ML19344D259
| ML19344D259 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 02/29/1980 |
| From: | Widner W GEORGIA POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| IEB-79-27, NUDOCS 8003110604 | |
| Download: ML19344D259 (4) | |
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Power Ganeration Department Georg a Power February 29, 1980 U. S. Nuclear Regulatory Commission.,
Office of Inspection and Enforcement
REFERENCE:
Region II - Suite 3100 RII: JPO 101 Marietta Street, NW 50-321/50-366 Atlanta, Georgia 30103 I&E Bulletin 79-27 Attention:
Mr. James P. O'Reilly Gentlemen:
The following information is submitted in response to your letter dated November 30, 1979, which transmitted I&E Bulletin 79-27, " Loss of Non-Class 1E Instrument and Control Power System Bus During Operation".
The design reviews requested in the bulletin are being performed for Plant Hatch Units 1 and 2 by Bechtel Power Corporation at the direction of Georgia Power Company. A summary of the results achieved thus far are provided below:
1.
Item 1 of the bulletin requires a review and identif! cation of all instrument and control system loads connected to b w n, and an identification of the alarm and/or indication which is provided in the control room.
This review has been completed for all the Class IE buses for Unit 1 and Unit 2 and for the Non-Class 1E bus R25-5063 for Unit 1 and 2R25S063 for Unit 2.
These Non-Class lE buses are the vital A.C. distribution panels supplied from the inverters described in item 3 of the bulletin.
The results of the review are provided on a panel-by-panel basis in a report, prepared by Bechtel Power Corporation, which is available at the plant site for NRC review. As shown in the report, alarm and/or indication is provided to the main control room to indicate loss of power to the buses for all buses except R25-S035 and 2R25-S035. The loss of these panels would not affect the ability to achieve a cold shutdown condition. The only essential circuits on these panels are the switchgear rooms IF ventilating fan and fan damper and the switchgear room 2F ventilating damper, respectively, which would close on loss of power. Should these buses fail, plant personnel making rounds would have an indication of failure in that the emergency lighting in the switchgear room would be operating.
Power for the nornal lighting is provided from these buses.
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4 GeorgiaPower d U. S. Nuclear Regulatory Commission February 29, 1980 Page Two Each circuit was analyzed to determine its effects on the ability to achieve a cold shut down condition. This portion of the investigation resulted in finding two circuits, one on each unit, which had been inadvertently placed on the Non-Class IE power supply, vital A.C. distribution panel. This was reported in Licensee Event Report No. 18016.
Details of the finding and the modification schedule are included in the LER.
The review of the remaining non-class IE buses is expected to be completed by March 28, 1980. During the continuing review, any additional circuits found which could affect the ability to achieve a cold shutdown will also be reported as Licensee Event Reports.
2.
Item two of the bulletin requires that a review be conducted of emergency procedures used by control room operators upon loss of power to each class 1E and non-class 1E bus supplying power to safety and non-safety related instruments and control systems.
Georgia Power Company, in response to NED0-24708, has requested Bechtel Power Corporation to review the existing emergency procedures for mitigating the consequence of the event considered in the NEDO document. NEDO-24708 is the generic document produced by General Electric Company at the request of the BWR Owners Group in response to the questions posed by the TMI Bulletin and Orders Task Force.
In addition, Georgia Power Company has now included in ebe review requirements the items specifically required in Item 2 of I&E Bulletin 79-27. This review for I&E Bulletin /9-27 will begin immediately rfter the evaluation of circuits and alarms being censidered in item 1 of this bulletin is complete. This continuing review of existing emergency procedures to meet the requirements of the NEDO and this bulletin will provide a comprehensive study of existing emergency procedures.
The estimated schedule for completion of this integrated study of procedures is January 31, 1981.
3.-
Item three of the bulletin requires a review of both class 1E and non-class 1E safety-related power supply inverters to include the items discussed in IE Circular No. 79-02, " Failure of 120 Volt Vital AC Power Supplies". The following is a discussion of the results of the review for each item of the circular.
Item i None of the inverters used at Plant Hatch Unit 1 or 2 contains an automatic transfer function with a' static switch, therefore no time delay function is incorporated
.in this design.
GeorgiaPower A U. S. Nuclear Regulatory Commission February 29, 1980 Page Three Item 2 The A.C. input to the Vital A.C. System Inverters, R44-S001 and 2R44-S001 are applied first to the battery charger. This input is applied to the primary of a three phase Delta to. Wye connected power transformer.
This transformer steps down the A. C. input voltage of 600 Volts to 120 volts. A charge control board is used to generate output pulses which are used to gate on the power handling SCR's in the proper sequence and at the proper time. The output pulses will be phase-delayed in a given 1/2 cycle so as to maintain constant output voltage, 125V D.C., when the A.C. input voltage rises.
This constant 125V D.C. is then used as the input to the inverters for conversion to 120/240 Volt A.C.
The inputs of the remaining inverters used at Plant Hatch are directly supplied from the station battery D.C. System and therefore are not subject to high A.C. input voltage transients.
Item 3 A manual only transfer to an alternate 120V source is provided for the Vital A.C. System of Plant Hatch Units 1 and 2 thus no transient loading condition can cause a transfer to occur.
Item 4 Georgia Power Company does enploy administrative controls that ensure the operability of safety systems after subcomponent have been subjected to maintenance or testing.
This control may take several forms, i.e. visual inspection, written test, plant procedures.
If you have any questions or comments in this regard, please contact my office.
Yours very truly,
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W. A. Widner Vice President and General Manager Nuclear Generation JAB /mb
i GeorgiaPoner A i.
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. U. S. Nuclear Regulatory Commission' February 29, 1980 Page Four j
xc: Director of the Office of Inspection and Enforcement Director of the Division of Operating Reactors, Office of j
Nuclear Reactor Regulation i
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