Information Notice 1994-24, Inadequate Maintenance of Uninterruptible Power Supplies & Inverters

Inadequate Maintenance of Uninterruptible Power Supplies & Inverters

ML031060485
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:	03/24/1994
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-94-024, NUDOCS 9403180068
Download: ML031060485 (9)

- - Q

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 March 24, 1994 NRC INFORMATION NOTICE 94-24: INADEQUATE MAINTENANCE OF UNINTERRUPTIBLE POWER

SUPPLIES AND INVERTERS

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purnose -

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

notice to alert addressees to potential failures of uninterruptible power

supplies and inverters because of inadequate maintenance. 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

Nine Mile Point Nuclear Station Unit 2 (NMP-2)

On August 13, 1991, an internal failure in the main transformer caused a

degraded voltage which resulted in the simultaneous loss of power outputs from

five uninterruptible power supplies. The power outputs from the five power

supplies were lost because of a combination of a wiring problem and the

failure of the internal batteries to supply control power. The five power

supplies provide power to the main control room annunciator system and to

other systems important to safety.

On March 26, 1992, a non-safety-related power supply failed to provide power

to a radiation monitoring cabinet, causing an engineered safety features

actuation. The licensee determined that an output breaker from the power

supply failed to close because grease in the breaker had dried out and

solidified.

Susquehanna Steam Electric Station Unit 1 (SSES-1)

On July 31, 1991, a relay in the switchyard was operated incorrectly, causing

the loss of one of the offsite power sources to the plant. The loss of this

power source, coupled with the failure of one uninterruptible power supply to //

transfer to its backup power supply, resulted in a loss of power to some ac

instrument panels. The power supply failed to transfer because of problems

9403189068 PDA lro

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IN 94-24 March 24, 1994 with the internal batteries. The loss of power to the instrument panels

caused the loss of numerous instruments and control room indications, as well

as some plant support equipment.

Discussion

Uninterruptible power supply units are designed to supply reliable ac power to

their loads. Designs for such power supplies use an inverter to convert dc

power from a battery to ac power. Some designs also provide a rectifier in

combination with the inverter as one unit. The rectifier converts station

power from ac to dc. The inverter then converts either the output of the

rectifier (normal) or power from a battery (backup) from dc to ac. Offsite ac

backs up the inverter ac output through a power transfer device. Direct

current control power for the power supply is developed internally using power

from external power sources. In some designs, back-up control power is

provided by an internal battery bank.

Major contributing factors for the power supply failures at NMP-2 on

August 13, 1991, and March 26, 1992, were inadequate maintenance of the

batteries which supply power to the control logic and inadequate maintenance

of the power supply output breakers respectively. The cause of the failure at

Susquehanna was three failed cells in the power supply battery bank.

The NRC Office for Analysis and Evaluation of Operational Data (AEOD) recently

prepared engineering evaluation AEOD/E93-03, "Electrical Inverter Operating

Experience - 1985 to 1992," December 1993, to assess inverter operating

experience in the nuclear industry over the last 74 years. In the report, the

staff concludes that the number of inverter failures has decreased, but some

problems still warrant attention. Significant findings in the report are as

follows:

(1) Inverter failures are still causing a large number of inadvertent

engineered safety features actuations, reactor trips, and turbine

runbacks.

(2) Component failures are still the predominant root cause of the failures, followed by human error.

(3) The components that failed most frequently were electrolytic capacitors, followed by transformers, silicon-controlled rectifiers, and transfer

switches.

The staff concluded in this report that, based on a review of licensee event

reports, some licensees obtained a marked decrease in the frequency of

electrical inverter failures by (1)providing the inverter units with adequate

cooling and (2) implementing a preventive maintenance program for the inverter

units that periodically replaced selected components. The staff also

concluded that the proper implementation of vendor recommendations for minor

and major maintenance activities would reduce the number of failures because

licensees would frequently identify and replace degraded components before

they failed.

IN 94-24 March 24, 1994 Related Generic Communications

The NRC has issued the following related generic communications: Information

Notice (IN)93-26, "Grease Solidification Causes Molded-Case Circuit Breaker

Failure to Close,* April 7, 1993, and Supplement 1 to IN 93-26, January 31, 1994; IN 91-64, wSite Area Emergency Resulting From a Loss of Non- Class 1E Uninterruptible Power Supplies," October 9, 1991, and Supplement 1 to

IN 91-64, October 7, 1992; IN 88-57, "Potential Loss of Safe Shutdown

Equipment Due to Premature Silicone Controlled Rectifier Failure,"

August 8, 1988; and IN 87-24, "Operational Experience Involving Losses of

Electrical Inverters," June 4, 1987.

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

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: J. G. Ibarra, AEOD

(301) 492-4441 F. S. Ashe, NRR

(301) 504-2785 Attachment:

List of Recently Issued NRC Information Notices

Al

Attachment

IN 94-24 March 24, 1994 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

94-23 Guidance to Hazardous, 02/22/94 All NRC Licensees.

Radioactive and Mixed

Waste Generators on the

Elements of a Waste

Minimization Program

94-22 Fire Endurance and 03/16/94 All holders of OLs or CPs

Ampacity Derating Test for nuclear power reactors.

Results for 3-Hour Fire- Rated Thermo-Lag 330-1 Fire Barriers

Regulatory Requirements 03/18/94 All fuel cycle and materials

when No Operations are licensees.

being Performed

94-20 Common-Cause Failures 03/17/94 All holders of OLs or CPs

due to Inadequate for nuclear power reactors.

Design Control and

Dedication

94-19 Emergency Diesel 03/16/94 All holders of OLs or CPs

Generator Vulnerability for nuclear power reactors.

to Failure from Cold

Fuel Oil

94-18 Accuracy of Motor- 03/16/94 All holders of OLs or CPs

Operated Valve Diag- for nuclear power reactors.

nostic Equipment

(Responses to Sup- plement 5 to Generic

Letter 89-10)

94-17 Strontium-90 Eye Appli- 03/11/94 All U.S. Nuclear Regulatory

cators: Submission of Commission Medical Use

Quality Management Plan Licensees.

(QMP), Calibration, and

Use

OL - Operating License

CP - Construction Permit

IN 94-24 March 24, 1994 Related Generic Communications

The NRC has issued the following related generic communications: Information

Notice (IN)93-26, "Grease Solidification Causes Molded-Case Circuit Breaker

Failure to Close," April 7, 1993, and Supplement 1 to IN 93-26, January 31, 1994; IN 91-64, "Site Area Emergency Resulting From a Loss of Non- Class lE Uninterruptible Power Supplies," October 9, 1991, and Supplement 1 to

IN 91-64, October 7, 1992; IN 88-57, "Potential Loss of Safe Shutdown

Equipment Due to Premature Silicone Controlled Rectifier Failure,"

August 8, 1988; and IN 87-24, "Operational Experience Involving Losses of

Electrical Inverters," June 4, 1987.

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

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Originalsigned by

Bran K. Grimes

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: J. G. Ibarra, AEOD

(301) 492-4441 F. S. Ashe, NRR

(301) 504-2785 Attachment:

List of Recently Issued NRC Information Notices

• 4FF DRFVrfhinU CONCUiRRFNrFC

OFFICE RPB:ADM* OGCB:NRR* ROAB:AEOD* C/ROAB:AEOD* D/DSP:AEOD*

NAME TechEd AJKugler GLanik JRosenthal GHolalan

DATE 01/04/94 01/06/94 01/21/94 01/21/94 01/24/94 n

OFFICE EELB:NRR* C/EELB:NRR* D/DE:NRR* AC/OGCB:NRR* D

NAME EWeiss CHBerlinger MWHodges AJKugler r

DATE 01/27/94 02/22/94 02/24/94 03/04/94 O3//Z/94 DOCUMENT NAME: 94-24. IN

V,_ IN 94-XX

March XX, 1994 The manuals provided by manufacturers give specific maintenance requirements

for particular UPS and inverter equipment. In addition, manufacturers may be

able to give licensees new information that; has been developed since the

manuals were issued, that licensees can usea to improve the design and

maintenance of inverters and UPSs, and thus; reduce the number of failures.

Related Generic Communications

The NRC has issued the following related generic communications: Information

Notice (IN)93-26, 'Grease Solidification Causes Molded-Case Circuit Breaker

Failure to Close,' April 7, 1993 and Supplement 1 to IN 93-26, January 31, 1994; IN 91-64, "Site Area Emergency Resulting From a Loss of Non- Class lE Uninterruptible Power Supplies," October 9, 1991 and Supplement 1 to

IN 91-64, October 7, 1992; IN 88-57, 'Potential Loss of Safe Shutdown

Equipment Due to Premature Silicone Controlled Rectifier Failure,'

August 8, 1988; and IN 87-24, "Operational Experience Involving Losses of

Electrical Inverters,w June 4, 1987.

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

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact(s): J. G. Ibarra, AEOD

(301) 492-4441 F. S. Ashe, NRR

(301) 504-2785 Attachment:

List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

OFFICE RPB:ADM* OGCB:NRR* ROAB:AEOD* C/ROAB:AEOD* D/DSP:AEOD*

KAME TechEd AJKugler GLanik JRosenthal GHolalan

DATE 01/04/94 01/06/94 01/21/94 01/21/94 01/24/94 OFFICE EELB:NRR* C/EELB:NRR* D/DE:NRR* AC/OGCB:NRR D/DORS:NRR

KME EWeiss CHBerlinger MWHodges AJKugler J BKGrimes'*

DATE 01/27/94 02/22/94 02/24/94 03/94N/94 03/ /94 DOCUMEN -AM:-----LK

DOCUMENT NAME: INVEKIEK.IN

IN 94-XX

February XX, 1994 The manuals provided by manufacturers give specific maintenance requirements

for particular pieces of equipment. The manufacturers may also be able to

give licensees new information that has been developed since the manuals were

issued, in order to improve the design and maintenance of inverters and UPSs, and thus reduce the number of failures.

Related Generic Communications

The NRC has issued other generic communications related to this subject.

These generic communications included Information Notice (IN)93-26, "Grease

Solidification Causes Molded-Case Circuit Breaker Failure to Close,' April 7,

1993 and Supplement 1 to IN 93-26, January 31, 1994; IN 91-64, 'Site Area

Emergency Resulting From a Loss of Non-Class lE Uninterruptible Power

Supplies," October 9, 1991 and Supplement 1 to IN 91-64, October 7, 1992;

IN 88-57, Potential Loss of Safe Shutdown Equipment Due to Premature Silicone

Controlled Rectifier Failure," August 8, 1988; and IN 87-24, "Operational

Experience Involving Losses of Electrical Inverters," June 4, 1987.

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

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact(s): Jose Ibarra, AEOD

(301) 492-4441 F. S. Ashe, NRR

(301) 504-2785 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

OFFICE RPB:ADM* OGCB:NRR* ROAB:AEOD* C/ROAB:AEOD* D/DSP:AEOD*

NME TechEd AJKugler GLanik JRosenthal GHolalan

DATE 01/04/94 01/06/94 01/21/94 01/21/94 01/24/94 OFFICE EELB:NRR* C/A LWR A /DE:NRR J AC/OGCB:NRR D/DORS:NRR

NAME EWeiss CH rli er a MWH6g'AJKugler BKGrimes

DATE 01/27/94 02/2Z/94 02/94 0 /94 02/ /94

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WOCUMMN NAME: INVLK ItK .IN

y_ < IN 94-XX

February XX, 1994 The manuals provided by the manufacturer give the specific maintenance

requirements for a particular piece of equipment. The manufacturer may also

be able to give the licensees new information that has been developed since

the manuals were issued, in order to improve the design and maintenance of the

inverters and reduce the number of maintenance-related failures.

Related Generic Communications

The NRC has issued other generic communications related to this subject.

These generic communications included Information Notice (IN)91-64, *Site

Area Emergency Resulting From a Loss of Non-Class IE Uninterruptible Power

Supplies,3 October 9, 1991 and Supplement 1 to IN 91-64, October 7, 1992;

IN 88-57, 'Potential Loss of Safe Shutdown Equipment Due to Premature Silicone

Controlled Rectifier Failure," August 8, 1988; and IN 87-24, "Operational

Experience Involving Losses of Electrical Inverters,' June 4, 1987.

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

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact(s): Jose Ibarra, AEOD

(301) 492-4441 E. W. Weiss, NRR

(301) 504-3264 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

OFFICE RPB:ADM* OGCB:NRR ROAB:AEOD C/DD:EOD

KM TechEd AJKuler e GLanik X JR enthal C Holal~n

DATE 01/04/94 01/06/94 01/1//94 01/11/94 O1/Z't94 OFFICE E C/EELB:NRR D/DE:NRR C/OGCB:NRR D/DORS:NRR

KME EWiss CHBerlinger 4WHodges GHMarcus BKGrimes

DATE / h2794 / /94 / /94 02/ /94 02/ /94 DUCUMENT NAME: INVtK I K. IN

a__j IN 94-XX

February XX, 1994 The manuals provided by the manufacturer give the specific maintenance

requirements for a particular piece of equipment. The manufacturer may also

be able to provide the licensees with new information that has been developed

since the manuals were issued to improve the design and maintenance of the

inverters and reduce the number of maintenance-related failures.

Related Generic Communications

The NRC has previously issued the following generic communications on this

subject:

Information Notice 91-64, Supplement 1, 'Site Area Emergency Resulting From A

Loss of Non-Class IE Uninterruptible Power Supplies," issued October 7, 1992 Information Notice 91-64, "Site Area Emergency Resulting From A Loss Of Non- Class IE Uninterruptible Power Supplies," issued October 9, 1992 Information Notice 88-57, "Potential Loss of Safe Shutdown Equipment Due to

Premature Silicone Controlled Rectifier Failure," issued August 8, 1988 Information Notice 87-24, Operational Experience Involving Losses of

Electrical Inverters," issued June 4, 1987 This information notice requires no specific action or written response. If

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

one of the technical contacts listed below or the appropriate Office of

Nuclear Reactor Regulation (NRR) project manager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contact(s): Jose Ibarra, AEOD

(301) 492-4441

, NRR

(301) 504- Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES

OFFICE RPB:ADM OGCB:NRR ROAB:AEOD C/ROAB:AEOD D/DSP:AEOD

NAME TechEd k AJKugler GLanik JRosenthal GHolalan

DATE 01/ ff94 01/ /94 O1/ /94 01/ /94 01/ /94 OFFICE EELB:NRR C/EELB:NRR D/DE:NRR C/OGCB:NRR D/DORS:NRR

KAE _ CHBerlinger MWHodges GHMarcus BKGrimes

DATE / /94 / /94 / /94 02/ /94 02/ /94 UUtLlUr~trlI NJU". IY.KI ---- r ..

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