Information Notice 1989-16, Excessive Voltage Drop in DC Systems

Excessive Voltage Drop in DC Systems

ML031180521
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, 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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Crane
Issue date:	02/16/1989
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-89-016, NUDOCS 8902100283
Download: ML031180521 (6)

-

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C.

20555

February 16, 1989

NRC INFORMATION NOTICE NO. 89-16:

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is being provided to alert addressees to potential

problems resulting from unexpected large voltage drops in cables between the

batteries and circuit breakers. 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 do not constitute NRC requirements; therefore, no specific

action or written response is required.

Description of Circumstances

Nine Mile Point Unit 1 was shut down in December 1987 for refueling.

During this

shutdown, the licensee made modifications to its 125-Vdc power system. A sub- sequent review of these modifications led the licensee to conclude that there

was a voltage supply problem associated with the operation of battery charger

(MG set) circuit breakers. The manufacturer of these circuit breakers stated

that the minimum voltage for operation of the circuit breakers was 90 volts.

The technical specifications require a minimum of 106 Vdc at the battery

terminals for the batteries to be considered operable. However, studies showed

that with 114 Vdc at the battery terminals, the calculated voltage at the breaker

would be less than 90 Vdc because of line losses due to current demand during

breaker closure. A battery voltage of less than 114 Vdc could exist at the

time ac emergency power is required to be reconnected to the battery chargers.

Thus, if a loss of site ac power were to occur, the dc voltage at the battery

charger circuit breakers may not be adequate for the battery chargers to be

reconnected to emergency ac power. This situation would cause the batteries to

discharge. The decreasing dc voltage would lead to degraded dc control power

and a subsequent trip of the emergency diesel generators. Therefore, a loss of

normal ac power could lead to a loss of dc power and the subsequent loss of

emergency ac power.

Discussion:

Problems with electrical systems at commercial power reactors have been

identifiedwith increasing frequency. These problems led to the issuance

8902100283 1*}

IN 89-16 February 16, 1989 of Generic Letter 88-15, "Electric Power Systems -

Inadequate Control Over

Design Processes," on September 12, 1988.

The above-described event is a

unique illustration of one of the types of problems presented in the generic

letter.

The Nine Mile Point Unit 1 licensee is not aware of any testing that could be

used to establish the adequacy of the original design, nor has the licensee

found documentation of the original design basis. The voltage drop could be

attributed to an inadequate original estimate of load, hence cable sizing;

load creep over the years without assessment of the consequences; or use today

of a potentially more conservative power profile as determined by current

practice for battery sizing.

After identifying the problem, the licensee

assessed the actual loads and plans to replace the undersized cable to improve

the system's operability.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the technical

contacts listed below or the Regional Administrator of the appropriate regional

office.

aD

rs

D-tvsonruf Operattwnal-Events-AsSEssmjent

Office of Nuclear Reactor Regulation

Technical Contacts: J. Carter, NRR

(301) 492-1194

J. Lazevnick, NRR

(301) 492-0814 Attachment:

List of Recently Issued NRC Information Notices

Attachment

IN 89-16

February 16, 1989 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issuance

Issued to

89-15

89-14

89-13

89-12

Second Reactor Coolant Pump

Shaft Failure at Crystal

River

Inadequate Dedication

Process for Commercial

Grade Components Which

Could Lead to Common Mode

Failure of a Safety System

Alternative Waste Management

Procedures in Case of Denial

of Access to Low-Level Waste

Disposal Sites

Dose Calibrator Quality

Control

Failure-of DC Motor-Operated

Valves to Develop Rated

Torque Because of Improper

Cable Sizing

Undetected Installation

Errors In Main Steam Line

Pipe Tunnel Differential

Temperature-Sensing Elements

at Boiling Water Reactors.

Credit for Control Rods

Without Scram Capability

in the Calculation of the

Shutdown Margin

Pump Damage Caused by

Low-Flow Operation

2/16/89

2/16/89

2/8/89

2/9/89

2/2/89

1/27/89

1/26/89

1/26/89

89-11

All holders of OLs

or CPs for nuclear

power reactors.

All holders of OLs

or CPs for nuclear

power reactors.

All holders of NRC

specific licenses.

All NRC medical

licensees.

All holders of OLs

or CPs for nuclear

power reactors.

All holders of OLs

or CPs for BWRs.

All holders of OLs

or CPs for test and

research reactors.

All holders of OLs

or CPs for nuclear

power reactors.

89-10

89-09

89-08 OL = Operating License

CP = Construction Permit

IN 89-16 February 16, 1989 of Generic Letter 88-15, "Electric Power Systems -

Inadequate Control Over

Design Processes," on September 12, 1988. The above-described event is a

unique illustration of one of the types of problems presented in the generic

letter.

The Nine Mile Point Unit 1 licensee is not aware of any testing that could be

used to establish the adequacy of the original design, nor has the licensee

found documentation of the original design basis. The voltage drop could be

attributed to an inadequate original estimate of load, hence cable sizing;

load creep over the years without assessment of the consequences; or use today

of a potentially more conservative power profile as determined by current

practice for battery sizing. After identifying the problem, the licensee

assessed the actual loads and plans to replace the undersized cable to improve

the system's operability.

No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the technical

contacts listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: J. Carter, NRR

(301) 492-1194

J. Lazevnick, NRR

(301) 492-0814 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS PAGE FOR CONCURRENCE

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2/10/89

2/3/89

2/6/89

2/8/89

2/3/89

2/9/89

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IN 89- February , 1989 The licensee is not aware of any testing that could be used to establish

the adequacy of the original design, nor has the licensee found documentation of

the original design basis. The voltage drop could be attributed to an in- adequate original estimate of load, hence cable sizing, or load creep over the

years without assessment of the consequences, or use today of a potentially more

conservative power profile as determined by current practice for battery sizing.

After identifying the problem, the licensee assessed the actual loads

and plans to replace the undersized cable to improve the system's operability.

No specific action or written response is required by this information

notice. If you have any questions about this matter, please contact a

technical contact listed below or the Regional Administrator of the

appropriate regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

J. Carter, NRR

(301) 492-1194

J. Lazevnick

(301) 492-0814 Attachment:

List of Recently Issued NRC Information Notices

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February , 1989

Page 3 of

No specific action or written response is required by this information

notice.

If you have any questions about this matter, please contact a

technical contact listed below or the Regional Administrator of the

appropriate regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

J. Carter, NRR

(301) 492-1194

J. Lazevnick

(301) 492-0814 Attachment: List of Recently Issued NRC Information Notices

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