Information Notice 1988-89, Degradation of Kapton Electrical Insulation

Degradation of Kapton Electrical Insulation

ML031150053
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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	11/21/1988
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-88-089, NUDOCS 8811150088
Download: ML031150053 (10)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 November 21, 1988 NRC INFORMATION NOTICE NO. 88-89: DEGRADATION OF KAPTON ELECTRICAL INSULATION

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is being provided to alert addressees to a potentially

generic safety problem involving Kapton aromatic polyimide electrical insulation.

Kapton is used extensively in nuclear power plants as wire insulation in con- tainment penetrations and cable entrance seals manufactured by Conax Buffalo

Corporation, and in various insulation systems in products supplied by other

vendors. Kapton is a registered trademark of E. I. du Pont de Nemours and

Company.

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

Problems involving Kapton insulation have been reported at nuclear power plants

and elsewhere as described below. The most significant event identified in the

nuclear industry occurred at San Onofre Unit 1.

San Onofre Nuclear Generating Station Unit 1 On June 15, 1987 Southern California Edison Company advised the NRC of a problem

involving damaged Kapton insulation on containment electrical penetration as- semblies at San Onofre Unit 1. During electrical testing of control rod drive

equipment circuits to determine if previous cooling fan malfunctions had caused

any damage, unacceptably low insulation resistances were found on 35 circuits.

In one penetration assembly alone, 11 circuits tested below one megohm and 11 others below 100 megohms. The licensee then visually inspected the approxi- mately 5000 penetration leads in the plant, and discovered nicked insulation

in 52 cables covering close to 200 circuits. Most of the defects were outside

containment; 15 nicked leads were inside containment.

00z1 11 rrwo

/

i

IN 88-89 November 21, 1988 Laboratory analysis of two damaged leads showed no signs of electrically induced

damage, and the insulation edges at the breaks were smooth (suggesting moderate

chemical attack). The damage sites were highly localized; adjacent insulation

showed no degradation. The copper conductor was oxidized considerably.

As a short-term corrective action, the licensee replaced all safety-related

wires showing any signs of degradation or. damage. Longer-term corrective

action, now partially completed, includes provision of cable tray covers;

replacement of nicked non-safety-related cables; and administrative and

procedural measures such as personnel training and written precautions

concerning unprotected Kapton-insulated wires. This event is described

in Licensee Event Report 05000205 87-008-00, dated July 10, 1987.

The licensee attributed the damage primarily to physical damage (cuts, punc- tures, abrasions) to exposed Kapton insulation, mainly during installation of

the replacement penetration assemblies in 1985-86. Some damage was attributed

to subsequent stepping on the wires and placing or dropping objects on them.

Once the Kapton insulation was penetrated, condensation of marine air on the

outside containment pigtails provided a conductive path that lowered insulation

resistances. The extensive replacement of containment electrical penetration

assemblies such as occurred at San Onofre Unit 1 is uncommon, and it contributed to

the exposure of unprotected Kapton leads to mechanical damage. Exposure of the

Kapton leads to an outside marine atmosphere is also unusual.

Other Kapton Concerns

(1) Information Notice 87-08 (reference 1) describes 1986 failures of motorized

valve operators because wires insulated with Kapton/Teflon and Nomex short- circuited. The Kapton/Teflon was a 0.0012-inch tape overlapped 50-percent.

These wires were subjected to abrasion damage during wiring of the valve

operators.

(2) Information Notice 87-16 (reference 2) describes 1987 degradation of Kapton

diaphragms in pressure switches caused by chemical attack by ammonia con- tained in the process fluid.

(3) In 1984 Gulf States Utilities filed a 10 CFR 50.55(e) report concerning

a short circuit between two Kapton-insulated wires from Conax penetration

assemblies at River Bend Station Unit 1. The condition occurred during

plant construction, and inspection showed 15 of 201 conductors to have

nicked or otherwise damaged insulation. Investigation showed that degra- dation was generally attributable to scuffs, gashes, and related damage

aggravated by the presence of water.

(4) In several instances anomalies have occurred during qualification type

testing of Kapton-insulated pigtail wires on Conax products or on other

equipment such as transmitters that had cable entrances sealed by Conax

seals. The anomalies have been attributed to handling and stresses not

typical of plant installations; e.g., shipment from a radiation test

facility to a steam test facility. Only a few wires showed degradation

in each instance, whereas multiple wires not subject to abnormal handling

have successfully completed type test sequences.

IN 88-89 November 21, 1988 (5) In response to Information Notices 87-08 and 87-16, du Pont wrote to the

NRC to caution that when Kapton is used in nuclear power plants where

environmental qualification is required, engineered designs which protect

Kapton from direct exposure to loss of coolant accident sprays are required.

This is because Kapton tends to degrade when exposed to high temperature

steam or to certain volatile chemicals such as sodium hydroxide.

(6) The Naval Research Laboratory (NRL) has published or presented several

papers (references 3, 4) describing failures of Kapton-insulated wires

during laboratory testing. The Navy has carefully examined potential

problems with Naval aircraft service. As a result, The Navy intends to

stop buying aircraft using Kapton-insulated wire, and the other military

services are studying possible implementation of restrictions.

The NRL work, in conjunction with other available information, shows that

Kapton wire insulation is subject to damage by four mechanisms:

O Mechanical nicking or gouging can expose a wire conductor. Low in- sulation resistance can occur if an electrical path to an adjacent

metallic conductor is formed by either a conductive solution or

direct metal-to-metal contact. The San Onofre Unit 1 event is of

this type.

O Direct chemical attack by strong alkaline solution can dissolve

Kapton. This process would be of concern only if Kapton were

installed contrary to Conax installation instructions in plants

with sodium hydroxide spray, so that the Kapton was either exposed

to prolonged direct spray impingement or prolonged soaking in spray

solution.

O Bullets or projectiles can damage energized wire bundles. This is

not likely in commercial power plants, and related safety concerns

are minimal because of the redundancy and separation used for safety- related equipment.

o A complex hydrolytic Kapton degradation process has been identified

with synergistic, non-linear dependence on temperature, moisture, and

mechanical strain. Test data from 60 degrees Celsius upward show a

reciprocal logarithmic temperature dependence. du Pont (reference 5)

has suggested a fifth-power humidity dependence. Wolf (reference 6)

reported a strong dependence on strain and postulated a minimum strain

of 3 to 4 percent below which degradation does not occur. The process

is almost fully reversible provided that actual cracking has not oc- curred. Review of commercial nuclear power plant applications indi- cates that this mechanism is not significant for either normal or

accident conditions; operating experience and type test results sup- port this conclusion. However, violation of minimum bend radius

requirements specified by Conax and Rosemount for their wires, combined with significant moisture exposure and elevated temperatures, could produce this type of damage.

IN 88-89 November 21, 1988 du Pont has several publications describing Kapton and its use. These may be

obtained by contacting:

Mr. Paul Wyche

E. I. du Pont Nemours and Company, Inc.

External Affairs Department N-2526 Wilmington, Delaware 19898 Phone: (302) 774-1942 Conax Seals

The major safety-related use of Kapton in commercial nuclear power plants is

in Conax products: containment electrical penetration assemblies, penetration

replacement adapter module assemblies, electrical conductor seal assemblies

(ECSAs), PL-type gland seals, and resistance temperature detector assemblies.

Conax uses Kapton-insulated wire constructed of two wraps of type FN Kapton

film, spiral wrapped in opposite directions. Since the film consists of 0.001 inch of Kapton sandwiched between two 0.0005-inch-layers of Teflon (a du Pont

trademark for FEP fluorocarbon), and each wrap is overlapped 50-percent, the

total insulation thickness is 0.008 inch. The MIL-W-81381/11 wire used by the

Navy is similar except that it has a 0.002-inch dispersed Kapton topcoat.

For seal assemblies, Conax supplies a heat-shrinkable polyolefin jacket to me- chanically protect Kapton insulation. In addition, installation manuals caution

against mechanical damage and protective conduit is also specified. Penetration

assemblies are supplied with a junction box which encloses Kapton leads. Most

other vendors using Kapton-insulated leads in safety-related applications pro- vide covers or enclosures (for example, Rosemount seals and Target Rock and

Valcor solenoid valves).

Discussion:

Despite the plant-specific aspects of the San Onofre Unit 1 event, the generic

lesson is that the performance of numerous Kapton-insulated wires degraded con- siderably after only one year in a quite mild environment. Mechanical damage

to Kapton insulation combined with exposure to condensation of moist salty air

produced unacceptable degradation of the electrical insulation properties.

Although Kapton-insulated pigtails have successfully completed several accident

qualification type tests, the test specimens are believed to have been free from

nicks in the insulation; further, test anomalies occurred in some cases in which

the pigtails were subjected to abnormal handling. The lesson is that preaccident

damage can lead to failure of Kapton-insulated wires during or after accidents.

Addressees

are alerted that the following conditions may breach the integrity of

Kapton insulation, leading to possible failures under either normal or accident

conditions:

(1) Mechanical damage such as nicks, cuts, abrasion, or sharp bending combined

with exposure to moisture.

(2) Prolonged contact with alkaline solutions.

IN 88-89 November 21, 1988

Addressees

are also reminded that excessive handling of wiring is undesirable.

In view of the industry's generally good operating experience with Kapton, addressees may elect to take actions in response to the information in this

notice by beginning with review of procedures and designs to determine whether

the conditions cited above may exist. Caution with any future maintenance or

installation activity involving Kapton is important.

Virtually all commercial nuclear power plants contain Kapton-insulated wires

in safety and non-safety-related applications, with Conax products used most

extensively. Such components as containment electrical penetration assemblies

and cable entrance seals are commonly used in Class lE circuits and in applica- tions requiring qualification to 10 CFR 50.49. Failure of Kapton insulation

during either normal plant operation or accident conditions could render asso- ciated equipment inoperable.

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

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

contact listed below or the Regional Administrator of the appropriate regional

office.

.T 19A-%

harles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Richard C. Wilson, NRR

(301) 492-0997 Attachments:

1. References

2. List of Recently Issued NRC Information Notices

i

Attachment 1 IN 88-89 November 21, 1988 REFERENCES

1. IE Information Notice No. 87-08: "Degraded Motor Leads in Limitorque dc

Motor Operators," February 4, 1987

2. IE Information Notice No. 87-16: "Degradation of Static "0" Ring Pressure

Switches," April 2, 1987.

3. F. J. Campbell, "Temperature Dependence of Hydrolysis of Polyimide Wire

Insulation," IEEE Transactionson Electrical Insulation, Vol. EI-20 No. 1, February 1985.

4. A. M. Bruning, 'Predictive Life Measurements of Naval Aircraft Wiring,"

Proceedings: Workshop on Power Plant Cable Condition Monitoring, EPRI

EL/NP/CS-5914SR, July 1988.

5. J. 0. Punderson and J. F. Heacock, "Polyimide Film Insulation for Aerospace

Wire and Cable: Why Long-Term Performance Exceeds Some Limited Laboratory

Projections, " presented at the 34th International Wire and Cable Symposium, Cherry Hill, NJ, November 19-21, 1985 (available from du Pont).

6. C. J. Wolf, D. L. Fanter, and R. S. Soloman, "Environmental Degradation of

Aromatic Polyimide-Insulated Electrical Wire," IEEE Transactions on

Electrical Insulation, Vol. EI-19 No. 4, August 1984.

Attachment 2 IN 88-89 November 21, 1988 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

88-88 Degradation of Westinghouse 11/16/88 All holders of OLs

ARD Relays or CPs for nuclear

power reactors.

88-87 Pump Wear and Foreign 11/16/88 All holders of OLs

Objects in Plant Piping or CPs for nuclear

Systems power reactors.86-106, Feedwater Line Break 11/10/88 All holders of OLs

Supp. 3 or CPs for nuclear

power reactors.

88-86 Operating with Multiple 10/21/88 All holders of OLs

Grounds in Direct Current or CPs for nuclear

Distribution Systems power reactors.

88-85 Broken Retaining Block 10/14/88 All holders of OLs

Studs on Anchor Darling or CPs for nuclear

Check Valves power reactors.

88-84 Defective Motor Shaft 10/20/88 All holders of OLs

Keys in Limitorque Motor or CPs for nuclear

Actuators power reactors.

88-83 Inadequate Testing of Relay 10/19/88 All holders of OLs

Contacts in Safety-Related or CPs for nuclear

Logic Systems power reactors.

88-82 Torus Shells with Corrosion 10/14/88 All holders of OLs

and Degraded Coatings in or CPs for BWRs.

BWR Containments

88-81 Failure of Amp Window 10/7/88 All holders of OLs

Indent Kynar Splices or CPs for nuclear

and Thomas and Betts power, test, and

Nylon Wire Caps During research reactors.

Environmental Quali- fication Testing

88-80 Unexpected Piping Movement 10/7/88 All holders of OLs

Attributed to Thermal or CPs for PWRs.

Stratification

OL = Operating License

CP = Construction Permit

IN 88-89 November 21, 1988

Addressees

are also reminded that excessive handling of wiring is undesirable.

In view of the industry's generally good operating experience with Kapton, addressees may elect to take actions in response to the information in this

notice by beginning with review of procedures and designs to determine whether

the conditions cited above may exist. Caution with any future maintenance or

installation activity involving Kapton is important.

Virtually all commercial nuclear power plants contain Kapton-insulated wires

in safety and non-safety-related applications, with Conax products used most

extensively. Such components as containment electrical penetration assemblies

and cable entrance seals are commonly used in Class 1E circuits and in applica- tions requiring qualification to 10 CFR 50.49. Failure of Kapton insulation

during either normal plant operation or accident conditions could render asso- ciated equipment inoperable.

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

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

contact 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

Richard C. Wilson, NRR

(301) 492-0997 Attachments:

1. References

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE PAGE.

• RPB:ARM

TechEd*

a7 /10/25/88 OFC :VIB:DRIS:NRR :VIB:DRIS:NRR :C:VIB:DRIS:NRR:D:DRIS:NRR :C:OGCB:DOEA :D:DOEA:NRRR:

NAME :RCWilson:mgc* :UPotapovs* :EWBrach* :BKGrimes* :CHBerlinger*  : ossi

DATE :11/02/88 :11/02/88  : 11/02/88  : 11/05/88 :11/10/88 :11//Jq88

IN 88- November , 1988 Virtually all commercial nuclear power plants contain Kapton-insulated wires

in safety and non-safety-related applications, with Conax products used most

extensively. Such components as containment electrical penetration assemblies

and cable entrance seals are commonly used in Class 1E circuits and in applica- tions requiring qualification to 10 CFR 50.49. Failure of Kapton insulation

during either normal plant operation or accident conditions could render asso- ciated equipment inoperable.

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

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

contact listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessments

Office of Nuclear Reactor Regulation

Richard C. Wilson, NRR

(301) 492-0997 Attachments:

1. References

2. Recently Issued NRC Information Notices

• Transmitted by dated _

• SEE PREVIOUS CONCURRENCE PAGE.

, RPB:ARM

pen TechEd*

A~ 10/25/88 OFC :VIB:DRIS:NRR :VIB:DRIS:NRR :C:VIB:DRIS:NRR:D:DRIS:NRR :C:OGCB:DOEA :D:DOEA:fNFR :

---

_-----_-----__-_ ____

__ __ __ __-_ __ __ _ __ ____________

NAME :RCWilson:mgc* :UPotapovs* :EWBrach* :BKGrimes* :CHBerlinger :CERossi

-______ _________-_____-________-_____-______________-___-__________ _______________-_______-__

DATE :11/02/88 :11/02/88  : 11/02/88 11/05/88 :l1//O/88  : / /88

IN 88- November 1988 Virtuallv all commercial nuclear power plants contain Kapton-insulate wires

in safety and non-safety-related applications, with Conax products ed most

extensivel Such components as containment electrical penetrati assemblies

and cable ent ance seals are commonly used in Class 1E circuits nd in applica- tions requirin qualification to 10 CFR 50.49. Failure of Ka on insulation

during either noal plant operation or accident conditions ould render asso- ciated safety-rel ted equipment inoperable.

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

If you have any quest'ons about this matter, please ntact the technical

contact listed below o the Regional Administrator f the appropriate regional

office.

r\harle E. Rnosi_ Diretnr

Dlvi on of Operational Events Assessments

Off ce of Nuclear Reactor Regulation

Richi NRR

(301:

Attachments:

1. References

2. Recently Issued NRC Inf ationINoti es

• Transmitted by dated

RPB: ARM

TechEd

12tkg

to/Zt88 OFC :VIB:DP S:NRR :VIB:DRIS:NRR (:C:VI D_

WS:NRR:D:D :C:OGCB:DOEA :D:DOEA:NRR

---

-

--

a-------

---

^----------- A--:--------------:------

-p-v- NAME :RCW son:mgc P :UPotapovs :B :CHBerlinger :CERossi

DATE :l /2/88 :11/2./88  :// 88 :1(/5/88  : / /88 4/ /88

1"/3 I