ML19209A058
| ML19209A058 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 08/11/1978 |
| From: | Boyd R Office of Nuclear Reactor Regulation |
| To: | Stampley N MISSISSIPPI POWER & LIGHT CO. |
| References | |
| GL-78-32, NUDOCS 7910010831 | |
| Download: ML19209A058 (4) | |
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NUCLEAR REGULA TORY COMMisslON NRC PDR
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,y August 11, 1978 D. Vassallo
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50-416 C. Thomas and 50-417 E. Hylton OELD B. Scott L. Dreher - G-26 Mississippi Power and Light Company ATTN:
Mr. N. L. Stampley Vice President - Production p
P. O. Box 1640 Jackson, Mississippi 39205 g1
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SUBJECT:
REACTCR PROTECTION SYSTEM POWER SUPPLIES (GRAND GULF NUCLEAR STATION, UNITS 1 & 2)
Criterion 2 of the Ccroiss ~on's General Design Criteria (Appendix A to 10 CFR Part 50) requires i; part that systems important to safety, such as the reactor protection system, be designed to withstand the effects of earthquakes. Reactor protection systems are required to be Class IE systems, hence they are seismic Category I.
The normal reactor protection system pcwer supplies for most General Electric Company boiling water reactor nuclear steam supply systems, except for those utilizing solid state reactor protection systems, consist of redundant alternating current motor-generator sets which are not seismically qualified.
Juring the course of our review of Georgia Power Ccmpany's operating license application for its Edwin 1. Hatch Nuclear Plant Unit No. 2 (Docket No.
50-3co), we questioned the adequacy of the protection af forded the reactor protection system against possible sustained over-voltage, under-voltage, or underfrequency conditions from the reactor protection system pcwer supplies.
Specifically, we questioned the capability of the reactor pro-tection system power supplies to acccamodate the effects of earthquakes without jeopardizing the capaaility of the reactor protection system to to perfom its intended safety function.
We deternined that a sequence of events initiated by an earthquake can be postulated which could result in damage to the reactor protection system components with the attendant potential loss of capability to scram the plant. This sequence of events includes (1) the occurrence of an earthquake that would cause the undetected failure of a voltage sensor, (2) the failure of a notor-generator set resulting in an abnamal output voltage, (3) the
- e sistence of this abnormal output voltage, undetected by visual observa-
- cos ed surveillance testing, for a time sufficient to damage reactor protecticn system ccgonents, and (4) failure of these ccmponents in such a.aanner that results in the loss cf capability to scram the plant.
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FU0n 0sdJ Bdb August 11, 1978 We, therefore, required that prior to startup following the first scheduled refueling outage, Georgia Pcwer Ccmpany install Class IE systems approved "sy us and capable of de-energizing the reactor protection system power supplies when their output voltages exceed or fall below or their output frequencies fall below limits within wi.. '.e the equipment being powered oy the power supplies has been designed and qualified to operate con-tinuously and withcut degradation. With such systems, the designs of the reactor protection system power supplies will confonn to the applicable requirements of Criterion 2 of Appendix A to 10 CFR Part 50.
Consistent with our finding on Hatch Unit 2, we require that all applicants for licenses to construct and operate plants utilizing General Electric Company coiling water reactor nuclear steam supply systems with non-seismic Category I alternating current motor-generator sets as the nonnal reactor protection system power supplies install Class IE systems approved by us and capaole of de-energizing the reactor protection system power supplies wnen :neir output voltages exceed or f all belcw or their output frequencies f all below limits within which the equipment being powered by the power supplies has been designed and qualified to operate continuously and without degradation.
We will implement this requirement as follows:
(1) For those applicants w(th applications in the construction permit stage of the review process, we request that within 30 days of your receipt of this letter, you amend your application to reflect your comnitment to (a) install such systems prior to initial fuel loading and (b) provide the details of the system design in your Final Safety Analysis Report.
(2) For those applicants in the post-construction permit stage, wr request that within 30 days of your receipt of this letter, you document by letter your cocaitment to (a) install such systems prior to initial fuel loading and (b) provide the details of the system design in your Final Safety Analysis Report.
(3) For those applicants with applications in the operating license stage of the review prccess, we request that within 30 days of your receipt of this letter, you amend your application to reflect your comaitment to (a. install such systems prior to initial fuel loading and (b) aavise us of your schedule for providing the details of tne system design in your Final Safety Analysis Report.
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I l August 11, Igr78 Because of the relatively large number of plants involved and the similarity of the reactor protection system power supply designs, we anticipate that you, the other af fected applicants, and the General Electric Company may wish to combine efforts in this matter.
In the interest of standardization and minimizing the impact of our review of these systems, we encourage such a combined effort.
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rtoger S. Bbyd, Director Division of Project ManatJe' ment -
Of fice of Nuclear Reactor Regulation f
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Mississippi Power and Light Company cc:
Mr. Robert B. McGehee, Attorney Wise, Carter, Child, Steen &
Caraway P. O. Box 651 Jackson, Mississippi 39205 Troy B. Conner, Jr., Esq.
Conner, Moore & Corber 1747 Pennsylvania Avenue, N. W.
Washington, D. C.
20006 Pechtel Power Corporation ATIN:
T. W. liaberman, Project Engineer Grand Gulf Nuclear Station Gaithersburg, Maryland 20760 1
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