Information Notice 1986-49, Age/Enviroment Induced Electrical Cable Failures

Age/Enviroment Induced Electrical Cable Failures

ML031220698
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, Skagit, Marble Hill, Crane
Issue date:	06/16/1986
From:	Jordan E NRC/IE
To:
References
IN-86-049, NUDOCS 8606120767
Download: ML031220698 (4)

LIS ORIGINAL

SSINS No.: 6835 IN 86-49

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C.

20555

June 16, 1986

IE INFORMATION NOTICE NO. 86-49:

AGE/ENVIRONMENT INDUCED ELECTRICAL

Addressees

All nuclear power reactor facilities holding an operating license (OL) or a

construction permit (CP).

Purpose

This notice is intended to describe (1) age/environment failures of electrical

cables that have occurred at San Onofre Nuclear Power Plant, Unit 1, and (2)

actions that can be taken to improve in-service cable reliability.

It is

expected that recipients will review the information for applicability to their

facilities and consider actions, if appropriate, for identifying incipient

failures before they occur.

Suggestions contained in this information notice

do not constitute NRC requirements; therefore, no specific action or written

response is required.

Description of Circumstances

On November 21, 1985, San Onofre Unit 1 experienced an incident that was

investigated formally by the NRC and described in NUREG-1190.

Offsite power

was lost when a transformer was tripped by its differential relays because of a

fault in the cable to the Class 1E 4160-V bus.

Further inspection of the

failed cable showed evidence of insulation degradation and arcing between two

phases to the sheath of the cable.

The most likely cause of the cable failure

was determined to be temperature-induced accelerated aging and degradation of

the cable insulation. The source of this heat was a bare high-temperature

(400'F) feedwater line and pipe flange in the immediate vicinity of the cable.

The thermal insulation had been removed from the pipe during previous repair of

a gasket leak and not replaced.

Southern California Edison Company established a special Cable Evaluation Task

Force which has investigated and tested both 4160 and lower voltage cables and

has identified several other degraded cables that also would have failed over

time.

The faulted cable and other cables are being replaced at San Onofre

Unit 1.

8606120767

IN 86-49 June 16, 1986 Discussion:

The November 21, 1985 event and subsequent investigations and inspections at

San Onofre Unit 1 indicated a possible weakness in the surveillance and main- tenance of station electrical cables.

This weakness is characterized by lack

of adequate monitoring of representative electrical circuits to obtain indica- tions of changes in cable characteristics over time that would be indicative of

degraded conditions.

The lessons learned from this incident suggest a need to

determine whether adequate surveillance and maintenance of medium voltage

cables are being performed.

Proper selection and installation of cables is the basic requirement for

assuring reliability.

However, a good understanding of cable characteristics

and the operational and environmental conditions that could affect these

characteristics is a prerequisite for assurance of the long-term reliability of

cable installations.

Cables that provide power to the medium voltage safety

buses are particularly vital components of the plant electrical system.

Many utilities, as well as other industries such as chemical production and

processing, routinely conduct testing of critical cable circuits.

Although

these practices vary, the information obtained from such periodic testing is

used to identify degraded cables and the need for corrective action.

Timely

corrective action for cables that provide power to Class lE buses and other

critical equipment would minimize unnecessary power losses, unplanned shut- downs, and challenges to the safety systems.

The Insulated Cable Engineers Association (ICEA), National Electrical Manu- facturer's Association (NEMA), and Institute of Electrical and Electronic

Engineers (IEEE) have developed standards which address the testing of new and

in-service cables.

These standards include cable tests such as:

insulation

resistance measurements, power factor measurements, and controlled dc overvoltage

(high potential).

It is suggested that the applicable industry standards be

consulted for performing these tests.

Another important facet of the periodic maintenance and testing program for

cable circuits is the walkdown inspection to identify actual or potential

environmental conditions (heat, water, chemicals, etc.) in the immediate

vicinity of the cables that could adversely affect the cable conditions.

IN 86-49 June 16, 1986 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

-wa;

rwJor

Divisi gof Emergency Preparedness

and E1gineering Response

Office of Inspection and Enforcement

Technical Contacts:

Paul Gill, NRR

(301) 492-8423

Vince Thomas, IE

(301) 492-4755 Attachment:

Attachment 1

IN 86-49

June 16, 1986

LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information

Date of

Notice No.

Subject

Issue

Issued to

86-48

86-47

86-46

86-45

86-44

86-43

86-42

86-41 Inadequate Testing Of Boron

6/13/86

Solution Concentration In The

Standby Liquid Control System

Feedwater Transient With

6/9/86

Partial Failure Of The

Reactor Scram System

Improper Cleaning And Decon- 6/12/86 tamination Of Respiratory

Protection Equipment

Potential Falsification Of

6/10/86

Test Reports On Flanges

Manufactured By Golden Gate

Forge And Flange, Inc.

Failure To Follow Procedures 6/10/86

When Working In High Radiation

Areas

Problems With Silver Zeolite 6/10/86 Sampling Of Airborne Radio- iodine

Improper Maintenance Of

6/9/86

Radiation Monitoring Systems

Evaluation Of Questionable

6/9/86

Exposure Readings Of Licensee

Personnel Dosimeters

All BWR facilities

holding an OL or CP

All BWRs and PWRs

facilities holding

an OL or CP

All power reactor

facilities holding

an OL or CP and

fuel fabrication

facilities

All power reactor

facilities holding

an OL or CP and

research and test

facilities

All power reactor

facilities holding

an QL or CP and

research and test

reactors

All power reactor

facilities holding

an OL or CP

All power rector

facilities holding

an OL or CP

All byproduct

material licensees

OL = Operating License

CP = Construction Permit