Information Notice 1991-68, Careful Planning Significantly Reduces the Potential Adverse Impacts of Loss of Offsite Power Events During Shutdown

Careful Planning Significantly Reduces the Potential Adverse Impacts of Loss of Offsite Power Events During Shutdown
	ML031190482
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:	10/28/1991
From:	Rossi C; Office of Nuclear Reactor Regulation
To:	;
References
	IN-91-068, NUDOCS 9110230028
	Download: ML031190482 (11)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 October 28, 1991

'NRC INFORMATION NOTICE 91-68: CAREFUL PLANNING SIGNIFICANTLY REDUCES

THE POTENTIAL ADVERSE IMPACTS OF LOSS

OF OFFSITE POWER EVENTS DURING SHUTDOWN

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice

to describe the positive benefits that were derived by two licensees when their

outage activities were carefully planned, scheduled, and performed. These

licensees did not rely solely on technical specifications to identify the

minimum equipment that should be available under various shutdown configura- tions. Rather, these licensees made additional equipment available and devel- oped special procedures, as appropriate, to mitigate the consequences that

could result from forced equipment outages. It is expected that recipients

will review the information for applicability to their facilities and consider

appropriate actions. However, suggestions contained in this information notice

are not NRC requirements; therefore, no specific action or written response is

required.

Description of Circumstances

In November 1990, the licensee for the Turkey Point Plant began an 11-month

dual unit outage to conduct a major electrical system upgrade including

installing two additional emergency diesel generators (EDGs). On

March 13, 1991, while both units were defueled and the safety-related EDGs were

inoperable, offsite power for Unit 4 was being provided through the startup

transformer. Spent fuel pool cooling pumps were being powered from the

"C" load center which was being supplied by the "A"vital bus. Electrical

power for the component cooling water (CCW) pumps and the intake cooling water

(ICW) pumps was being provided from vital bus "A". At the time, spent fuel

pool cooling was the most significant nuclear safety function.

An alternate source of power supply to the CCW, ICW, and spent fuel pool

cooling pumps was available from four, non-safety-related (black start) diesel

generators. Other backup sources of power to the pumps included interconnec- tion with the Unit 3 startup transformer and transfer to another Unit 4 trans- former (after defeating circuit breaker interlocks). An alternate method of

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IN 91-68 October 28, 1991 spent fuel pool cooling, which was available, involved the use of a trailer- mounted diesel generator and a diesel powered fire pump or a non-safety grade

screen wash pump. Detailed procedures for use of the alternative cooling

methods were'available.

At 3:30 p.m., a lockout occurred on the Unit 4 startup transformer resulting in

a total loss of all vital AC power to Unit 4. A notification of an unusual

event (NOUE) was declared as a result of the loss of vital offsite power. The

licensee manually started, but did not load, two of the black start diesel

generators. The other black start diesel generators were not started. All of

these sources were available to supply power to the cooling pumps for the spent

fuel pool if the startup transformer could not be returned to service.

The licensee inspected the startup transformer and associated circuit breakers

and found no electrical fault indications. At 4:35 p.m., the licensee ener- gized the startup transformer. At 5:27 p.m., power was restored to the CCW,

ICW and spent fuel pool cooling pumps and forced cooling to the spent fuel pool

was resumed. The NOUE was then terminated. The temperature of the spent fuel

pool had increased from 840 F to 87°F during the 2-hour duration of the event.

On March 20, 1991, another event of interest occurred at the Indian Point

Station. Before the event, Indian Point, Unit 2, (IP2) was in cold shutdown

with all fuel removed from the vessel and stored in the spent fuel pit.

Indian Point, -Unit 3, (IP3) was operating-at 100 percent power An a normal

plant configuration. At 7:15 p.m., a potential transformer on a 345kV bus

section at a remote substation failed catastrophically, creating a ground fault

on the 345kV system. Fault isolation circuitry opened the main generator

output breaker for IP3, which initiated a reactor trip. The reactor trip was

uncomplicated and offsite power to IP3 vital buses was not interrupted.

However, an explosion and subsequent fire in the substation caused circuit

breakers to electrically isolate the 138kV feeder circuit supplying offsite

power to the IP2 6.9kV buses. As a result, the 6.9kV non-vital and 480V vital

buses that were in service were deenergized. EDG 23 started automatically on

bus undervoltage. At the time, the other two IP2 EDGs were tagged out of

service for maintenance. As designed, EDG 23 did not load to the buses because

all logic requirements for automatic loading were not satisfied. EDG 23 was

manually loaded to two vital 480V buses. This action allowed a service water

pump and a component cooling water pump to be started, a battery charger to be

placed in service, and lighting to the auxiliary and containment buildings to

be restored.

At the time of the event, offsite power to some vital loads was being supplied

directly from temporary connections from an Indian Point Unit 1 feeder bus as

opposed to being supplied from normal sources. These loads included the spent

fuel pit cooling pump, the auxiliary building exhaust fan, and a battery

charger. The licensee established these temporary connections to mitigate the

consequences of a potential loss of the normal offsite source.

Since two EDGs were out of service, a temporary EDG was started as a precau- tion. However, the unit was not needed during the event. The licensee had

K)

IN 91-68 October 28, 1991 imported this temporary EDG unit to the site specifically for use as an alter- nate onsite source of emergency power during the shutdown In view of the

significant number of planned equipment outages. The licensee provided this

unit even though there were three gas turbines and a second 138kV feeder that

were available from off site and that could have been manually aligned to

energize the IP2 vital buses.

The licensee restored normal offsite power to IP2 within 30 minutes. During

the event, component cooling water and service water were lost for only

2 minutes limiting the interruption to spent fuel cooling.

Discussion

These events illustrate the benefits of carefully planning equipment outages

during shutdown. Before each event, the licensees had made additional power

sources available to augment normal supplies. Furthermore, the licensees had

developed written procedures to address anticipated equipment failures. These

efforts allowed operating personnel to have adequate time to perform deliber- ate, well Informed actions and minimized the safety concerns associated with

each event. If the licensees had been less careful in their planning, these

events could have been more significant. The technical specifications allow

licensees considerable flexibility in removing equipment from service and

altering normal system lineups during shutdown.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please call the

technical contact listed below or the appropriate Office of Nuclear Reactor

Regulation (NRR) project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 492-1173 Attachment: List of Recently Issued NRC Information Notices

C

0

I:IECAC

9- Attachment

IN 91-68 to October 28, 1991

9- Page I of I

CA

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

C

U),

0I .

Information Date of

Notice No. Subject Issuance Issued to

CI" a

If~ 90-51. Failures of Voltage-Dropping 10/24/91 All holders of OLs or CPs

C

z Supp. I Resistors in the Power for nuclear power reactors.

co

F) 91-67 Supply Circuitry of Electric

Governor Systems

Problems With the Reliable 10/21/91 All holders of OLs or CPs

(

Detection of Intergranular for pressurized-water reactors.

Attack (IGA) of Stem

Generator Tubing

91-66 (1) Erroneous Data in 10/18/91 All fuel cycle licensees, ONuclear Safety Guide critical mass licensees, TID-7016, Revision 2,' interim spent fuel storage

(NUREG/CR-O095, ORNL/ licensees, and all holders

NUREG/CSD-6 (1978)) and of operating licenses or

(2) Thermal Scattering construction permits for

Data Limitation in the test, research, and nuclear

Cross-Section Sets Provided power reactors.

with the KENO and SCALE Codes

91-65 Emergency Access to 10/16/91 All NRC licensees.

Low-Level Radioactive

waste Disposal Facilities

91-64 Site Area Emergency 10/09/91 All holders of OLs or CPs

Resulting From a Loss for nuclear power reactors.

of Non-Class IE

Uninterruptible Power Supplies

91-63 Natural Gas Hazards

at Fort St. Vramn

Nuclear Generating Station

ID/03/91 All holders of OLs or CPs

for nuclear power reactors. C

91-62 Diesel Engine Damage 09/30/91 All holders of OLs or CPs

Caused by Hydraulic for nuclear power reactors.

Lockup Resulting from

Fluid Leakage Into

Cylinders

OL

Operating License

CP

Construction Permit

go"at

I

IN 91-68 October 28, 1991 imported this temporary EDG unit to the site specifically for use as an alter- nate onsite source of emergency power during the shutdown in view of the

significant number of planned equipment outages. The licensee provided this

unit even though there were three gas turbines and a second 138kV feeder that

were available from off site and that could have been manually aligned to

energize the IP2 vital buses.

The licensee restored normal offsite power to IP2 within 30 minutes. During

the event, component cooling water and service water were lost for only

2 minutes limiting the interruption to spent fuel cooling.

Discussion

These events illustrate the benefits of carefully planning equipment outages

during shutdown. Before each event, the licensees had made additional power

sources available to augment normal supplies. Furthermore, the licensees had

developed written procedures to address anticipated equipment failures. These

efforts allowed operating personnel to have adequate time to perform deliber- ate, well informed actions and minimized the safety concerns associated with

each event. If the licensees had been less careful in their planning, these

events could have been more significant. The technical specifications allow

licensees considerable flexibility in removing equipment from service and

altering normal system lineups during shutdown.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please call the

technical contact listed below or the appropriate Office of Nuclear Reactor

Regulation (NRR) project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical contact: N. Fields, NRR

(301) 492-1173 Attachment: List of Recently Issued NRC Information Notices

See previous concurrence Document Name: IN 9168 OFC :*EAB:NRR :*TECH ED :*SC:EAB:NRR :*C:SELB:NRR :*C:EAB:NRR :*C:DRPE:NRR :

____

___ _ _ _-----_--__-: - ------------ __ ____ _ __

NAME :NFields :JMain :DFischer :FRosa :AChaffee :SVarga

DATE :08/28/91 :08/28/91 :08/29/91 :09/06/91 :10/07/91 :10/18/91 :

OFC : *RI : *RII :*C:OGCB:NRR :*DD:DST:NRR :D:DOEA:NRR :

NAME : CHehl : LReyes :CBerlinger :GHolahan

DATE : 10/11/91 : 10/11/91 :10/17/91 :10/21/91 :/O/I4W91 :

- f

IN 91-XX

November XX, 1991 unit even though there were three gas turbines and a second 138kV feeder that

were available from off site and that could have been manually aligned to

energize the IP2 vital buses.

The licensee restored normal offsite power to IP2 within 30 minutes. During

the event, component cooling water, and service water was lost for only 2 minutes limiting the interruption to spent fuel cooling.

Discussion

These events illustrate the benefits of carefully planning equipment outages

during shutdown. Before each event, the licensees had made additional power

sources available to augment normal supplies. Furthermore, the licensees had

developed written procedures to address anticipated equipment failures. These

efforts allowed operating personnel to have adequate time to perform deliberate, well informed actions and minimized the safety concerns associated with each

event. If the licensees had been less circumspect in their planning, these

events could have been more significant. The Technical Specifications allow

licensees considerable flexibility in removing equipment from service and

altering normal system lineups during shutdown.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please call the

technical contact listed below or the appropriate Office of Nuclear Reactor

Regulation project manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contact:

N. Fields, NRR

(301) 492-1173 Attachment: List of Recently Issued NRC Information Notices

See previous concurrence

OFC :*EAB:NRR :*TECH ED :*SC:EAB:NRR :*C:SELB:NRR :*C:EAB:NRR :*C:DRPE:NRR

_ _-- _ --_____

__ __ _-- ---- -- _-_-_:

_ _ _:_ _ -------

NAME :NFields :JMain :DFischer :FRosa :AChaffee :SVarga

__ ___ ___

__ -------

DATE :08/28/91 :08/28/91 :08/29/91 :09/06/91 :10/07/91 :10/18/91 A/

OFC : *RI : *RII :*C:OGCB:NIR D5 :NRR :D:DOEA:NRR :

NAME : CHehl : LReyes :CBerlinger ( olahan :CRossi :

DATE :10/11/91 :10/11/91 :10/17/91 ;bLt/91 ://91 :

OFFICIAL RECORD COPY

Document Name: IN/TURKEY PT. & INDIAN PT.