NRC Generic Letter 1978-32

NRC Generic Letter 1978-032: Reactor Protection System Power Supplies (Grand Gulf Nuclear Station, Units 1 & 2)

ML031280391
Person / Time
Site:	Grand Gulf
Issue date:	08/11/1978
From:	Boyd R S Office of Nuclear Reactor Regulation
To:
References
GL-78-032
Download: ML031280391 (4)

• -- Di bu.n..., 'EG(, UNITED STATESe -, fNUCLEAR REGULATORY COMMISSION NRC PDR~-,' * -WASHINGTON, D. C. 20555 Local PDRA u : unJLWR 1 FileAugust 11, 1978 D. VassalloJ. Stolzrcckt N. 50416C. Thomasaccket No. 50-416 E. Hyltonand 5-417OELDB. ScottL. Dreher -G-26Mississippi Power and Light CompanyATTN: Mr. N. L. StampleyVice President -Production 7 Lo / 7 E -jP. 0. Box 1640Jackson, Mississippi 39205Gentlemen:SUBJECT: REACTOR PROTECTION SYSTEM POWER SUPPLIES(GRAND GULF NUCLEAR STATION, UNITS 1 & 2)Criterion 2 of the Commission's General Design Criteria (Appendix A to10 CFR Part 50) requires in part that systems important to safety, suchas the reactor protection system, be designed to withstand the effectsof earthquakes. Reactor protection systems are required to be Class IEsystems, hence they are seismic Category I. The normal reactor protectionsystem power supplies for most General Electric Company boiling waterreactor nuclear steam supply systems, except for those utilizing solidstate reactor protection systems, consist of redundant alternating currentmotor-generator sets which are not seismically qualified.During the course of our review of Georgia Power Company's operating licenseapplication for its Edwin I. Hatch Nuclear Plant Unit No. 2 (Docket No.50-366), we questioned the adequacy of the protection afforded the reactorprotection system against possible sustained over-voltage, under-voltage,or underfrequency conditions from the reactor protection system powersupplies. Specifically, we questioned the capability of the reactor pro-tection system power supplies to accommodate the effects of earthquakeswithout jeopardizing the capability of the reactor protection system toto perform its intended safety function.We determined that a sequence of events initiated by an earthquake can bepostulated which could result in damage to the reactor protection systemcomponents with the attendant potential loss of capability to scram theplant. This sequence of events includes (1) the occurrence of an earthquakethat would cause the undetected failure of a voltage sensor, (2) the failureof a motor-generator set resulting in an abnormal output voltage, (3) thepersistence of this abnormal output voltage, undetected by visual observa-t1ons and surveillance testing, for a time sufficient to damage reactorprotection system components, and (4) failure of these components in sucha onanner that results in the loss of-capability to scram the plant.

.-2 -August 11, 1978We, therefore, required that prior to startup following the first scheduledrefueling outage, Georgia Power Company install Class IE systems approvedby us and capable of de-energizing the reactor protection system powersupplies when their output voltages exceed or fall below or their outputfrequencies fall below limits within which the equipment being poweredby the power supplies has been designed and qualified to operate con-tinuously and without degradation. With such systems, the designs of thereactor protection system power supplies will conform to the applicablerequirements of Criterion 2 of Appendix A to 10 CFR Part 50.Consistent with our finding on Hatch Unit 2, we require that all applicantsfor licenses to construct and operate plants utilizing General ElectricCompany boiling water reactor nuclear steam supply systems with non-seismicCategory I alternating current motor-generator sets as the normal reactorprotection system power supplies install Class IE systems approved by usanu capaDle of de-energizing the reactor protection system power supplieswhen their output voltages exceed or fall below or their output frequenciesfall below limits within which the equipment being powered by the powersupplies has been designed and qualified to operate continuously and withoutdegradation.We will implement this requirement as follows:(1) For those applicants with applications in the construction permit stageof the review process, we request that within 30 days of your receiptof this letter, you amend your application to reflect your commitmentto (a) install such systems prior to initial fuel loading and (b)provide the details of the system design in your Final Safety AnalysisReport.(2) For those applicants in the post-construction permit stage, we requestthat within 30 days of your receipt of this letter, you document byletter your commitment to (a) install such systems prior to initialfuel loading and (b) provide the details of the system design in yourFinal Safety Analysis Report.(3) For those applicants with applications in the operating license stageof the review process, we request that within 30 days of your receiptof this letter, you amend your application to reflect your commitmentto (a) install such systems prior to initial fuel loading and (b)advise us of your schedule for providing the details of the systemdesign in your Final Safety Analysis Report.

-3 -August 11, 1978Because of the relatively large number of plants involved and the similarityof the reactor protection system power supply designs, we anticipate thatyou, the other affected applicants, and the General Electric Company may wishto combine efforts in this matter. In the interest of standardization andminimizing the impact of our review of these systems, we encourage such acombined effort.Sincerely,_ ~ /_.-\ -) ,.-,-,Roger S. Bbyd, DirectorDivision of Project Mana'§Wement-'Office of Nuclear Reactor Regulation

.'4'Mississippi Power and LightCompanycc: Mr. Robert B. McGehee, AttorneyWise, Carter, Child, Steen &CarawayP. 0. Box 651Jackson, Mississippi 39205Troy B. Conner, Jr., Esq.Conner, Moore & Corber1747 Pennsylvania Avenue, N. W.Washington, D. C. 20006Bechtel Power CorporationATTN: T. W. Haberman, Project EngineerGrand Gulf Nuclear StationGaithersburg, Maryland 20760