ML20050F891
| ML20050F891 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 04/05/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20050F890 | List: |
| References | |
| TAC-10026, TAC-12831, TAC-12832, TAC-47044, NUDOCS 8204130476 | |
| Download: ML20050F891 (5) | |
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ENCLOSURE SAFETY EVALUATION EDWIN I. HATCH NUCLEAR POWER PLANT UNITS 1 & 2 DOCKET NOS. 50-321/366 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES INTRODUCTION AND
SUMMARY
Georgia Power Company (GPC) was requested by NRC letter dated August 8, 1979 to review the electric power system at Edwin I. Hatch Nuclear Power Units 1 and 2.
The review was to consist of:
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.
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.
GPC responded by letters dated December 7, 1979, April 28, 1980, October 9,1980 and January 12, 1982. A detailed review and technical evaluation of the submittals was performed by EG&G under contract to the l
NRC, with general supervision by NRC staff. This work is reported by 8204130476 820405 PDR ADOCK 05000321 P
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8 2-EG&G in Technical Evaluation Report (TER), " Adequacy of Station Electric Distribution System Voltages, Edwin I. Hatch Nuclear Power Plant, Units 1 and 2," dated February,1982, We have reviewed this report and concur in the conclusions that the offsite power system and the onsite distribution system are capable of providing acceptable voltages for worst case station electric lead and grid voltages.
EVALUATION CRITERIA The criteria used by EG&G 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 lE Power Systems for Nuclear Generating Stations"), ANSI C84.1-1977 (" Voltage Ratings for Electric Power Systems and Equipment - 60 Hz"), and the staff positions and guide-lines in NRC letter to GPC dated August 8,1979.
ANALYSIS AND TEST FEATURES GPC analyzed each offsite power source to the onsite distribution system under maximum and minimum load conditions with the 230 kv grid at maximum and minimum anticipated voltages of 239.2 kv and 225.4 kv. The worst case Class lE equipment voltages occur with startup transformer ID, Unit 1, or startup transformer 2D, Unit 2, supplying power to the Class.1E buses under the following coaditions:
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. 1.
The maximum expected bus and load voltages occurs when the grid is at the maximum anticipated voltage (239.2 kv) with one unit operating and the second unit shutdown.
2.
The minimum expected continuous bus and load voltages occur when the grid is at the minimum anticipated voltage (225.4 kv) with one unit in shutdown and a LOCA on the second unit.
3.
The minimum expected transient voltages occur immediately prior to 2 above due to automatic and simultaneous start of the Class 1E loads and a condensate pump.
The analysis results indicates that during the worst case transient analyzed under the condition of 3 above the voltage levels at 208 volt level may drop to 71.2% of nominal bus voltage. Under these conditions any 208 volt motor or. motor starter contactor required to operate may be delayed for approximately four seconds until the voltage recovers above 75%, at which time the contactors will pickup and the motors will have sufficient voltage to start and accelerate. During this time no contactor dropout or load shedding will occur. During this analyzed transient, the voltage will be maintained above the 70% motor stall rating and no damage to the Class lE equipment will occur. The voltage will recover to the equipment continuous duty rat'ing in less than 12 seconds. Due to the short duration of this transient and since no damage will occur to the Class lE equipment under this worst case condition analyzed, we find the. voltage analysis acceptable.
j The voltage analysis was verified by taking voltage and load measurements on the grid, generator, 4160 volt Class 1E buses and at selected equipment with unit 1 operating and Unit 2 shutdown. GPC did not take measurement at voltage levels below 4160 volts because all inputs to the voltage analysis for levels below 4160 volts were based upon actual inplant measurements and did not require further verification. The comparison showed that the calculated voltages are within 0.58% of the measured voltages. This close correlation verifies the accuracy of analysis submitted.
DESIGN CHANGES As a result of the voltage analysis.GPC changed the tap settings from 1.00 to 0.925 pu on all Hatch station transformers that supply voltages of less than 600 volts.
CONCLUSIONS We have reviewed the EG&G Technical Evaluation Report and concur in the findings that:
1.
GPC has provided a verified voltage analysis to demonstrate that Class lE equipment voltages remain within acceptable operating limits for the postulated worst case condition.
2.
The voltage analysis was verified by tests and the close correlation showed the analysis to be accurate.
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. 4 3.
GPC's reaffirmation of compliance to GDC 17 is acceptable.
1 1
We.therefore find the Edwin I. Hatch Units 1 and 2' design to be w.
t acceptable with respect to the adequacy of station electric distribution system voltages.
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