ML20050B274
| ML20050B274 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 03/23/1982 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsil W CONNECTICUT YANKEE ATOMIC POWER CO. |
| Shared Package | |
| ML20050B275 | List: |
| References | |
| LSO5-82-03-094, LSO5-82-3-94, NUDOCS 8204050160 | |
| Download: ML20050B274 (7) | |
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March 23, 1982 Docket NRC PDR Local PDR Docket No. 50-213 ORB Reading i
NSIC LSO 5-82-03-094 DCrutchfield HSmith CTropf Mr. W. G. Counsil, Vice President OELD Nuclear Engineering and Operations 0IE Connecticut Yankee Atomic Power Company ACRS (10)
?ost Office Box 270 SEPB Hartford, Connecticut 06101 DPrevatte
Dear Mr. Counsil:
SUBJECT:
ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES RE:
Haddam Neck Plant We have completed our review of the captioned matter for the Haddam Neck Plant and find that the offsite power system and the onsite distribution system are capable of providing acceptable voltages for worst case station electric load and grid voltages. Our support-ing Safety Evaluation and the attached Technical Evaluation Report dated February 1, 1982, prepared by our consultant, Lawrence Livermore Laboratory are enclosed.
The two single events you identified that could result in the loss of both offsite power sources will be analyzed as part of SEP Topic VII.3, " Systems Required for Safe Shutdown".
Sincerely, l
E Dennis P. Crutchfie d, hief Operating Reactors Branch #5 Division of Licensing
Enclosure:
Safety Evaluation, with gN 2/1/82 TER attached (b
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Mr. W. G. Counsil CC Day, Berry & Howard Counselors at Law One Constitution Plaza Hartford, Connecticut 06103 Superintendent Haddam Neck Plant RFD #1' Post Office Box 127E East Hampton, Connecticut 06424 Mr. Richard R. Laudenat Manager, Generation Facilities Licensing Northeast Utilities Service Company P. O. Box 270 Hartford, Connecticut 06101 Board of Selectmen Town Hall Haddam, Connecticut 06103 State of Connecticut 0Ffice of Policy and Management ATTN: Under Secretary Energy Disision 80 Washington Street Hartford, Connecticut 06116 U. S. Environmental Protection Agency Region I Office ATTN: Regional Radiation Representative JFK Federal Building Boston, Massachusetts 07203 Resident Inspector Haddam Neck Nuclear Power Station l
c/o V. S. NRC East Haddam Post Office East Haddam, Connecticut 06423 l
Ronald C. Haynes, Regional Administrator Nuclear Regulatory Commission, Region I 631 Park Avenue l
King of Prussia, Pennsylvania 19406 l
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SAFETY EVALUATION HADDAM NECK NUCLEAR POWER PLANT DOCKET NO. 50-213 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES I
INTRODUCTION AND
SUMMARY
I l
Connecticut Yankee Atomic Power Company (CYAPCO) was requested by'NRC letter dated August 8,1979 to review the electric powe#r system at Haddam Neck
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Nuclear Power Plant. The review was to consist of:
1 a) Determining analytically the capacity and capability of the offsite power system and onsite distribution system to automatically start as well as operate all required loads within their required voltage ratings in the event of 1) an anticipated transient, or
- 2) an accident (such as LOCA) without manual _ shedding 'of any electric loads.
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b) Determining if there are any events or conditions which could result in the simultaneous or, consequential loss of both required circuits from the offsite network to the onsite electric distribution system and thus violating the requirements of GDC 17.
The August 8,1979 letter included staff guidelines for performing the required voltage analysis and the licensee was further required to perform a test in order to verify the validity of the analytical results.
CYAPC0 responded by letters dated November 15,1979, March 6,1980, 1
August 21. 1980, November 4, 1980, October 23,'1981, and December 10, 1981.
a 2-A detailed review and technical evaluation of the submittals was performed by LLL under contract to the NRC, with general supervision by NRC staff.
This work is reported by LLL in Technical Evaluation Report (TER),
" Adequacy of Station Electric Distribution System Voltages, Haddam Neck Nuclear Power Plant," dated February 1,1982 (attached). We have re; viewed this report and concur in the conclusions that the offsite power system and the onsite distribution system are capable of providing ac'ceptable voltages for worst case station electric load and grid voltages.
I EVALUATION CRITERIA The criteria used by LLL in this technical evaluation of the analysis includes GDC 5 (" Sharing of. Structures, Systems, and Components"),
GDC 13 (" Instrumentation and Control"), GDC 17 (" Electric Power Systems")
of Appendix A to 10 CFR 50; IEEE Standard 308-1974 (" Class IE Power Systems for Nuclear Power Generating Stations").. ANSI C84.1-1977
(" Voltage Ratings for Electric Power Systems and Equipment - 60 Hz"),
and the staff positions and guidelines in NRC letter to CYAPC0 dated August 8, 1979.
ANALYSIS AND TEST FEATURES CYAPC0 analyzed each offsite power source to the onsite distribution system under maximum and minimum load conditions with the 115 kv offsite power sources at maximum and minimum voltages. The maximum offsite power system voltages used in the analysis was 117 kv; however, present operating limits specify an upper voltage limit of 114.7 kv. The minimum offsite grid voltage used in the analysis was 106 kv. The 106 kv value is below the administrative limit of 110.8 kv for one station service transformer 1
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e 3-9 operation and 106.4 kv for two station service transformer operation.
Typical calculated voltage drops of 10 volts for 480 V running loads, 50' volts for 480 V starting loads, 20 volts ;for 4160 V running loads, and 100 V for 4160 V running loads were used in the analyses. Both charging pumps, all service water pumps and all containment atmosphere recirculation fans O
When were considered in operation for normal full load, case studies.
starting an individual load, the running load of that motor was still considered as part of the existing load, thus creating a more conservative Additionally the transient effects created by starting a large cnalysis.
non-Class 1E load with the Class 1E bus fully loaded was included as a part of the analysis.
The worst case Class 1E equipment voltages occur under the following conditions:
2 Maximum voltage occurs when the offsite grid is at the highest 1.
analyzed voltage, the unit is in shutdown mode and either station service transformer 1 or 2 is in service.
Minimum voltage occurs when the offsite grid is at the lowest 2.
analyzed voltage, two station service transformers are in service, plant trip with LOCA, normal full loads on the buses and all accident loads starting and running.
l The voltage analysis supplied by the licensee indicates that with two service transformers available the grid must be niaintained above 106 kv and with one service transformer available the grid voltage must be i
maintained above 110.6 kv to provide acceptable Class 1E equipment voltages.
Additionally the analysis results indicates that for the max'imum grid voltage minimum load condition the voltage to 480 volt Class lE equipment may exceed the equipment design rating by 2%. The licensee has proposed to install overvoltage monitors on the 4160 volt. and 480 volt buses with i,
annunciation in the control room..This slight overvoltage condition is not. considered significant since the alarm will allow operator action to reduce this overvoltage and any significant loading of equipment on the buses could additionally reduce the voltage to within safe operating limits.
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The voltage analyses was verified by taking measurements on the grid and each of the buses with plant operating and the Class lE buses loaded from 29 to 91 percent. The measured voltages when compared to the calculated voltages produced errors of -0.86% and -2.56% for the 4160 V and 480 V l'*
buses respectively.' A minus percentage error indicates the measured values are higher than the calculated values. This correlation showed the analyses to be conservative.
CYAPC0 has identified two events which could result in the simultaneous l
loss of both offsite power sources. These two events will be analyzed l
as part of the Systematic Evaluation Program (SEP) topic VII.3, " Systems Required for Safe Shutdown."
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m DESIGN CHANGES As a result of the voltage analyses CYAPC0 has proposed to install overvoltage monitors on the 4160 V and 480 V Class 1E buses with annunciation in the control room.
l CONCLUSIONS We have reviewed the LLL technical evaluation report and concur in its findings that:
1.
By installing overvoltage monitors with annunciation in the control room, operator action can be taken to eliminate any overvoltage on Class 1E equipment.
2.
CYAPC0 has provided a verified voltage analyses which demonstrates that Class lE equipment voltages will remain within acceptable limits for the worst case loading. This is based on the provision'that '
minimum grid voltage of 106 kv is maintained when two station service transformers are in operation and 110.6 kv is maintained if only one i
station service transformer is available.
3.
The licensee has identified two events which could result in the simultaneous loss of both offsite power sources. The two events will be analyzed as a part of the Systematic Evaluation Program (SEP) topic VII.3.
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