ML19291C497
| ML19291C497 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 12/27/1979 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Mattson R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8001240502 | |
| Download: ML19291C497 (2) | |
Text
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UNITED STATES y ( '3.- ( f,g NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D. C. 20555 o'
December 27, 1979 5
Roger J. Mattson, Director Division of Systems Safety Operating Experience Memorandum No. 23 POTENTIAL OVERVOLTAGE CONDITION - OYSTER CREEK Problem An analysis conducted by Jersey Central Power and Light Company, pursuant to our letter of August 8,1979, (Re: Adequacy of Station Electric Distribution System Voltages) showed that under certain conditions an overvoltage situation could exist on the 460 volt safety bus.
Analysis In order for this event to occur, the Oyster Creek Station would be in the shutdown condition with a load of 2.5 MW or less on the startup transformer. A maximum grid voltage of 238 KV under these conditions would result in a voltage of 498 volts on the 460 volt bus. Safety related motors on this bus are rated at 440 volts +_
10%; therefore, the voltage at the motor would be in excess of the 484 volt maximum. Although the motor would have excessive voltage on starting, the voltage would decrease to acceptable levels on startup of the safety loads due to resistive losses in the transformer.
Corrective Action Standing Order No. 24 was issued on May 22, 1979, which requires the operator to maintain the 34.5 KV bus A and B potential voltages such that the instrument buses remain between ll4V and ll8V. This provides administrative control to assure that an overvoltage situation will be precluded.
Furthermore, during the upcoming refueling outage, automatic voltage regulators will be installed on the startup transformers to automatically control the voltage within acceptable limits.
1793 155 01 8001240
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Roger J. Mattson December 27, 1979 Safety Significance Safety related motors can normally operate continuously at a voltage of 110% from the rated value. However, sustained overvoltage conditions at the safety bus could lead to degradation of the associated electrical components.
D0R Action By letter dated August 8,1979, D0R has requested all operating facilities to review their electric power systems and determine whether the offsite power system and the onsite distribution system is of sufficient capacity and capability to automatically start as well as operate all required safety loads if all onsite sources 7/ AC power are not available.
Licensees were requested to provide assurance that actions taken to assure adequate voltage levels for safety loads would not result in overvoltage conditions.
D0R is looking at overvoltage problems as part of our ongoing evaluation of the adequacy of station electric systems.
Recommendations D0R recontends that an assessment be made of the applicability of the corrective actions taken at Oyster Creek to those plants currently under licensing review. We also recommend more comprehensive enforcement, with regard to the overvoltage concern, included in the positions stated in Enclosure 1 (Staff Positions Relative to the Emergency Power Systems for Operating Reactors) to the June 5,1977 letter sent to all licensees.
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% @re g./ I 2aw u Da Eiisenhut,Acti g Director Division of 10perating Reactors
Contact:
R. Kendall, X28218 cc:
H. Denton J. Sniezek E. Case L. Nichols D. Vassallo G. Lainas D. Muller R. Satterfield D. Eisenhut F. Rosa R. Tedesco V. Thomas E. Jordan E. Wenzinger DSS ads J.E. Knight DOR ads D. Tonid D0R BCs R. Kendall D0R SLs PSB Section A 1793 156 1