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
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-92-009, NUDOCS 9201240235
Download: ML031200714 (3)

UNITED STATES NUCLEAR REGULArORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 January 30, 1992 NRC INFORMATION

NOTICE 92-09: OVERLOADING

AND SUBSEQUENT

LOCK OUT OF ELECTRICAL

Addressees

All holders of operating

licenses 6toJMnstruett0n

permits for nuclear power reactors.92 FEa 13 A8:49

Purpose

The U.S. Nuclear Regulatory

Comnission (NRC) is issuing this information

notice to alert addressees

to a particular

scenario identified

by a licensee whereby electrical

buses could be overloaded

during accident conditions, deenergized, and prevented

from being reenergized.

It is expected that recipients

will review the Information

for applicability

to their facilities

and consider actions, as appropriate, to avoid similar problems.

However, suggestions

contained

in this information

notice are not NRC requirements;

therefore, no specific action or written response is required.Description

of Circumstances

On November 21, 1991, the Power Authority

for the State of New York, the licensee for Indian Point Nuclear Generating

Unit 3, reported that the vital buses could bWcome overloaded

during a loss-of-coolant-accident (LOCA) as a result of emergency

operating

procedures

directing

operators

to restore non-essential

loads to the buses if offsite power is not lost. The procedure

would result in both emergency

and non-emergency

loads being powered concurrently

from the same bus. The licensee's

recent calculations

reveal that performing

this procedure

could have overloaded

buses. The resulting

overcurrent

condition could lock out a bus (i.e., deenergize

the bus and prevent it from being reenergized

from any source including

the associated

emergency

diesel generator).

Discussion

A LOCA is generally

analyzed as the most limiting condition

in power demand for onsite electrical

systems. When non-essential

loads are added to the power system under this most demanding

condition, electrical

buses and breakers could be overloaded.

The electrical

protection

system recognizes

such an overloaded

condition

as an electrical

fault on a bus and locks out the bus. The dc-powered

breaker controls retain the faulted condition, and the emergency

diesel generator will not be able to energize the bus until protective

relays are manually reset. The scenario could result in disabling

redundant

trains of safety-related

equipment.

9201240235 p* WI

IN 92-09 January 30, 1992 This information

notice requires no specific action or written response.

If you have any questions

about the information

in this notice, please contact the technical

contact listed below or the appropriate

Office of Nuclear Reactor Regulation (NRR) project manager.o &Dbec Division of Operational

Events Assessment

office of Nuclear Reactor Regulation

Technical

contact: Thomas Koshy (301) 504-1176 Attachment:

List of Recently Issued NRC Information

Notices

---

____-9 r Attachment

IN 92-09 January 30, 1992 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 92-08 92-07 92-06 42-05 92-04 92-03 92-02 92-01 91-87 Revised Protective

Action Guidance for Nuclear Inci-dents Rapid Flow-Induced

Erosion/Corrosion

of Feedwater

Piping Reliability

of ATWS Mitiga-tion System and Other NRC Required Equipment

Not Controlled

by Plant Tech-nical Specifications

Potential

Coil Insulation

Breakdcwn

in ABB RXMH2 Relays Potter & Brumfield

Model MDR Rotary Relay Failures Remote Trip Function Failures in General Electric F-Frame Molded-Case

Circuit Breakers RelapS/Mod3 Computer Code Error Associated

with the Conservation

of Energy Equation Cable Damage Caused by Inadequate

Cable Installa-tion Procedures

and Controls Hydrogen Etbrittlement

of Raychem Cryofit Couplings 01/23/92 01/09/92 01/15/92 01/08/92 01/06/92 01/06/92 01/03/92 01/03/92 12/27/91 All fuel cycle and materi-als licensees

authorized

to possess large quanti-ties of radioactive

materi-ial.All holders of OLs or CPs for pressurized

water reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.L a Operating

License P a Construction

Permit