2.
Yes _ No.L Willthe conseguence of an accident previously evaluated in the F$AMPER be increased'
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Yes No L Willthe probability of a realfu ction of equipment important to safety previously evstwatedin the F$AR TPE R n
be incre ased'
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Yes No L.,
Will the conseovences of a malfunction of equipment important to safety previously evaluated in the
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F5AM PE R be increated ?
s. Yes _ No.1 May the possibihty of an accident which es diffe rent from any already evaluated in the F$AMOR be created ?
6.
Yes No.1 May the possibility of a malfunction of equipment important to safety different from any already evaluated an tne F$AM PE R be c'ested ?
7.
Yes No.X Will the margin of safety as defined in the bases to any Technical $pecihcation be reduced?
D.
Provide justification for answers in Part C of the $afety ivaluation?'
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This modification permanently installs a single cell battery charger used for temporarily providing an equalizing charge in excess of 2.33 Volts per cell (VPC) to assure required i
battery capacity and for battery life extension.
All equipment will be seismically mounted in accordance with anti fall down criteria.
Isolation fuses between the batteries and charger are provided to prevent a fault downstream of the fuses from draining the connected cells. The fuses are located in each battery room to minimize the amount of cable between the battery and fuses. The fuses are of a semiconductor type application that clear on small overcurrents in a small amount of time (.75 seconds at 200% of 150A rating).
X 5ee attached sheets:
(Yes)
(No)
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Discipline Review and Concurrence
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interf ace Signature Recuired TECH 5PEC.CH ANGt/ REFERENCE'
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change neference lection Page Of5CittiNE af seoN$iptt (NGINT t R DATE X
4.8.2.1 3/489 l
flectrical-
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Controt s yste mi-F5 AM P[R CH ANGE/ RIFE RE NCE'
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change Reference Section Page
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X Appendix 3A 3A 42a,43 X
Table 3.11 0A 3.11 100
- Use additionalsheetsif necessary.
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VliaillC.5UMMER NUCLEAR STA.ON f*-
G/C MODIFICATION SAFETY EVALU ATION Pese 2 of 3 Revision 1 10 CFR 50.59 ASSESSMENT tv iuanon.ppiec dieto: MRF 20827 - Single Cell Battery Charger
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P, ovide justification for answers m Part C of the saf ety ivaluationMcontmued)
D.
Upon loss of a.c. input power to the charger, the charger will not act as a "short" across the battery cells being equalize charged. The reason for this is the output SCR's are turned
"off" due to loss of their gate control voltage. The charger's output shunt resistors plus the external circuit resistance is a high resistance path relative to the battery cells resistance
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causing insignificant load current to flow to the charger, if the battery charger current limiter controls fail, the output current will exceed 175 A. The isolation fuses (150A) will clear the f aulted charger before cell damage occurs. No~ credit has been taken for the internal charger circuit breaker to clear this condition,which in f act it will attempt to do.
- If the battery charger voltage regulator controls partially fail,the voltage impressed on each cell being charged may exceed the manufacturer's recommended maximum Walizing voltage. This condition will be handled by an administrative procedure that requires checking the voltage everytthours. If this voltage value is exceeded,the charger is disconnected and a visualinspection of the cell and water level are required. No damage to the cells should occur as each_ cell can withstand 2.9V carrying 52.5A for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
If the charger voltage regulator controls completely fall and call for maximum output voltage, the charger would go to current limit in an attempt to raise the cell's voltage beyond 2.9V. 2.9V is the maximum that can be impressed on a cell due to its physical characteristics. The charger's output current will exceed 175 A and the isolation fuses
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(150A) will clear the f aulted charger. The charger's current limit controls will be set at
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maximum to allow a current value that can clear the fuses in the event the voltage controller f ails but the current limiter controls remain operable.
The disconnect switches (one per battery) will be padlocked and controlled administratively to prevent more than one being closed at a time and thus tying two batteries together.
Signs will be installed on the isolation fuse panels stating the maximum and minimum number of battery cells to be charged simultaneously due to charger output or acceptable fault current level, and to maintain a minimum of 6" space between the ( +) and (-) cables.
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One set of isolation fuses per battery are provided. The 125V d.c. sy) stem is a floating s (no system ground). A f aultis generated when both the ( +) and ( cable conductors come in contact. The fault current must sass through both the ( +) and (-) fuses, if either fuse clears, the f ault path is interrupted. The ( + ) fuse is therefore back up protection for the (-)
fuse and vice versa.
The use of NNS battery cable and NNS battery clips is acceptable for the single cell battery charger application based on the requirements of an administrative procedure to be developed. This procedure will require a visualinspection of the cable prior to its connection to the battery, and direct the placement of the cables such that they do not cross over any cell or cell connectors. The procedure will also direct the placement of the clips such that one cable will not touch the battery rack and during a seismic event the weight of the cable attached to a clip that has become loose,will cause the clip to f all to the floor and not across cell posts or connectors, ms. ae, 3
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V...GIL C.5UMMER NUCLEAR ST. ilON
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G/C MODIFICATION SAFETY EVALU ATION Pes * 3 of 3 Revision 1
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10 CFR 50.59 ASSESSMENT a
t..iue0n.ppi.c.bie t0: MRF 20827 - Single Cell Battery Charger D.
Providt justilitatichIOf answers in P rt C Of the safety tvaluateOnNcontinued)
A single cable i.l. lure such that it contacts the battery rack while connected to a cell will not short out the battery as the 125V d.c. system is an ungrounded system. A fault is generated when both the ( + ) and (-) cables come in contact or are connected together by a common ground path. The administrative procedure described in the previous paragraph will direct cable and clip placement such that a battery fault will not be possible for the charger leads failure.
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ATTACHMENT B i
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3-Phasey.c.
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Battery t
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Charger
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2 conductor d.c.
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In conduit T
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2 conductors d.c.
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In conduit
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Isolati>n Fuses
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Coiled Cable on wall Q
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