Information Notice 1992-09, Overloading and Subsequent Lock Out of Electrical Buses During Accident Conditions

Overloading and Subsequent Lock Out of Electrical Buses During Accident Conditions

ML031200714
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	01/30/1992
Revision:	0
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-92-009, NUDOCS 9201240235
Download: ML031200714 (3)

UNITED STATESNUCLEAR REGULArORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555January 30, 1992NRC INFORMATION NOTICE 92-09: OVERLOADING AND SUBSEQUENT LOCK OUT OFELECTRICAL BUSES DURING ACCIDENT CONDITIONS

Addressees

All holders of operating licenses 6toJMnstruett0n permits for nuclear powerreactors.92 FEa 13 A8:49

Purpose

The U.S. Nuclear Regulatory Comnission (NRC) is issuing this information noticeto alert addressees to a particular scenario identified by a licensee wherebyelectrical buses could be overloaded during accident conditions, deenergized,and prevented from being reenergized. It is expected that recipients willreview the Information for applicability to their facilities and consideractions, as appropriate, to avoid similar problems. However, suggestionscontained in this information notice are not NRC requirements; therefore, nospecific action or written response is required.

Description of Circumstances

On November 21, 1991, the Power Authority for the State of New York, thelicensee for Indian Point Nuclear Generating Unit 3, reported that the vitalbuses could bWcome overloaded during a loss-of-coolant-accident (LOCA) as aresult of emergency operating procedures directing operators to restore non-essential loads to the buses if offsite power is not lost. The procedure wouldresult in both emergency and non-emergency loads being powered concurrentlyfrom the same bus. The licensee's recent calculations reveal that performingthis procedure could have overloaded buses. The resulting overcurrent conditioncould lock out a bus (i.e., deenergize the bus and prevent it from beingreenergized from any source including the associated emergency diesel generator).DiscussionA LOCA is generally analyzed as the most limiting condition in power demand foronsite electrical systems. When non-essential loads are added to the powersystem under this most demanding condition, electrical buses and breakers couldbe overloaded. The electrical protection system recognizes such an overloadedcondition as an electrical fault on a bus and locks out the bus. The dc-poweredbreaker controls retain the faulted condition, and the emergency diesel generatorwill not be able to energize the bus until protective relays are manuallyreset. The scenario could result in disabling redundant trains of safety-relatedequipment.9201240235 p* WI

IN 92-09January 30, 1992 This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation (NRR) project manager.o &DbecDivision of Operational Events Assessmentoffice of Nuclear Reactor RegulationTechnical contact: Thomas Koshy(301) 504-1176

List of Recently Issued NRC Information Notices

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____-9 rAttachmentIN 92-09January 30, 1992 LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to92-0892-0792-0642-0592-0492-0392-0292-0191-87Revised Protective ActionGuidance for Nuclear Inci-dentsRapid Flow-Induced Erosion/Corrosion of Feedwater PipingReliability of ATWS Mitiga-tion System and Other NRCRequired Equipment NotControlled by Plant Tech-nical SpecificationsPotential Coil InsulationBreakdcwn in ABB RXMH2 RelaysPotter & Brumfield ModelMDR Rotary Relay FailuresRemote Trip FunctionFailures in General ElectricF-Frame Molded-Case CircuitBreakersRelapS/Mod3 Computer CodeError Associated with theConservation of EnergyEquationCable Damage Caused byInadequate Cable Installa-tion Procedures and ControlsHydrogen Etbrittlement ofRaychem Cryofit Couplings01/23/9201/09/9201/15/9201/08/9201/06/9201/06/9201/03/9201/03/9212/27/91All fuel cycle and materi-als licensees authorizedto possess large quanti-ties of radioactive materi-ial.All holders of OLs or CPsfor pressurized waterreactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.L a Operating LicenseP a Construction Permit