NUREG/CR-5461, Forwards Draft NUREG/CR-5461, Aging Assessment of Cables, Connectors & Electrical Penetration Assemblies Used in Nuclear Power Plants

Forwards Draft NUREG/CR-5461, Aging Assessment of Cables, Connectors & Electrical Penetration Assemblies Used in Nuclear Power Plants

ML20248H692
Person / Time
Issue date:	10/04/1989
From:	Farmer W NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
To:	John Thomas EQUIPMENT QUALIFICATION ADVISORY GROUP
References
CON-FIN-A-1818, RTR-NUREG-CR-5461 NUDOCS 8910120007
Download: ML20248H692 (72)

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y e c h 'o,, UNITED STATES n . NUCLEAR REGULATORY COMMISSION g e WASHINGTON, D. C. 2%55

• • • ++ OCT pl 1989 Mr.. James E. Thomas

' Chair, EQAG.

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. Duke Power Company

'422' South. church Street P.O. Box 33189 Charlotte, NC 28242

Subject:

. Utility: Review of NRC Draft Report NUREG/CR-5461 on, "An Aging Assessment of Cables,-Connectors, and Electrical' Penetration Assemblies Used'in Nuclear Power -.

Plants"'

Enclosed for your review and comment is a draft of the final phase I aging report on the assessment of cables, connectors and electrical penetrations. Any comments the EQAG utility review group would like considered should be sent to me by November 9, 1989. ,

Sincerely, NW.W William S. Farmer, Program Manager Electrical & Mechanical Engr. Br.

Office of Nuclear Regulatory Research ,

Enclosure:

As stated cc w/ encl:

A. Marion, NUMARC G. Sliter, EPRI

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NUREG/CR-5461 SAND 89-2369 RV AN AGING ASSESSMENT OF CABLES, CONNECTORS, AND ELECTRICAL PENETRATION ASSEMBLIES USED IN NUCLEAR POWER PLAhTS Mark J. Jacobus  !

Printed: December,1989 Sandia National Laboratories Albuquerque,NM 87185 '

Operated by Sandia Corporation for tfie U.S. Department of Energy Prepared for Division of Engineering Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington,DC 20555 Under Memorandum of Understanding 40-550-75 NRC FIN No. A 1818 DRAFT i

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Abstract This report examines aging effects on cables, connectors, and electrical penetration assemblies (EPAs). Aging is defined as the cumulative effects that occur with the passage of time to a component. If unchecked, these effects may lead to a loss of function and an impairment of safety. This study includes a review of component usai;e in nuclear power plants; a review of some commonly used components and their materials of construction; a review of the stressors that the components might be exposed to in both normal and accident environments; a connilation and evaluation ofindustry failure data; a discussion of component failure mo,d es and causes; and a brief description of current industry testing and mamtenance practices.

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_.g 4 Table of Contents P. ige EXECUTIVE S U M MARY.................................................. .......... .......... .. ............ I 1.0 INTR ODU CTI O N... ... ... ......... ......... ............. ................... ...... . . .......... 3 1.1 Scope.................................................................................................. 4 2.0 APPLICATIONS AND FEATURES OF EQUIPMENT IN NUCLEAR PO WE R PLANTS .......... .... . ... . ........ ................. ..... ..... .................... .. 5 2.1 Cables.......................................................................................... 5 2.2 Connectors........................................................................................ '5 23 Ele ctrical Pe n e trations................................................................. ......... .. 6

3.0 DESCRIPTION

S OF COMMONLY USED COMPONENTS...................... 8 3.1 In t rod u cti o n ... ............... ..... .... ...... .............. ............................. ..................... 8

' 3.2 Cables............................................................................................................ 8 3.2.1 - Rockbestos Multiconductor Firewall III XLPE Cable ........... 8 3.2.2 Rockbestos Firewall Coaxial Cable .... ..................................... 8 3.23 Okonite FMR Multiconductor Control Cab 1e ....... ... ......... 9 3.2.4 Okonite Okolon Single Conductor Power and Control Cab 1e..................................................................................... 9 3.2.5 - Anaconda Flame-Guard FR-E.P Multiconductor Control Cable..................................................................................... 9 3.2.6 Samuel Moore Dekoron Dekorad Instrument Cable.. ......... 9 3.2.7 Brand Rex Ultrol Power and Control Cable............................ 10 3.2.8 Ol d e r Cabl e Type s '............................ ................................... ..... 10-3.2.9 Oth e r Cabl e Type s . .................. ....... ........................................ 10 33 Connectors............................................................................................ 10 33.1 Te rmi n al B l ocks ....... ... .......................................... . ........... . 10 33.2 Splices........................................................................................... 11 3.4 Ele ctrical Pe netrations................. ........................... ............ .... ...... .... 14 3.4.1 D.G.O'Brien........................................................................... 15 3.4.2 Conax........................................................................................ 18 3.43 Westingh ou se ......................... ........................... .......... ..... .... 22 4.0 STRESSORS AND AGING MECHANISMS.......... . ......... ............ ........ 24 4.1 Normal Environme nts Aging .................................................. .... .... ..... 24 4.1.1 Cab 1es.......................................-..........................................24 l 4.1.2 Co nn e ct o rs .................................. ................ ............... ..... .......... 27 4.13 El e ctrical Pe n e trations ................ ............................................... 28

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4.2 Abnormal Environments Stressors ........................................................... 29 4.2.1 Cables.....................................................................................29 4.2.2 Conne ct o rs ............. ...................................... . ..... .......... .......... 30 4.2.3 Electrical Penetrations ............. ............................. ................... 31 5.0 - EVALUATION OF FAILURE DATA.... ...................... . ............ ... ....... 34 5.1 In t rod u cti o n ................................ ................... ........... .. ............... ......... 34 5.2 Cables...............................................................................................34 5.3 Connectors............................................................................................ 36 5.4 Ele ctrical Pen e trations............ .............. ...... ......... ............................... 38 6.0 FAILURE MODE AND CAUSE ANALYSIS... ........ ..................... .... ...... 40 6.1 Cables........................................................................................ 40 6.2 Conneetors........................................................................................ 41 6.3 El e ettical Pe n etrations.................. ..... ...................... ....c......... . ..... 42 7.0 TESTIN G AND MAINTEN AN CE..... ................. ....................... ................... 43 8.0 CON DITI ON M ONITO RIN G.............................................................................. 44 8.1 Sandia NPAR Phase II Program ............................... .............................. 44 8.2 Other Condition Monitoring Activities.................................................... 46 9.0 CO N CLU S I O N S ...................... .. ........................ . . ...................... ...... .... ........ ..... 48 10.0 RE FE R EN CES ........................ .. ............. . ......................... ...... ... .......................... 49 APPENDI X A Cable Eve nts .................................... ........................................... ..... 53 APPENDIX B Connection Eve nts .. ................................................ ............ ............ 58 APPENDIX C E PA Eve nts ..................................................................... ........ ........... 64

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List of Ficures

-East Figure 1 Generic One-Piece and Sectional Terminal Blocks........ ................... 12 Figure 2 Sample Raychem Installations Over Crimp:d Connection and Bol t ed Connection......... ................................ ....... ... ....... ........... 13 Figure 3 Typical Mounting, of D. G. O'Brien EPA ............... .................. ........... 15 Figure 4 Schematic of Typical D. G. O'Brien Module .......................................... 16 Figure 5 Inboard Mating Plu i; of D. G. O'Brien Connector............... .... ......... 17 Figure 6 of D. G. O'Brien Connector ................... ....... 18 Figure 7 Outboard Mating P;ul;Conax Schematic Diagram o EPA and One Module ........................... 19 Figure 8 Conax EPA Mounting Methods ..................... ...................... ................. 20 Figure 9 Details of Conax EPA Construction.... .... . . .. .... . 21 Figure 10 Westinghouse Modular EPA ........................ .... .................. .. .. ... 22 Figure 11 Typical Module for a Westinghouse Modular EPA.................. . . 23 '

Figure 12 Typical Westinghouse EPA Installation ........... .. ... .... . . ........ 23 1

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c .. .e List of Tables East Table 1 Cable Products Included Phase Il Tes't Program.................. .................. 7-Table 2 - Most Popular In-Containment Cable Manufacturers........... ..... .......... 9 Table 3 Most Popular Terminal Block Manufacturers ... ....... ... ........... 11 Table 4 E PA S u ppli e rs .......... ................. ....... ....... .............. ... .. ....... .............. 14 Table 5 Analysis of Cable LER Events (mid.1980 to 1988)..... .... .................... 35 Table 6 Estimate of Cable Failure Rate...... ... ................... ........................ ...... 36 Table 7 Number of LERs per Calender Year... ................................. ...... ......... 36 Table 8 Analysis of Connection LER Events (mid-1980 to 1988) ... ................ 37 Table 9 Number of LERs per Calender Year .............. ......... ............ ........ .. . 38 Table 10 Analysis of EPA Eve n ts ................ .... ......................................... ......... 39 Table 11 Estimated Failure Rate of EPAs in Normal Senice ............................... 39 Table 12 Plants and Components Included in University of Conn e cticu t S t u dy.................................. .................................. ................ 46

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EXECUTIVE

SUMMARY

This report examines aging effects on cables, connectors, and electrical penetration assemblies EPAs). In this report, aging is defined as the cumulative effects that occur with e passage of time to a component. If unchecked, these effects may lead to a loss of function and an impairment of safety.

Cables, connectors, and electrical penetration assemblies (EPAs) are used l

extensively throughout all nuclear power plants. Cables and connectors are used in I

every electrical circuit in the plant; EPAs are included in every circuit which is inside contamment.

The NRC-sponsored aging assessment of cables, connectors, and penetrations is broken into two phases, defined by the standard Nuclear Plant Aging Research (NPA,R) approach.1 The first phase consists of evaluation of usage, operating experience, current inspection and surveillance methods, and applicable literature.

This report details the results of Phase I.

Included in this study is a review of component usage in nuclear power plants; a review of some commonly used components and their materials of construction; a review of the stressors that the components might be exposed to in both normal and accident environments; a compilation and evaluation of industry failure data; a discussion of component failure modes and causes; a description of current industry testing and maintenance practices; and a review of some monitoring techniques that might be useful for monitoring the condition of these components.

The conclusions of the study are as follows:

a) Cables, connections, and EPAs are highly reliable devices under normal plant operations, with no evidence of significant failure increases with aging. Consequently:

1) they receive little or no preventative maintenance.

2) the most significant aging affects are those that have the potential to cause common mode failures during accident conditions.

b) Many of the accident failure modes of cables, connections, and EPAs normal operation because of the absence of would noteratures be detected during,dities. The most important failure mode is and humi high temp shorting (or reduced electrical isolation). Several different causes may result in this failure mode.

c) Plant operational experience is useful to the extent that it may indicate some possible accelerated degradation mechanisms for cables, connections, and EPAs that could lead to common mode failure under off-normal environmental conditions. However, current LER data provides a very limited database for this purpose.

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' d) A significant number of manufacturers have produced cables, connections, and EPAs, resultint,in many different materials and construction methods.

Consequently, generic assessments of aging effects and vulnerabilities -

become much more difficult.

An NRC-sponsored Phase II experimental assessment for cables is currently ~

underway at Sandia National Laboratories and will be documented in a future report.

At this time, connections and EPAs are excluded from the Phase II efforts.

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1.0 INTRODUCTION

For purposes of this report, aging is defined as the cumulative effects that occur with the passage of time to a component. If unchecked, these effects may lead to a loss of function and an impairment of safety. However,it must be kept in mind that not all aging effects will necessarily lead to failure. The actual results of aging effects will be appbcation dependent.

Cables, connectors, and electrical penetration assemblies (EPAs) are used extensively throughout all nuclear power plants. Cables and connectors are used in every electrical circuit in the plant; EPAs are included in every circuit which is inside containment. Thus, the safety signi5cance of these components is unquestionable.

Because of their safety significance, all of these components have been the subject of extensive research and mdustry tests. Many of these tests have been equipment qualification (EO) tests, or are closely related to EO. In fact, the question of aging is closely related to EO,1 although the emphasis is slightly different. The fundamental EO concern is that of common me.dc failure of equipment, with an emphasis on exposure to adverse environmental conditions (e.g. steam, high dose rate radiation, pressure, temperature, and chemical spray). Thus, any EO test failure that can be demonstrated to be a " random" failure may generally be discounted. Aging, on the other hand, is further concerned with random failures and how to predict and prevent increased age related random and common mode failures through maintenance and surveillance programs.

Cables, connectors, and EPAs are much more reliable than the components that they are normally increases connected (several to (perhap)s hundred percent m random ,byfailure several ratesorders of magnitude).

of this equipment will Thus, have little impact on overall plant risk. It is thus evident that under the current level of operating experience, the only possible aging threat is when increased component vulnerabihty (resulting from age related degradation) is combined with a harsh environment exposure. These are the only conditions where the failure rate could become significant enou,;h to impact overall plant risk. Consequently,ironmentalthis r emphasizes common moc e failures that might occur during accident env conditions, particularly any failure modes that could be aggravated by prior age-related degradation. With this emphasis, most equipment that is located outside containment will not be subjected to accident conditions nearly as severe as corresponding ec{uipment inside containment, and thus we will focus largely on inside containment equipment. However, for connections and cables that are typically used only outside containment, some consideration will be given to the harsh environments outside containment.

The aging assessment of cables, connectors, and penetrations is broken into two j phases, defined by the standard NPAR approac3.1 The first phase consists of evaluation of usage, operating experience, current inspection and surveillance '

methods, and appheable literature. This report details the results of Phase I. The second phase, already underway at Sandia, consists of experimental assessments of cables commonly used in safety applications in nuclear power plants.2,3 Connections and EPAs are not included m Phase II. Surveillance and condition monitoring techniques have been reviewed and discussed in work by others4,5 and a number of l

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e4 them are being assessed experimentally in the Phase II study. Section 8.0 of this report provides a description of some condition monitoring methods that might be applicable to cables, connections, and EPAs.

1.1 Scops The scope of the NPAR Phase I study is to assess cables, connectors, and EPAs. We will limit most discussions to safety related equipment that is required to be environmentally qualified. As noted m the introduction, particular emphasis will be placed on inside containment applications since these are exposed to the most severe environmental conditions in most accident situations. However, outside containment applications will be considered where a particular type of component is only used there.

2.0 APPLICATIONS AND FEATURES OF EQUIPMENT IN NUCLEAR POWER PIANTS 2.1 Cables For purposes of the following discussions, cable will categorized as low voltage power, medium and high voltage power, control, and instrumentation. Medium and

.aigh voltage power cables are almost non-existent where the circuits must operate under harsh environmental conditions. Thus, they will not be included further in the discussions.1.ow voltage power circuits that might be exposed to harsh environments  !

j are typically used to power 480 V and smaller motors, such as on motor-operated j

valves (MOVs). Control circuits that might be exposed to harsh environments i typically include solenoid valves, motor-operator control circuitry, and various types I of switches. Instrumentation circuitry that might be exposed to harsh environments includes pressure, level, and flow transmitters, resistive temperature detectors (RTDs), t aermocouples, and radiation monitors.

ical cable insulations are ethylene propylene rubber (EPR), cross linked po ethylene (XLPE), and silicone rubber (SR). Some lants have cables insulated wi polyvinyl chloride (PVC), polyethylene ( E), butyl rubber (BR),

chlorosulfonated polyethylene (CSPE or Hypalon), or pton. Typical jackets are neoorene and hypalon, with some plants having PVC, chlorinated polyethylene (CP E), or fiberglass braid for jackets.

Cables may be either single conductor (with or without a jacket) or multiconductor with a jacket. Jackets are typically intended for cable protection during installation, but they are also sometimes relied upon for protecting the underlying insulation from beta radiation during accident conditions.

Table 1 is a list of the cables being used in the Phase.II NPAR study of cables. These represent a reasonable cross section of cables (in terms of materials and construction) used for safety-related applications in nuclear plants. Although a

" generic cable" is difficult to define, a 3 conductor,12 AWG power and control cable or a 2 conductor, twisted shielded pair,16 AWG instrumentation cable are two constructions which are perhaps the most popular in the industry, based on information obtained through NRC EO inspections which Sandia has participated in.

The most popular insulations are XLPE and EPR and the most popular jackets are CSPE and Neoprene.o 2.2 Connectors The most common types of connections used in nuclear safety-related applications are splices (butt or bolted), crimp-type ring lugs, and and terminal blocks. Splices and lugs may be insulated or uninsulated. Some splices are covered with tape (often Okonite or Scotch) or heat shrink tubing (usually Raychem) when used in potentially harsh environments. Construction of butt splices is quite simple, consisting of a metal barrel slightly larger than the conductor to be connected with an optiona'l insulation which might be composed of Nylon or Kynar. Bolted splices are similarly simple.

Terminal blocks are used throughout plants in many low voltage power (less than 480 V), control, and instrumentation app ications. In response to EQ concerns such as those outlined in Information Notice 84-47, a number of plants have removed either

1 I all inside containment terminal blocks in safety circuits or all inside containment terminal blocks in instrumentation circuits. Terminal blocks provide a convenient, low-cost method of connecting cables. They are especially convenient where access to equipment leads is necessary for maintenance or calibration.

Another tyx of connections that have become more common in recent years as EO concerns aave heightened is conduit seals. They are used (primarily inside containment) as a moisture barrier between the inside of a conduit and the mside of a cornponent (since the conduits are normally vented to the environment through a junction box). These seals are essentially very small electrical penetrations; hence, the discussions for EPAs are generally applicable throughout this report.

Coaxial connections are in limited use in safety related circuits in harsh emironment areas; the most critical application (in terms of required function) is for radiation monitoring circuits, where very high insulation resistance may be required during accident conditions.

Other types of connections are used in nuclear plants, such as thermocouple connectors, but they are less popular and are generally specialized connections.

They will not be specifically considered in this report.

2.3 Electrical Penetrations EPAs arovide access to the reactor containment interior for all electrical power, contro , and instrumentation required for normal reactor operation. Further, it is necessary that the EPA maintains an air tight barrier to the elevated temperature and pressure of release products resulting from accident conditions so that any release products will be confm' ed to the reactor containment.

EPA designs have evolved with the growth of commercial nuclear electric power generating stations. As a consequence, there is a large variety of EPAs, fabricated by a number of companies, currently installed in existmg power plants./ EPA design concepts include field manufactured units, factory assembled multiple conductor canister designs, and single or multiple conductor modular units w:lich are then assembled into a retaining fixture or header plate to complete the EPA unit.

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Table 1 Cable Products Included Phase II Test Program Supplier Description Brand Rex XLPE Insulation, CSPE Jacket,12 AWG, 3/C, 600.V Rockbestos Firewall 3, Irradiation XI.PE, Neoprene Jacket,12 AWG,3/C,600 V

Raychem Flamtrol, XLPE Insulation,12 AWG,1/C,600 V -

Samuel Moore Dekoron Polyset, XLPO Insulation, CSPE Jacket,12 AWG,3/C and Drain -

Anaconda Anaconda Y Flame-Guard FR-EP EPR Insulation, CPE Jacket,12 AWG,3/C,600 V Okonite Okonite Okolon, EPR Insulation, Hypalon Jacket,12 AWG,1/C, 600 V Samuel Moore Dekoron Dekorad Type 1952, EPDM Insulation, Hypalon Jacket,16 AWG,2/C TSP,600 V Kerite Kerite 1977, FR Insulation, FR Jacket,12 AWG 1/C,600 V Rockbestos RSS-6-104/LE Coaxial Cable,22 AWG,1/C Shielded Rockbestos Firewall Silicone Rubber Insulation,16 AWG,1/C,600 V Champlain Polyimide Insulation, Unjacketed,12 AWG,1/C BIW . Bostrad 7E, EPR Insulation, CSPE Jacket,16 AWG,2/C TSP,600 V

Abbreviations used in table:

XLPE- Cross linked polyethylene CSPE - Chlorosulfonated polyethylene AWG - American Wire Gauge

/C- number of conductors XLPO-Cross-linked polyolefin FR-EP - Flame retard ant ethylene propylene CPE- Chlorinated polyethylene EPR -Et lene propylene rubber EPDM - ene aropylene diene monomer 15P -Twist shie' ded pair FR - Flame retardant BIW - BostonInsulated Wire

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3.0 DESCR1ITIONS OF COMMONLY USED COMPONENTS 3.1 Introduction In this section, the design of the various components will be reviewed. Because of the

r. umber of different manufacturers and types of equipment, only certain equipment wiU be described here. The equipment selected for desenption is based on the following criteria:

a) Equipment that tends to be most common as judged by previous surveys and NRC EO inspections that Sandia has participated in.

b) equip, ment that tends to be representative of other equipment that is not desenbed.

The equipment chosen for description here does not reflect any views as to the suitability of components for use in nuclear pou :r plants.

3.2 Cables Based on Sandia experience with NRC EQ inspections and the Equipment Qualification Data Bank (EODB), over 30 different manufacturers have been identified that have supplied cable to the nuclear industry for safety related applications. A complete list of cable manufacturers supplying in-containment cables may be found in Reference 6. Based on Reference 6, the most popular in-containment cables, as determined by the number of entries in the EQDIk (i.e. not based on installed footage), are given in Table 2. It should be noted that Anaconda and Continental and that Rockbestos and Cerro represent the same manufacturers at different points in time.

3.2.1 Rockbestos Multiconductor FirewallIII XLPE Cable l Rockbestos Firewall III XLFE is a XI.PE-insulated cable that is normally supplied with a flame-retardant Neo >rene or Hypalon jacket. The XLPE compound may be either irradiation cross-linied or chemically cross-linked. This power and control cable is available in standard sizes from 9 AWG to 18 AWG and from 2 to 19 conductors.- The voltage ratings are 600 or 1000 V. Standard insulation thickness is 25 or 30 mils with jackets from 45-80 mils. Continuous conductor rated temperature is 90*C, The cable is certified to applicable standards which include the aging, accident, and flame spread requirements of IEEE 323-1974 and IEEE 383-1974.

3.2.2 Rockbestos Firewall Coaxial Cable Rockbestos Firewall Coaxial cable is available in coaxial, triaxial, or twinaxial configurations. A thin insulation made of a hard 3olymer designated "LE"is applied to the conductor. A radiation cross-linked modified polyolefin forms the pnmary insulation. The jacket is radiation cross-linked, flame retardant, non-corrosive modified polyolefin. The different configurations are rated for at least 1000 V and use different configurations use different size conductors and different insulation thicknesses. The ca )le is rated at 90* C and is certified to applicable standards which include the aging, accident, and fiame spread requirements of IEEE 323-1974 and IEEE 383-1974.

l Table 2 Most Popular In-Containment Cable Manufacturers 6

1. Rockbestos

2. Okonite

3. Boston Insulated Wire

4. Kerite  !

5. Anaconda

6. Brand Rex

7. Raychem

8. Samuel Moore

9. Cerro

10. Continental 3.23 Okonite FMR Multiconductor Control Cable Okonite FMR control cable is an EPR-insulated cable that is supplied with a vulcanized CSPE jacket. This control cable is available in standard sizes . rom 9 AWG to 18 AWG (also suitable for low power applications) and from 2 to 19 conductors.

The voltage ratings are 600 or 2000 V. Standard insulation thickness is 30 or 45 mils with jackets from 45-80 mils. Continuous conductor rated temperature is 90* C. The cable is certified to applicable standards which include the aging, accident, and flame spread requirements of IEEE 323-1974 and IEEE 383-1974.

3.2.4 Okonite Okolon Single Conductor Power and Control Cable Okonite Okolon single conductor control cable uses a composite insulation of EPR and CSPE. This cable is available in standard siies from 14 AWG to 1000 kemil (thousand circular mils). The voltage ratings is 600 V. Composite insulation thickness is 45 to 145 mils. Continuous conductor rated temperature is 90*C. The cable is certified to applicable standards which include the aging, accident, and flame spread requirements of IEEE 323-1974 and IEEE 383-1974.

3.2.5 Anaconda Flame-Guard FR-EP Multiconductor Control Cable Anaconda Flame-Guard FR-EP control cable is an EPR-insulated cable that is supplied whh a chlorinated polyethylene (CPE) jacket. This control cable is available in standard sizes from 10 AWG to 14 AWG (also suitable for low power applications) and from 2 to 19 conductors. The voltage ratings is 600 V. Standard insulation thickness is 30 mils with jackets from 45-80 mils. Continuous conductor rated temperature is 90' C. The cable is certified to applicable standards which include the agin , accident, and flame spread requirements of IEEE 323-1974 and IEEE 383- 74.

3.2.6 Samuel Moore Dekoron Dekorad Instrument Cable Dekoron Dekorad instrument cable Type 1952/1962 is an ethylene propylene diene monomer (EPDM)-insulated cable that is supplied with a CSPE jacket on each conductor and an overall CSPE jacket. The standard size cable is 16 AWG twisted, shielded pair rated at 600 V. Standard insulation thickness is 20 mils with a primary 9

insulation jacket of 10 mils and an overall jacket of 45 mils. Continuous conductor rated temperature is 90* C. The cable is certified to applicable standards which include the aging, accident, and flame spread requirements of IEEE 323-1974 and IEEE 383-1974.

3.2.7 Brand Rex Ultrol Power and Control Cable Brand Rex Ultrol Power and Control Cable is an irradiation XLPE-insulated cable that is supplied with a CSPE or Neoprene jacket. This cable is available in standard sizes from 9 AWG to 20 AWG and from 2 to 37 conductors. De voltage rating is 600 V. Standard insulation thickness is 25 or 30 mils with jackets from 45-110 mils.

Continuous conductor rated temperature is 90' C. The cable is certified to applicable standards which include the aging, accident, and flame spread requirements of IEEE 323-1974 and IEEE 383-1974.

3.2.8 Older Cable Types Older and/or less used cable types include those employing silicone rubber, butyl rubber, or po ethylene insulatmn. Silicone rubber is used for high temperature service (usuall where radiation doses are relatively) low). A few plan Engineering. Rockbestos is apparently the only manufacturer currently producing silicone rub >er for safety-related inside containment applications. The soft msulation is vulnerable to local damage and some silicone rubber is prone to radiation damage.

These reasons have limited the application of silicone rubber in nuclear plants.

Very little butyl rubber and polyethylene, if any, is still used in containment EO applications because they are both vulnerable to radiation damage at the levels postulated for accident conditions in typical reactors containments. However, it is still used for a few outside containment applications 3.2.9 Other Cable Types Many cable products in addition to those mentioned above are used in nuclear power plants. A few of the more popular ones include Rockbestos Pyrotrol; Okonite Okoprene and VFR; Anaconda Flameguard and Durasheath; Samuel Moore Elastoset and Polyset; Kerite FR, FR3, and HTK; Raychem Flamtrol; Brand Rex Ultrol; General Electric Vulkene and Vulkene Supreme; and ITf' Exane II.

3.3 Connectors Since the maior types of connections used in nuclear power plants are terminal blocks and splices, the discussion here will be limited to these items. Many conduit seals are constructed very much like an electrical penetration and will therefore not be discussed further. Connectors, such as the Namco EC210 series, will also not be discussed because they are used somewhat less than terminal blocks and splices.

3.3.1 TerminalBlocks An extensive terminal block evaluation program was conducted at Sandia.8,9 Included in the report is a review of termma: block usage in the nuclear power

a industry; terminal block design, manufacture, selection, procurement, installation, inspection and maintenance; and terminal block quality assurance practices.

Based on the usage review,9 Table 3 lists the most common terminal block manufacturers based on the number of plants identified as having the given manufacturer's terminal blocks. The data is not complete, but it does give some indication of relative usage. A total of 16 different manufacturers is identified in Reference 9.

l Table 3 Most Popular Terminal Block Manufacturers 9

1. General Electric

2. Weidmuller

3. Buchanan

4. Marathon

5. States

6. Westinghouse

7. Square D The most common terminal block material identified in Reference 9 was phenolic i with either a glass or cellulose filler, with lesser usage of alkyd, melamine, diallyl phthalate, and nylon. Terminal block design is relatively simple and is generally of two types, either one-piece or sectional. In a one-piece design, the base structure is the insulating material and it is molded as a single piece which includes the barriers between terminals. Connection terminals are attached to the block, with the number of terminals governed by the one piece design. A sectional design is only slightly more complicated. Each terminal is an individually molded insulator (with metal terminal added) which is mounted to a common metal rail, thus allowing the block to have a variable number of terminals up to the limit of the rail. Figure I shows generic one-piece and sectional constructions.

Terminal blocks are normally installed in junction boxes for phy"sical and environmental protection. Most junction boxes contain a "weephole to allow condensed moisture to drain from the enclosure and to allow pressure equalization in the event of an environmental pressure excursion.

Individual terminal block characteristics differ primarily in size, detailed shape,

. However, they also tend to be much material, andofdesign,(sectional alike because or requ their simple functional onegiece)irements and design. Because of thI similarities and the generic discussions here and in References 8 and 9, detailed j descriptions of individual blocks will not be given.

1 3.3.2 Splices The fundamental designs of butt splices, crimp-type ring lu,gs, and bolt splices are even simpler than that of a terminal block. Butt splices are simply a circular piece of l metal whose ends may be crimped to a conductor. Crimp, type rmg lugs are the same l l

as a butt splice on one end, but the,y have a ring connection at the other end, which might be used to connect to a ternunal block. Bolted splices normally consist of two l

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crimp type rinJ ugs l (which may have more than one ring) that tre bolted together).

An example o a bolted connection using 2 ring lugs that each have 2 rings is shown in Figure 2(b). The connection is shown covered with Raychem beat shrink tubing.

Butt splices and ring lugs may be covered by some type of insulation, typically nylon or Kynar. In many cases, splices are covered by a beat shrinkable covering or tape.

For qualified applications, the major current supplier of heat shrink tubing is Raychem. Okomte and Scotch produce tapes that have been qualified for certain applications.

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" shim" may be added to the smaller wire. Figure 2 shows two example Raychem installations. Note the use of shims in both mstallations. Raychem heat shrink tubing is certified to applicable standards which include the aging, accident, and flame spread requirements of IEEE 323-1974 and IEEE 3831974. The material was tested for 40, year operation at 90' C and is rated at 1000 V. Installation of Raychem beat shrink is governed by a thorough procedure for selection, cable preparation, shrinking, and inspection.

Okonite insulating tape, model T-95, is intended for splicing and terminations in nuclear environments. It is an ethylene-propylene based thermosetting compound, rated at 90* C. It has been tested to ]EEE 383-1974 requirements for nuclear applications. Installation practices are important when using a tape splice and detailed procedures are avai) able for this purpose.

h 3.4 Electrical Penetrations There is a large, variety of EPA's, fabricated by a number of companies, currently installed in existmg power plants. EPA design concepts include field manufactured units, factory assembled multiple conductor canister designs, and single or multiple i conductor modular units which are then assembled into a retaining fixture or header ]

plate to complete the EPA unit. Of the considerable number of EPA fabricators, j only three, CONAX, D. G. O'Brien, and Westinghouse, currently supply EPAs. A j measure of the diversity of installed EPAs and manufacturers may be obtained from Table 4 which is a fairly recent compilation of both active and former EPA suppliers.7 Column 2 of the table EPA's installed) was obtained from the Southwest Research Institute Equipment Reh(ability Data Bank (circa 1982). The sea column refers to the insulating barrier material through which the electrical conductors penetrate the EPA. The exact composition of any particular sealant / insulation compound is often proprietary information. Those EPA's without seal material information probably were field fabricated units with very limited information available.

Table 4 EPA Suppliers Supplier EPAs Installed Sul Material CONAX 213 Polysulfone O'Brien 258 Metal-Glass i Westinghouse 178 Epoxy The following are no longer in production:

Amphenol 360 . Epoxy '

Chi. Br. & Iron 744 Crouse-Hinds 104 Epoxy EBASCO 50 General Electric 301 Epoxy Physical Sci.'s 64 Metal-Glass VIKING 404 Metal-Glass The EPAs manufactured offsight are mounted in nozzles (steel tubes) fabricated into the containment wall. Depending on the EPA / nozzle design, the EPA and nozzle may be mated by one of two methods--either by bolts or by a continuous weld. In the case of attachment with bolts, gasket or O-ring seals are used to insure an impervious seal at the mating flange surfaces. Seal materials include metals, plated metals, and ethylene propylene and other polymer base rubbers. In general, provision is made to allow monitoring of the seal mteg,rity by observing the gas pressure in the region between the adjacent gaskets /O-nngs m the mating flanges. Weldable EPA's are attached to containment structure nozzles by means of a continuous weld between integral) weld ring. EPAs ma the containment at either the inboar EPA (d (reactor) or outboard containment nozzle and Attachment side.y at thebe attached 4

outboard location offers some additional EPA protection in the event of an accident and may also facilitate installation and maintenance / surveillance activities.

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All EPAs - Beld fabricated, canister, and modular - are designed to hermetically seal and electrically isolate all of the electrical conductors on bota the inner (reactor side) and outer sides of the penetration. Depending on the manufacturer and EPA design, the EPA may provide for monitoring the internal pressure of a nonreactive gas in the region between the two sealing bulkheads as a measure of seal integrity. For canister and field fabricated units, there are no additional mating surfaces requiring seals. In the case of modular design EPAs, those EPAs with removable modules have double (inner and outer) seals with pressure integrity monitoring capability for each removable unit. For modular EPA's with non-removable moc ules, the modules are usually welded to the EPA header plate. Finally leakage along the insulation-conductor interface of cables must be considered for those EPA c esigns which are constructed with continuous, insulated conductors spanning the EPA interior.

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.sJMCT10N 903 Assch5LY - DOTN Des Figure 3 Typical Mounting of D. G. O'Brien EPA 7 3.4.1 D. G. O'Brien The D. G. O'Brien EPA is one of the three penetrations currently in production.

Figure 3 is a schematic of the O'Brien EPA shown in a typical contamment wall j mounting configuration. As may be observed from the figure, the EPA consists of onents -- the header plate and module assembly, mating module three comp connectors (i.e. mating plugs), and junction box units. It is also noted that the usu attachment of the EPA to the containment nozzle is with bolts (as opposed to welding). Containment integrity is assured by the double "o"-ring sealing configuration. The "o"-ring seahng status may be asectained via the monitaring port l

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in the header plate. Because the modules are welded to the EPA header plate, individual modules cannot be removed from the header plate assembly in the event of some sort of module related failure, such as seal integrity failure, electrical shorts or open circuits, etc. A provision for monitoring module seal integrity is provided by a header plate manifold interconnecting the module sockets to a pressure g,auge.

Insertion of modules in the header plate automatically couples the module intenor to the pressure manifold. The header plate-module assembly is evacuated throu i;h the mamfold-pressure gauge tubing and then backfilled with sulfur hexafluorice gas.

Manifold gas pressure is then used as a measure of the module sealintegrity.

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Figure 4 Schematic of Typical D, G. O'Brien Module 7 A schematic of a typical D. G. O'Brien module with mating connectors is presented in Figure 4. Several design features may be observed from the schematic. First, the (electrical) conductors in the module are terminated at both the inner and outer ends of the module. Termination is into male metal to glass headers which are welded into the module body. Thus individual conductors are insulated from the module housing and one another with an inorganic, relatively inert insulation material.

Seconc., since the electrical cables are terminated at the module (i.e., are not continuous through the module), air leakage through and around individual cables cannot contribute to loss of containment integrity across/through the EPA modules.

Thus aging should not be a factor affectmg the module electrical or sealing performance.

and outboard mating p!ugs (connectors)

Drawings are presented ofinthe inboard Figures 5 and (containment 6, respective side)ly. Since the inboard plug evolved the outboard design, we consider the outboard design first. Figure 6 is a telescoae presentation of the outboard plug in that the vanous elements " nest"inside the coupling ring in the order shown m the figure. The assembled plug is secured to the module by means of mating threads on the coupling ring and module. Although not obvious from the drawing, the insulator, contact, and washer assembly combme to form a mating female connector for the module male connector formed by the module metal to glass header. All elements of the plug assembly are rigid with the i exception of the cable grommet which is a pliable polymer base rubber.

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Figure 5 Inboard Mating Plug of D. G. O'Brien Connector 12 To assure a hermetic seal at the plug-module interface, a gasket of design and composition comparable to the cable grommet is inserted at the junction of the two components (plug and module). Since the grammet/ gasket polymer is incompressible, a torque applied to the coupling ring translates into a compressive loading of the two elements which will then flow into any voids at four (plug sleeve-cable grommet, cable grommet-insulator, insulator-interface gasket, and mterface gasket module header) interfaces and result in a hermetic seal of the plug module assembly. In earlier design EPAs, the polymer used to fabricatepommet/ interface seals had an unusually high coefficient of thermal expansion.10,n Because of this high expansion coefacient and the incompressible mechanical properties of the polymer, heating of the EPA (e.g., during accident conditions) resulted in insulation damage to the cables in the plug and the loss of seal integrity at the plug. Insulation damage and sealing loss was sufficient to cause electrica shorting between adjacent conductors. It should be noted that the exterior plug assemblies incurred no damage.

As a result of this elevated temperature behavior, the inboard (containment side) plug was redesigned in an effort to eliminate the destructive effects resulting from close confinement of the grammet/ gasket polymer. The redesigned plug is shown in Figure 5. As may be observed from the figure, a major redesign of the pluJ skirt has resulted. The closed end of the skirt plug has been been removed and rep; aced with a floating polysulfone cable guide. The cable guide rides in the modified end of the plug skirt and restrains the cable prommet. The cable guide is in turn restrained and retamed by a snap ring-wave spnng washer assembly. When the assembled plug is secured to the mating module by torquing the coupling ring, the compressive force i

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The stressed grommet then flows into any nearby voids and completes the sealing process. Durm large temperature excursions, the heated grommet expansion is accommodated compression of the wave spring washers; during cool down and grommet shrinkage, the wave spring expansion mamtains a compressive force on the cable grommet. Thus this alug redesign is intended to assure that grommet behavior will be reversible during : ari;e temperature excursions. In contrast, temperature excursions caused irreversib e grommet extrusion and sealin' loss in the o inal design EPA plugs.10,11 The redesigned module / plug assemb has been qu fied and replacements have apparently been made in all operating plants.

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A schematic of the EPA, showing the header plate and a single module,is depicted in a ical mounting configuration in Figure 7. Both the header plate and tnodule are sta ess steel. Conductors traversing the module are sealed in a ysulfone polymer at both the inboard and outboard ends of the module. The m es are secured to means of a threaded fastening device (a ".Midlock Cap") which the header allows plate by/ replacement of individual modules. Finally, the EPA may for removal l welded (as shown in Figure 8 or bolted to the containment vessel nozzle. Details of i the EPA features are expand d in Figures 8 and 9. Figure 8 shows the EPA secured to a containment nozzle. The EPA may be attached to the containment nozzle with

- bolts or by welding. If bolts are used, dual, concentric 'O"-rings assure a hermetic aperture seal at the EPA header plate-nozzle flange interface. In order to assure aperture sealing, integrity, the gas pressure in the volume defined by the two "O"-rings is monitored with a conventional (bourdon tube) pressure gage. The method for securing individuel modules to the EPA header plate is shown m Figure 9. When an individual module is secured to the header plate, it is automatically tied into a module (internal) pressure monitoring system via a manifold machined m the header plate. During the securing sequence, the module is hermetically, sealed to the header plate on either side of the module pressure monitoring mamfold. Thus all EPA interfaces through containment contain double barriers. Modules are individually secured and hermetically sealed to the EPA header plate with "Midlock Caps". The caps are analogous to a jam nut and a pair of meta wedge seals. By threading the jam nut into the EPA header plate, the pair of metal seals are forced down on the module body and out into the inside diameter of the header plate hole forming hermetic, metal to metal seals between the module and header plate.

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Figure 7 Schematic Diagram of Conax EPA and One Module 7 Module-conductor sealing is now considered. Figure 9 shows the assembly sequence.

There are no cable splices or interconnections in the module; rather all cables ~ fully insulated-make a continuous run through the module. The cable insulation for this application is polyimide (KAPTON). Each end of the cable run is cast into a d -

polysulfone insulating plug. The cable-plug combination is then assembled into a stamless steel sleeve. Tae cable-sleeve combmation is secured to the stainless sleeve at each end by means of a rolled double crimp operation. This operation compresses, and retains, the polysulfone plug-cable assembly at each end of the stainless steel sleeve. Sufficient force is applied to the the polysulfone plugs to assure hermetic seals between the polysulfone and cables and the polysulfone and stainless steel sleeve. The comp)leted assembly constitutes a module. Each mod pressure manifold when the module is assembled to the header plate.

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Figure 9 Details of Conax EPA Construction The completed EPA is evacuated and backfilled with an inert gas so that fidelity,of the hermetic seals may be monitored. Termination of the individual connectors-with pigtails, lugs, ete-is a customer option. The penetrations are certified to applicable standards which include the aging and accident test requirements of IEEE 3231974 and IEEE 317-1972.

3.4.3 Westinghouse The Westinghouse electrical penetrations are available in both canister and modular )

1 designs. The penetrations are assembled and tested at the factory. Field mounting uses either a smgle weld or bolted flange. A modular series penetration is shown in Figure 10, with detail of an individual module shown in Figure 11. The modules are held against the header plant with three mounting clamps with dual silicone o-rings forming the header plate to module seal. Connectmg a module into the header plate automatically connects it to an integral leak monitormg system. Blank modules may be ins,talled where necessary to maintain monitormg capability, and containroent ,

integrity. An epoxy sealing material is used to seal the wires mside the module.

Individual modules can be field teplaced by removing three clamps.

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Figure 12 shows a typical installation of a canister series penetration. A single field weld or bolted flange completes the installation. A canister penetrations is somewhat similar to a large single module of the modular penetrations, except that it is installed as a single unit into the containment wall.

Either type of penetration may be supplied with different types of cable, terminations, and junction boxes. The penetrations are certified to applicable standards which include the aging and accident test requirements of IEEE 323-1974 and IEEE 317-1972. I

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4.0 ,. STRESSORS AND AGING MECHANISMS 1 l

. 4.1 Normal Environments @

The possible aging stressors for the equipment under consideration are thermal, radiation, mechamcal (vibration), dust, humidity, electrical load cycling, chemical attack, and maintenance damage. Dust is not likely to be a problem except possibly for some connections. Electrical load cyc, ling will not generally contribute to aging of cable, connections, and EPA used in typica applications because of the low voltage .

levels. Increased thermal a@g resulting from cable self-heating,will be a problem for only a limited number on safety-related cables. Humidity aging is not currently considered part of the scope of qualification aging, but it may be important for some equipment.

All the components considered here can be classified as passive electrical equipment, similar in many respects to piping, connections, and piping penetrations in a mechanical system. Thus, it is expected that the normal random failure rates for L these types of equipment are ve.ry low. However, when the equipment is exposed to accident conditions following aging, the failure rate has the potential to be much higher than the normal environment failure rate. Part of the reason for this-observation is that the failure m > des are different under aging and accident conditions. Extensive research indicates the primary failure modes for most equipment under accident conflitions are moisture-related and result from the steam environments in an accident.13 Similar steam environments are not present during normal operation. Accident chemical spray environments inside containment may make some failures even more likely.

4.1.1 Cables Extensive industry testing and NRC aging research, testing has been conducted on cables. . Much of the NRC work has been directed toward determining appropriate preaging and accident methodologies for qualification testing, while industry testing is directed toward cable qualification itself. The a,ging stressors considered in most (both research and industry) testing have been hmited to thermal and radiation aging, those considered to be of most significance. Humidity, dust, operational cycling, and chemical attack are usually neglected. Humidity is specifically excluded from consideration by section 4.8 of N JREG-0588 requirements. Dust is not considered important m cable aging. Operational cycling is not signi5 cant at the voltage levels employed for most nuclear plant safety cable. Chemical attack is g,enerally not included as part of testing programs; cable is normally installed where significant chemical attack is not a problem. Mechanical aging is addressed largely by performing mandrel bend tests on aged and accident tested cables to demonstrate mechanical durability; seismic testing is generally not performed on cables.

Qualification criteria outlined in various well-known standards and regulations (see e.g. References 14-18) typically includes radiation and thermal aging, followed by an accident exposure includm' g high temperatures, pressures, steam, and chemical spr Thermal agmg is normally based on the Arrhemus methodology with g radiation based on an equal dose-equal damage" assumption.

Cable thermal aging information is frequently based on elongation at break from a tensile test. Elongation information at several temperatures is used to develop an

activation energy, which is then used to determine time and temperature requirements for simulating a given lifetime at a given temperature. Radiation damage information sometimes includes elongation also, but this is not necessary under the " equal dose-equal damage" assumption.

The components of a cable that are subject to ajing effects are primarily the insulation and jacket. Some manufacturers argue t2at the jacket is only for cable protection durmg installation and that insulation is the only

' has shown that for one particular cable type, multiconductor cables l2 ave failed in several cases where a corresponding single conductor cable did not fail; the failure

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mechanism was postulated to be a jacket interaction effect. ' Also, some cables use a composite insulation / jacket combination which may enhance any interaction effects.

Cable thermal and radiation aging mechanisms have been studied extensively (see-e.g. Reference 21 and its references) and will therefore receive limited attention here. Aging effects generally result from two different types of reactions, scission and crosslinking. Scission is a chemical process where large chain molecules are broken up; it typically results in decreased tensile strength. Crosslinking is a chemical-process where short chain molecules combine; it typically results in increased tensile strength and decreased elongation at break.

Cable functional failure is essentially limited to the loss of dielectric isolation sufficient to cause functional failure of the circuit it is used in. For the cable its (i.e. not including connections), loss of current carryirg capability is very unlikely as a result of aging effects, particularly for the low voltage (and generally low current) applications of primary mterest here. Loss of dielectric isolation may be caused by complete electrical breakdown or by reduced isolation sufficient to disrupt an electrical circuit. Changes in capacitance or other dielectric properties are rarely 4 significant in the circuits of interest.

A significant data base of aged cable properties exists within the industry, primarily from artificial aging studies. A limited amount of data from naturally aged materials much of the data is proprietary in both cases. The data is also also exists. However, insufficient to thoroug hly validate the Arrhenius technique for thermal aging anj

" equal-dose-equal-damage" assumption for radiation apng. In fact, some materials have been shown to possess mild or strong dose rate edects,22,23 indicating that the equal-dose equal-damage assumption breaks down. Fortunately, the most pooular cuuent materials in the nuclear industry for in containment safety re:ated applications tend to be among those that do not have severe dose rate effects.

Despite the inherent ruggedness of typical cable insulations, several aging related degradation mechanisms have been id entified, primarily from normal oxrational environments. A major source of this type of information is NRC Information Notices, Bulletins, and Circulars.

Circular 80-10 described two cases where improper insulation had been used on environmentally c ualified equipment. While neither case resulted in any failures, similar events cou' d result in more rapid aging of insulation resulting from usage of incorrect insulation materials.

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.Information Notice 84-68 discussed improperly rated field wires connected to l solenoid valves. The notice states that a utility was using 6 eld cable rated at 90* C (194*F) inside a solenoid valve housing that could have a continuously energized solenoid causing temperatures from 250-280*F. While this is a clear case of misapplication of cables rather than an explicit aging problem, it is actually an aging

. prob em that limits the cable temperature rating,. This notice serves as a reminder that aging can be accelerated at a local

• bot spot.

Information Notices 8649 and 86-71 were two other examples of local " hot spots" causing cable ratings to be exceeded. IE Information Notice 86-49 described insulation damage to cable used in a Class IE 4160-V bus. The accelerated insulation degradation was apyarently caused by a nearby hot (400'F) feedwater 'l line. The feedwater line insu.ation had been removed for maintenance, but was never replaced. . Information Notice 86-71 discusses burnt internal wiring that was discovered inside I.imitorque motor operator limit switch com)artments. The burnt wiring was caused by beaters inside the compartment. Tse heaters were only intended to be energized during storage to prevent moisture accumulation.

Information Notice 86-52 described insulation damage to cable used on Foxboro Model E Controllers. Cables in the control room RPS lo,gic cabinet at a nuclear plant were found embrittled after more than .10 years of se vice. Handlin; the cables had the potential to disintegrate the insulation, resulting in the possibiity of short circuits. As a result of this event, the NRC learned that the life expectancy of the cables under mild service conditions is 10 years. Further, the manufacturer recommended a yearly inspection of the cables. It should be noted that no actual failures resulted from the cable degradation. The insulation material was not mentioned in the notice.

Information Notice 87-08 discusses degraded motor leads in Limitorque motor operators. The leads were Nomex Kapton insulated and several in-service failures were reported. NRC investigation showed that the leads were never environmentally qualified. The reported failures resulted from insulation degradation that allowed leads to short together. It must be emphasized that these failures occurred during normal service.

Information Notice 87 52 discusses bi gh >otential withstand testing of silicone rubber insulated cables at a nuclear plant. T)e high potential test was to see if the cable met the 80 V/ mil post accident acceptance enterion specified by IEEE 383-1974. The testing was performed in response to concerns a>out installation damage to the cables. Although some of the cables failed this test, no conclusions regarc.ing aging are appropriate because of the severity of the dielectric tests.

Information Notice 88-89 discusses degraded Kapton electrical insulation. Kapton's vulnerability to moisture, chemical attack, and nicking (or localized damage) are indicated in the notice. From an aging standpoint, nicking is not a direct environmental aging effect, but rather occurs as a result of maintenance activities. It may contribute to enhanced degradation by other aging effects, such as chemical

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l attack.

A number of cable test programs have been performed at Sandia.19 31 The intent of these tests was to evaluate the methodology used to qualify cables. The tests were i largely concerned with evaluation of sequencing and synergistic effects under both aging and accident conditions and evaluation of dose rate effects during aging. l l

l 4.1.2 Connectors The simplicity of typical connections limits the number of age vulnerable materials they contain. Termmal blocks are often constructed of phenolic materials that are  !

very age resistant. Butt and bolt splice may have insulation that could be vulnerable to agtny, usually nylon or Kynar. Raychem heat shrink tubing and the tape discussed in section 3.2.2 are polymenc matenals that could be subject to aging.,The possible ,

failure modes of connections are either loss of dielectric isolation sufficient to disrupt 1 a circuit or loose connections. Loose connections can cause open circuits, or in some cases, electrical fires. However, the large number of terminations in a nuclear plant and the relatively few reports ofloose connections indicate that loose connections are not a significant aging, effect. Loss of dielectric isolation is most likely during accident conditions and is rarely reported during normal operation (see section 53).

Coaxial connections are typically constructed of metal with an organic insulator which might be Teflon. In a coaxial connection, the insulator is in a confined location and is for mechanical sepa'ation, which provides electrical separation. Thus, although Teflon is known to be age sensitive, its application in coaxial connections appears to render the aging effect harmless.

Most NRC information that has been disseminated regarding connections resulted from design, selection, installation, and quality assurance inadequacies, not from any aging effects.

Information Notice 80-08 describes a defect on certain States sliding link terminal blocks. The defect involved a crack in the terminal block which could result in connection problems. The defect does not appear to be directly related to aging, but aging effects such as vibration could enhance any cracking in the block. A Sandia test verified that LOCA conditions would not propagate the " crack" and lead to terminal block failure.32 .

Information Notice 82-03 discussed the requirements for maintaining cleanliness of equipment, particularly terminal blocks. Dust and chemical attack are the two mejor 8 shows no evidence possibilities for terminal block contamination. Sandia's testing ,9 that small amounts of dust might cause problems, but they do hint that chemical attack might significantly change a terminal block's performance in an accident environment, although the normal (dry) performance may not be compromised.

Information Notice 84-78 discusses underrated terminal blocks used in some limitorque motor operators. This condition resulted from improper terminal block selection and is therefore not directly related to aging. However, an underrated block may have an inherently higher failure probability under accident conditions.

This might occur, for example, because of different geometries and dimensions.

Information Notice 85-83 discusses fracture failures of terminal posts on General Electric PK 2 test blocks. The root cause of the failures was not known at the time the notice was issued. The failures may have been aging-related; no additional information is known.

Information Notice 88-27 is mostly concerned with deficient termination practices.

These included improperly stripped wires, improperly crimped connection.<, and

improperly sired connectors. None of the conditions appeared to result from aging effects, although vibration, handling, and/or chemical attack could further degrade a poor connection.

The heat shrink tubing and tapes are made from materials similar to cable materials and their degradation can be expected to be similar to cable materials to a significant extent. One advantage that these connections have over cable insulation is that they normally have significantly thicker insulation. However, their big disadvantage as compared to cable is that they must bond to existing insulation to form a moisture tight seal.

4.1.3 ElectricalPenetrations EPAs must perform two passive functions. First they must provide for the ,

i transmission of electrical signals and power to and from the reactor containment 1 structure and second they must maintam a hermetic seal between the containment interior and the exterior environment under both normal and accident conditions j Based on required EPA functions, electrical shorts and open circuits and leaks ,

around and through the EPA are the possible EPA failures.  !

I From the discussion in section 3.3, it is obvious that three general EPA elements may I be susceptible to agin,g degradation-the sealing material, the cable insulation, and, depending on mountmg method, the header plate "O"-rings. The degradation of cable aging is the same as that discussed in section 4.1.1, except that the possibility of1 interaction between cable insulation and sealing material nught become important.

The sealing materials used are typically inorganics and are thus very resistant to aging effects. The header plate "O"-nngs can be vulnerable to aging and could allow the EPA to leak if they degrade significantly. 4 Bulletin 82-04 identified deficiencies with Bunker. Ramo electrical penetrations.

While many of the deficiencies reported involved improperly selected or improperly  ;

crimped connections, one problem was identified that may be aging related to some 4 extent. The deficiency involved cracked cable insulation where tfie cables emerge from penetration modules. Contributing causes to the deficiency may have included aging, the bonding of epoxy from the penetration module to the cable insulation, a mechanical damage from movement or vibration of the cables combined with the revious factors. Aging does not appear to be the major factor in the above events p(largely a design weakness), but embrittlement of insulations could be a factor.

Ucensees were required to remedy any deficient penetrations.

Recent data 33,34 indicates that maintenance problems involving,polyimide (Kapton) l insulated wiring have been observed to be increasing. This winng is used m Conax EPAs. In aircraft electrical applications, the polyimide insulation was observed to be developing, cracks and frayed surfaces. The degradation mechanism was identified a hydrolytic chain splittmg reaction; it was determined that the degradation rate could be enhanced by elevated temperatures and high humidity conditions. Although the Conax module interior is maintained under controlled conditions, the p,olyimide  ;

extends into the containment from the EPA pigtails. Thus, high humidity agmg l (particularly at elevated temperatures) may affect polyimide's functional capability.

It should be noted that thermal agmg for EO is normally performed at high temperatures with very low humidity.

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4 4.2 Abnormal Environments Stressors As discussed in section 1.0, the stresses imposed by accident conditions, when

- combined with the effects of normal aging, are the most important consideration for

- cables, connectors, and EPAs. This observation is indicated by several NRC Information Notices describing failures which have occurred during qualification testing where the failures would never have been detected during normal operation.

The major cause of accident condition failures of most equipment is moisture related and occurs when high temperature, high pressure steam causes reduced electrical isolation in circuits. Similar. severe environments do not exist under normal operating conditions. The effects of reduced electrical isolation were studied in Reference 9 for various types of circuits and in Reference 35 for radiation monitoring circuits. Although Re,ference 9 refers spe,cifically to terminal blocks, the same type of analyses apply to any mterconnectmg device.

4.2.1 Cables The major causes of cable functional failure under accident conditions result from high temperatures and/or moisture penetration. These conditions allow leakage currents to flow to adjacent conductors or to ground, eventually causing functional failure of the circuit. Insulation resistance decreases with increasing temperature. A rule of thumb is that a factor of 2 decrease in insulation resistance results from each 10'C temperature increase.- Open circuits (not including connections) appear to be extremely rare. They would require significant corrosion of the cable conductor and would generally be detected during normal operation or periodic testing. Further, few such open circuit failures have been observed in normal service or in qualification environment degratestin[~. Twonone ation, with information notices directly related and one circular deal with harsh to aging.

Circular 79-05 discusses the potential for moisture leakage in stranded wire conductors. The phenomenon of moisture leakage through a stranded wire conductor when a differential pressure exists between the two ends of a cable is well known in equipment qualification testing. The moisture might enter a piece of equipment and cause faihire. Although any such failure is not directly attributable to ag!ng effects,it does reinforce the concept that accident failure modes may not be evident during normal service.

Information Notice S4-44 discussed inadequate qualification testing and documentation for Rockbestos cables. This notice is no longer a concern since Rockbestos performed verification testing to ensure qualification of the subject cables.

Information Notice 86-03 described environmental qualification deficiencies in the internal wiring,of IJmitorque motor operators (also suggested by Information Notice 83-72). The wiring could not be quahfled because it could not be identified and/or no qualification documentation was available for some cable that was identified.

Even though the cables did not have full . certification, they would not necessarily have failed had they been exposed to accident conditions.

Extensive accident testing has been conducted at Sandia as well as in industry. - The Sandia testing has focused on questions such as simultaneous versus sequential accident testing; single versus multiconductor q, qualification testing; and material i formulation effects. Industry tests are usually intended for actual qualification. {

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Representative reports that discuss accident testing performed at Sandia include References 19,20,30 and 31. A summary report that includes information from these references reports is Reference 13.

4.2.2 Connectors ,

The induccmh'or leakage cause currents toofother failure of connectors electrical underAaccident equipment or to ground. second cond possible failure mode is loosening of connections resulting in open circuits. In a harsh environment, temperature effects could cause a loose connection or make an already loose connection worse.

A test program was performed at Sandia to evaluate terminal blocks exposed to accident conditions. The tested blocks were unaged since (radiation and thermal) aging are not generally considered important for terminal blocks. The test profile followed was that suggested for generic qualification in IEEE 323-1974. The test was limited to 120 V and below. Many of tae terminal blocks showed leakage currents (reduced IR) sufficient to adversely affect operation of some instrumentation circuits.

Transient irs (e.g. soon after the introduction of steam or soon after changing the applied circuits. The voltage)ilure" fa mode of the terminal blocks was moisture film formation the terminal blocks allowing leakage between terminals and from terminals to ground. This is an example of where the dominant failure mode of a piece of equipment would never be seen in normal service environments.

In the testing described in Reference 8, the only failure associated with terminal block connections was attributed to excessive tension on a cable caused by extrusion of the lead wires at electrical penetrations (a testing artifact). Otherwise, tight connections remained tight. One additional observation in Reference 8 was that voltages were induced on the terminal blocks witn nothing connected to them. This was aresumably a result of galvanic reactions due to dissimilar metals on the terminal blocis, combined with the steam emironment. The terminal blocks acted as fairly strong batteries (0.5 V at about 1 mA) in some instances. The possible effects of these stray voltages on low level circuits has never been thoroughly mvestigated.

As a result of the above testing, NRC issued Information Notice 84-47. Many utilities chose to remove terminal blocks from selected circuits, based on circuit type and possible harsh emironments.

Coaxial connections, while relatively immune to aging effects (see section 4.1.2) by themselves, might be vulnerable to accident environments as a result of aging effects on coaxial cable jackets. This situation could arise, for example, if coaxial cable jacket integrity were lost during an accident and moisture were to travel along the cable shield to the connection. This would result in decreased insulation resistance and possible failure of the circuit.

Information Notice 84-57 discusses moisture intrusion in safety-related electrical equipment. While most of the events that formed a basis for the notice involved moisture intrusion into end devices, three events involved connections and one event involved cables. The cable event (LER 327/81-113) is included in the LER tabulation in Section 5, but the connection events (LERs 324/82-86,331/82-26, and did not fall within the scope of the connection LERs reviewed in Section 282/81-23)

5. Althoug h these failures occurred during normal operation, they were a resul

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n exposure to local abnormal environments. Without locally harsh environments, these degraded operation, butconnections they could cause(poor fai sealing) lures during accident conditions.

emphasis, on proper , termination procedures should help reduce the number of meidents mvolvmg moisture mtrusion mio connections.

Information Notice 86-104 discusses unqualified butt splice connections used in qualified EPAs. The connectors used nylon insulation. During testing under harsh environments, four of four samples exhibited excessive leakage currents. The affected utilities performed repairs on the splices by covering them with qualified tapes. This is another example where normal operation would not have detected the possible failure of the connectors in a harsh em'ironment.

Information Notice 86-53 discusses improper installation of Raychem heat shrinkable tubing. The generic problems discussed inclinde: a) improper diameters, b) improper overlap onto wire insuletion, c) use of the tubing)over fabric cover of improper marupulation(excessive) of the sp lice before it had cooled, and f), improper heat shrinking major concern was whether the above effects (somet2mes severe enough to expose bare wires) could lead to failures during accidents. For almost all cases where no bare wire is exposed, recent industry testmg has indicated acceptability of the splices.

The testing included artificial aging of the splices. The author is also unaware of any actual field failures (in normal operating environments) of improperly installed splices.

Information Notice 88-81 discusses qualification test failures of AMP window indent KYNAR electrical butt splices and Thomas and Betts nylon wire caps during environmental qualification. Several specimens failed during the accident portion of the test due to excessive leakage /shortmg to ground. This type of failure only occurs 1 under accident conditions and would not be detected during normal operation.

4.2.3 Electrical Penetrations All three of the penetrations discussed in section 3.3 have been qualified for IDCA conditions. These three penetrations were selected by the NRC to undergo severe i accident condition (SAC) evaluation.12 SAC environments exceed LOCA te crature and pressure conditions. Since severe accident conditions are most like to cause failures, the SAC tests will be discussed in this section. The intent of the AC testing was to evaluate the sealing integrity of typical Conax, O'Brien, and Westinghouse modular design EPA's with the umts exposed to the temperatures and pressures postulated for both BWR and PWR severe accident conditions. Although not a requirement of the test program, electrical performance of the . EPA's was l monitored throughout the severe accident exposures. Prior to the severa accident sequence, all three of the units were thermal and radiation aged to an end oflife (40 year) condition.

In testing of the D. G. O'Brien penetrations, no evidence of environmental leakage 4 either through the modules or the header Mate / nozzle flange "O"-ring seals was detected over the duration of the SAC phase. The major portion of the SAC exposure consisted of an initial quick temperature rise to 293 F, followed by a slow ,

rise over 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to a temperature of 36U F at saturation pressure (155 psia). The peak conditions were then held for 9.5 days. The unit was powered throughout the j l

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SAC phase and insulation resistance and electrical leakage measurements were 3 i

- obtained periodically over the duration of the test.' The electrical measurements results were quite similar to those obtained during the (somewhat milder) LOCA test performed at Sandia on the original design EPA (electrical shorts and moisture intrusion in the plug module interface as well as evidence of grommet / gasket l

. One module (coaxial) had irs below 100 Kn several hours into .

irreversible the test. By two flow) days into the test, all circuits had insulation resistances to groun i less than 1 Ma at 50 Vdc. With the exception of one module whose IR remained above 100 Kn throughout the test, the other module irs fell below 100 Kn at times

[

_ ranging from 2 to 6 days into the test. Five of the eight modules were passing 0.5 A currents to ground by the end of the test. Post test inspection revealed that all except -

one module were electrically faulty. It should be noted that the EPA was designe:1 -

for 65 psig/330* F peak accident conditions for periods much shorter than those used .

in the SAC exposure.

The Conax EPA that was exposed to SAC conditions also maintained seal integrity.

The EPA electrical performance was monitored thro hout the severe accident j

4 exposure. The SAC consisted of an initial rise to 640'F psia steam in 25 minutes followed by a rise to 700* F/135 psia 20 minutes later, ese final conditions were then maintained for almost nine days.- During the test, one half ampere at 28 VDC was maintained on alllow voltage conductors. Sometime during the severe accident exposure, th: inner (containment side) polysulfone seal melted as was anticipated at -

the elevated SAC temperatures. irs of the cables degraded significantly from about 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> into the test until 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> into the test when high leakage currents to ground .

required removal of the cables from the load bank. EPA thermocouple agreed quite  :

well with reference thermocouple throughout the f;AC test. Obviously, the SAC _ '

conditions greatly exceeded the EPA design criteria. i A Westinghouse EPA was also tested to SAC environments that exceeded I.DCA )

temperature and pressure conditions somewhat, but included a duration at the high temperature conditions far exceeding typical qualification conditions. The peak conditions were 75 psia steam at 400* F for 10 days. No evidence of environmental i leakage either through the modules or the header 11 ate /nor21e flange "O"-ring seals ] '

was detected over the duration of the SAC phase. "hus the unit successfully survived the primary requirements of the SAC program for EPAs. The unit was powered throughout the SAC phase and insulation resistance and electrical leakage measurements were obtained periodically over the duration of the test. The-electrical measurements were largely a function of the cable type used in the EPA.

With the exception of one conductor to conductor IR, all irs remained above 100 Kn for the first two days of the test. Some conductors maintained good irs throughout the test, while others had irs falling into the low Kn and below region.

Other information on harsh environment degradation of penetrations is discussed in NRC Information Notices. Information Notices 8120 and 81-29 described failures noted during testing of D. G. O'Brien electrical penetrations by D. G. O'Brien and Sandia National 1. laboratories. After aging, some circuits in the penetration failed under I.OCA test conditions. The grommet used in the connector expanded as a result of the aging, and 1.OCA environments. Extrusion of the grommet sealing material stripped insulation from the cables and resulted in electrical grounding during the I.OCA exposure. Retightening of the connector prior to and subsequent i to thermal aging contributed to the failure. However, this is an example of a failure

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mode that would not have been evident during normal aging but would require the

. moi sture emi ronment ssociated a with accident conditions before a failure would occur.

Information Notice 88-29 described a deficiency in qualification of Bunker Ramo .

EPAs. The deficiency was that IR readings on the EPA were not taken at fr uent enough intervals to demonstrate that the EPA would function properl for instrumentation circuits during accident conditions. Additional testing of- bese penetrations has been conducted, but the results are not publicly available.

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5.0 EVALUATION OF FAILURE DATA 5.1 Introduction This section reviews failure data that has been reported in the form of Licensee ,

Event Reports (LERs) and Nuclear Power Ex>eriences (NPE). Most of these {

repons provide an abbreviated account of the fai ure/ abnormal event. As a result,

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data on the equipment manufacturer, equipment type /model, or cause of failure may be lacking in the report. It is not unreasonable to view some isolated failure events with skepticism.

i Criteria for generating LERs are based on violations of plant Technical Specifications (TS). Thus, some single failures may simply be repaired with no LER '

fl' led. Tl e requ'rements for submitting LERs are also subject to interpretation by individua.' utilices and result in significant differences in filmg practices. Thus, few LERs on a certain topic does not necessarily indicate that the plant never has problems in the given area. Similarly, many LERs from a given plant does not necessarily indicate that the plant has a disproportionate num)er of failures compared to other plants. All LER analyses must therefore be performed and j interpreted with the above in mind.

5.2 Cables An LER search was conducted to find LERs that mig,ht be related to aging. Three different computer searches formed the basis for individual LER review. The manual LER review identified events that appeared to be related in any way to aging or the ability of aged cables to survive accident conditions. Appendix A i;ives a description of the searches and lists LERs from the period of mid-1980 to 1938 that resulted from these searches. Both inside and outside containment cables are included in the listing. Where both locations were affected, the location is listed as inside. Also, where the location was highly uncertain, the location was generally assumed to be inside.

Based on the objectives of the manual search, there are several categories of LERs which are generally not included in the Appendix A listing:

a) Events involving reactor trips caused by maintenance on or near flux monitor cables where a redundant cable was bumped or had noise spikes.

b) Events involving ribbon cables that are primarily used in benign emironmental locations, such as the control room.

c) Events involving transmission lines or other high voltage cable.

d) Events involving pinched or locally damaged cable that were clearly discovered when they happened, c) Events involving temporary jumper wires.

f) Events involving wiring that is completely internal to a piece of equipment.

However, events involving instrument lead wires that connect to field wiring is generally included.

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i Table 5 gives a breakdown on the location and category of the ERs. Because of the low number of ERs and the limited amount of information in some of them, only four cate gories were used. More than 70% of the LERs involved some type of l

funct,iona (electrical) failure, either shorting or grounding (electrical faults) or open 2 Circults.

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Table 5 Analysis of Cable ER Events (mid-1980 to 1988)

Imcation Number Percent 63 42 % ,

Inside Containment (I) 88 58 %

Outside Containment (O)

Total 151 Catecorv Electrical Fault 79 52 %

Design 38 25 %

20 13 %

Open Circuit Other 14 9%

Total 151 The category " design" includes the LER associated with improperly sized cables, incorrect assumptions about environmental exposure, installation problems, and fack of documentation to support environmental qualification. Most of the events in this category have the potential to cause aging effects and/or failures during abr.ormal environmental exposure. Many of them could have been eliminated during the other" includes such design, qualification, and installation processes.

events as cable wear, deterioration, or damage that was d The category "iscovered pr functional failure occurring but did not appear to result from exposure to higher than postulated environments.

The results shown in Table 5 yield few surarises. The number of events is very small relative to the amount of cable in a typical nuclear >! ant. This is consistent with the general feeling that cables are a highly reliable c"evice under normal operational conditions.

With due recognition of the limitations inherent in ER analyses, we will attempt to give a very rough, but hopefully conservative analysis of a failure rate indicated by the ERs.

i The number of plants currently in operation will be taken as 70. The ERs cover a period of about 3 years, but we will assume an average of 5 years coverage to account for plants which came on line during the period. We make the further assumption that 1000 circuits in each plant are involved in systems covered by Technical Specifications and that each circuit is operated an average of once per month. Both '

of these estimates are believed to be reasonably conservative. All 151 failures will be counted in the calculation, even though many of the events could be legitimately eliminated. In some sense, thit will compensate for those failures which are not l l

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l reporJed. The resulting calculation is given in Table 6, and yields a value of 4x104/ circuit demand, considerably better than typical active components.

L Table 6 Estimate of Cable Failure Rate

1. of circuits = 1000

1. plants = 70 plant age = 5 L demands / month = 1 totalfailures = 151 circuit failure rate per demand due to cables-151 failures /(1000 circuits / plant x 70 plants x 5 years / plant x 12 months / year x 1 demand / month) = 4x100 failures / circuit demand -

Table 7 gives a tabulation of the number of ER for all the plants as a function of calender year. With the small number of events,it is fairly clear that any attempt to analyze the data on a plant age basis or any attempt to look at an individual plant performance would be a statistical nightmare. Further complication arises because of changing ER reporting requirements over the years.

Table 7. Number of ERs per Calender Year Year Number of ERs 1980 22 1981 18 1982 22 1983 23 1984 10 1985 8 1986 29 1987 13 1988 6 5.3 Omnectors The same searches that were used for cables were also used as the basis for a m search for connection events. The related connection events are tabulated in )

Appendix B with reference to which of the searches contained each event.

ry of the ERs. Because of the Table 8 bves a breakdown on the location and catekormation in some off low num r of ERs and the limited amount of i five categories were used. Almost 80% of the ERs involved some type of functional (electrical) failure, either shorted, grounded, loose, or open connections.

'r Table 8 Analysis of Connection LER Events (mid 1980 to 1988)

Location Number Percent Inside Containment 68 35 %

Outside Containment 128 65 %

Total 196 Catecorv Imose Connection 62 32 %

Bad Connection 55 28 %

Design 44 22 %

Other 20 10 %

Shorted Connection 15 8%

Total 196 The category

• design" includes the LERs associated with improperly selected connectors, incorrect assumptions about environmental exposure, installation problems, and lack of documentation to support environmental qualification. Most of the events in this category have the potential to cause aging effects and/or failures during abnormal environmental exposure. Many of them could have been eliminated during the design, qualification, and installation processes. A significant number of the reported events in this category in the 1986.1987 time frame resulted from qualification deficiencies, sometimes identified during NRC EQ inspections.

The loose connection cate gory includes those events where a loose connection was clearly the cause of a bac connection. The shorted connection category includes those events where the bad connection was stated to result in a short. Where the type of bad connection was not specified, the more general term " bad connection" ect that a number of those classified as " bad connections"were was actuallyused.

looseWe andexp/or shorted connections. The category "other" consists larg moisture and corrosion related failures.

Almost all connection events involved functional failure. This is consistent with the ,

low maintenance philosophy for cables, connections, and EPAs in that little (

preventative maintenance is performed. Even with most events resulting in failures, j the number of events is very small relative to the number of connectors in a typical  !

i nuclear plant, indicating that connectors are'a relatively reliable device. It should be noted that the general utility feeling about connectors seems to be somewhat less even though the LER data does not indicate a significantly favorable than for cables,ilures higher rate of reported fa for connections. Two factors might contribute to this l j l

l xnenced First, discrepancy.

ex over connector the last few/

years heat shrink qualification have affected many connections, problems thatl but resulted relatively few LERs. Second, fewer connector failures may require LERs because of j J

reporting requirements.

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Table 9 gives a tabulation of the number of ER for all the plants as a function of calender year. . As for cables, no attempts at detailed analysis of this data will be performed because of the small number of events. The larger number of events in the 1986 and later time frame is a direct result of two factors. First, complete ER analysis was only aerformed for 19861988, with the earlier data gathered from a.

. To search that was oriy intended to identify cable-related ERs (see Appendix B)ble 9' give a feel for whether overall ERs are increasing, the second column of Ta tabulates only the ERs from search 1, which was consistent throughout the whole

. period. Second, the number of ERs falling into the " design" category was 15 in 1986 and 13 in 1987, largely because of increased awareness and emphasis on EO. After adjusting for these two factors, no indication of a year to-year increase is noted.

Table 9 Number of ERs per Calender Year Year Number of ERs Number in Search 1

'1980 13 12 1981 16 16 1982 13 12 1983 14 14 1954 6 5 ,

1985 18 12 1986 45 25 1987 61 25 1988 .10 .3 Total 196 124 5.4 Electrical EADetrations A single ER search was used as the basis for tabulating EPA LERs from 19801988.

The search produced 160 ERs and was based on all LERs that mentioned EPAs.

Of these,26 were identified as relevant to this study. Because of the small number of EPA LERs, Nuclear Power Experiences (NPE) was used as a source of additional information, from the period 1972-1980. This source gave an additional 13 events, for a total of 39 events.

When reviewing the ERs and NPEs, those EPA failures deemed to be primarily the result of personnel errors were not considered equipment failures. Failures reported  ;

here were considered to be primaril,y the result of equipment malfunction. A design defect in one model EPA was only meluded.once in the above. The defect was with connectors used to interface electrical conductors to the EPA. Misapplication of an can !

insulating r,ealing polymer in highly confining locations (in the connector body)hese result in damage to mating cables during temperature excursions. Apparently t connectors have all been replaced in operating plants.

l Table 10 divides the EPA events.into four categories. Electrical failure includes those events where in-service failures were noted. Design events involve EO, but not in service failures. The same event occurring at the same plant, but with multiple l LERs, was only counted once.

- _ = _ _ _ _ _ _ _ - _

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Table 10 indicates that pressure leakage (41%) and electrical failure (26%) caused the most events, However, compared with the number of EPAs and number of conductors per EPA, the number of events is very small. In an accident situation, the leakage events would only be important if they'om the containment. involved s EPA seals together with fission product release fr Several of the LERs, particularly those in the design category, had the potential to impact many EPAs simultaneously under accident conditions. Based on the event data in Table 10, it is evident that these are potentially the most serious of the EPA

- events. Similar to cables and connections, EPA experience demonstrates extremely high reliability during normal operation. Hence, emphasis should be placed on aging effects which have the potential to cause common mode failures under abnormal conditions.

To demonstrate the high normal reliability of EPAs based on the number of failures listed in Table 10, Table 11 gives a very crude, but hopefully conservative estimate of EPA failure rates during normal operation. Such factors as multiple modules in an EPA and multiple conductors withm a module have been neglected, as has the fact ,

that some events in Table 10 may have affected multiple EPAs.

Table 10 Analysis of EPA Events Category Number Percent Pressure 1.cakage 16 41 %

Electrical Failure 10 26 %

Design 8- 21 %

Other .5 13 %

Total 39 Table 11 Estimated Failure Rate of EPAs in Normal Service Assume about 4000 installed EPAs Assume 1 demand / month Average plant age about 10 years =90000 hours l

EPA hours =4000x90000=3.6x108 total # failures =39 EPA failurss/hr=1x10-7 i EPA failures / demand = 1x10-Ix720 hr/dem/hrand =7 1

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6.0 FAILURE MODE AND CAUSE ANALYSIS With the exception of EPA pressure leakage and EPA conductor / seal interface I failures, the failure modes are the same for cables, connections, and EPAs. "Short" or  !

open circuits are the only possible failure modes. "Short circuits"is used here to )

indicate any reduced electrical isolation (i.e. leakage cutrent) which is sufficient to cause malfunction of a given circuit. The only differences that exist among cable, connectors, and EPAs are in some of the failure causes. Open circuits are extremely rare in cables and EPAs and therefore will only be considered for connections.

6.1 Cables The information contained in the LERs discussed in section 5.2 is very limited for indicating failure modes and causes. Descriptions in the LERs are normally limited to such details as " shorted conductor," " faulty conductor," or " degraded insulation." In addition, based on the discussions in section 5.1, we feel that aging effects which could cause common mode failure during off normal conditions are the key factor in cable aging assessment. Thus, normal operational failure modes are generally not applicable for this discussion. The only significant data for cables subjected to off normal conditions comes from EQ testing.

Data from normal operational conditions is important when assessing how results of mechanisms that are not considered in EO EQ tests might be affected testing. For exam)1e, cables that areby " aging" damaged during installation or mainten but not discoverec immediately, will have a higher likelihood of failure under off normal conditions than will undamaged cable (although the amount ofincrease is very uncertain). Detection of and off normal environmental performance oflocally damaged cables is the subject of a current EPRI sponsored program at Sandia.36 The LER data gives an indication that the number of damageci cables that were not discovered immediately is fairly low. However,- the damaged cables that are discovered at a later time are those that are sufficiently damaged that they are detected during normal operation. Also, the damaged cables had to result in violation of a fechnical Specification to be reported. Cables which are not sufficiently damaged for detection during normal operation may never be discovered.

Both industry and research EQ testing 3rovide some insight into the failure modes of when cables fail in industry tests, cables during accident conditions. Un?ortunately,if the results are not generally reported in any detail, they are reported at all. Wh r rted is often considered proprietary. Thus research tests form the major source ,

o ublicly available data.

In two Sandia tests, the same aged multiconductor cable failed as a result of an apparent insulation / jacket interaction effect that was enhanced by dimensional changes which were caused by moisture absorption; single conductors removed from the multiconductor cable did not fail nor did unaged multiconductor cables. No other gross failures have been noted during past Sandia testing. Several additional failures have been noted in current Sandia tests associated with the NPAR program; they will be discussed in future reports.

The following are some failure modes and causes that might occur during accident conditions:

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• a) Probably the most important failure mode is electrical faPures which are preceded by mechanical degradation, such as the insulation / jacket mteraction effect discussed above or actual cracking of a cable that has been aged. He mechanical damage allows moisture to create electrical paths to adjacent conductors or ground, resulting in electrical failure. This failure mode might,go undetected during type testing if the aging simulation performed is not adequate or if the type test sample selection is not adequate (such as if single conductors are used to simulate multiconductor cables when an insulation-jacket interaction effect is important).

b) A second possible cause of failure under accident conditions is reduced insulation resistance due to cable material that is not particularly effective at resisting the high temperature and pressure effects of the accident steam. In this case, the IR might decrease below acceptable levels during the accident, but then recover as the accident conditions are reduced. This failure mode would be of concern primarily for instrument cables that require high insulation resistances. In contrast to a) above, this failure mode is more likely to a ) ply to unaged cable as well as a[ed cable. His failure mode would like y be detected if an adequate IEiE383 type test was , performed on the cable product. However, selection of type test specimen (such as single vs. multiconductor) might be important here also.

is reduced IR due to moisture c) A failure mode closely related to b)he bulk IR is reduced because of absorption and swelling. In this case, t moirture presence within the insulation. This failure mode may act in combination with b) to produce a failure or it may be a partial cause for failures discussed in a). This failure mode would also likely be detected if an adequate IEEE383 type test was performed on the cable product.

6.2 Connections Terminal blocks were studied in an extensive experimental programs 8,9 at Sandia.

The objective of that program was to determine the failure and degradation modes of terminal blocks. The basic hypothesis of the terminal block tests was that any failure modes would be related to electrical leakage paths through moisture films on the terminal Hock surfaces. Significant reduction in irs of the terminal blocks was observed when steam was present, resulting in the conclusion that " surface moisture films are the most probable explanation for the observed degradation of terminal block performance. This type of performance degradation is only associated with accident performance and would not be detected dunng normal operation.

Because of the materials used in terminal block construction, it is unlikely that aging would have a significant impact on accident performance. The one possible exception to this statement is that corrosion and/or dirt accumulation on tlie blocks might affect their performance. It should be noted that corrosion and dirt accumulation are largely ignored under current qualification requirements; the assumption is that normal maintenance would identify and correct any such degradation mechanisms.

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Aside from electricalleakage, other possible failure modes under accident conditions ,

are open circuits or gross electrical breakdown (more severe than just leakage currents). Open circuits are most likely to be associated with the connector attached i to the terminal block. Aging effects (e.g. vibration and thermal expansion and contraction) can cause or enhance these loose connections. However, open circuit failures are not likely to be enhanced by an accident. In fact, the enhanced surface conductivity resulting fro.n an accident might reduce the effects of a loose connection. It should be noted that an open circuit failure was observed in the Sandia tests, but its primary cause was cable extrusion through test chamber penetrations which put a sigmficant tensile stress on the cable. Based on the test results, gross electrical breakdown during an accident doesn't seem likely at voltages typical of most nuclear power plant usage. Two possible exceptions to this statement apply to blocks which may be contaminated with dirt and/cr corrosion and to blocks which are used at voltages above 120 V. For a more detailed discussion of failure modes see section 7.0 of Reference 9.

i Many of the same comments that apply to terminal blocks also apply to other splices.  !

of splice connections also used for Open circuitto failures connections (loose is terminal blocks) connections)likely most on the crimped p(ortion of the connection rather than at any screwed or bolted connection. Inadequate crimping is the most likely root cause for this type of failure.

Electrical !cakage or shorting is the more likely failure cause under accident conditions. Most safety-reinted butt splices inside containment are protected by tape or heat shrink tubing. Heat shrink tubing and tape materials are similar to cable materials, but they are normally significantly thicker than cable insulation. Electrical leakage through, tape or heat shrink can be caused by the all the same mechanisms as for cables, but m addition, correct installation and ' adhesion of the tape or splice is important. A number of Information Notices related to splices were discussed in Sections 4.1.2 and 4.2.2. .

63 Electrical Penetrations Because EPAs basically consist of standard field cables assembled into a hermetically sealed system, electrical failure modes of EPAs include all possible failure modes of cables as discussed in Section 6.1 above. In addition, the sealing system can introduce new failure modes not present in other field cable. An example of a sealing interaction effect is discussed in an Information Notice (see Section 4.23).

Another possible sealing interaction effect could result if cables swelled or had other dimensional changes near the sealing interface, resulting in damaged insulation.

Aging effects might change the way cabler. Interact with the sealing mechanism.

Leakage through both seals of EPAs is rare. Most LERs report leakage through only one seal. In severe accident testing at Sandia, none of the three penetrations tested showed an,y signs of significant leakage. Thus, leakage failure modes appear to be much less unportant.

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~ 7.0' TESTING AND MAINTENANCE Cables, connections, and EPAs generally receive minimal testing and maintenance attention. In large part, this is because of high normal reliability of the equipment.

Lack of effective testing methods also limits test activities. Most maintenance which 1

is performed is corrective maintenance rather than preventative maintenance. For example, many utilities have inspected and/or reworked many connections as a result of NRC and industry concerns that installations had not been performed in accordance with quah'tication requirements. Some plants do have requirements for--

physical inspection and cleanliness of connections and wiring near an end device when maintenance is performed on the end device. Monitoring of pressure in EPAs to detect leakage is required in every plant.

Where routine electrical testing is performed, the most common test is insulation resistance. Acce which affect IR. ptance criteria are difficult to determine because of the of terminations. Usually the test is used as pass / fail and actual values may or may not be recorded.

4

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8.0 CONDITION MONITORING Because cables, connectors, and EPAs are relatively low maintenance, high reliability components, few utilities perform extensive routme measurements on them. The measurements that are performed are normally intended for go/no-go acceptance tests, rather than for condition monitoring (CM). Thus, detailed test results may not 4 be recorded. Probably the most popular measurement that has been used by utilities is insulation resistance. Other measurements that some utilities have used include continuity tests, polarization index, big potential testing, capacitance, partial 3 discharge, and time domain reflectometry. Ilumber of these measurements may be made automatically using the ECAD system. /

8.1 Sandia NPAR Phase IIProgram Phase II of the NPAR program for cables is already underway at Sandia. A number of different CM techniques are being used in the Phase H test program. They include 1 both nondestructive, in situ tests and laboratory tests on small specimens that were periodically removed from the aging portion of test program. The planned CM techniques for the Phase !i program are as follows: {

a. Dielectric withstand voltage. Dielectric withstand (breakdown) voltage of cable samples will be performed using a voltage ramp rate of 500 V/s on small samples removed during aging. This dielectric withstand test is one measure of the ultimr.te electncal capability of the insulation.

b. Ultimate tensile strength and elongation. These measurements, in particular elongation, have historically been used by the cable industry'to assess the thermal ag,in behavior of low-voltage cable materials. They have also been extensiv used to characterize the susceptibility of cable materials to dose rate an synergistic aging effects. Elongation at break is used since it typically decreases with increased aging. In contrast, tensile strength may first increase, then decrease with age, and therefore is used less often to characterize aging behavior.

Our measurements use test specimens about 6 inches long that are removed during aging. We prepare the tensile specimens by disassembling the cables prior to the start of tae aging exposure.

c. Modulus pro 5 ling. The clastic modulus is a measure of the slope of the stress vs. strain curve in the initial linear portion of the curve. Modulus profiling considers the variation of the modulus over the cross section of a specimen.24 Changes in insulation modulus have been shown to correlate with thermal aging degradation. However, for ethylene propylene rubber (EPR) materials, modulus has not always correlated well with radiation degradation. In certain circumstances, modulus profiling, of cable specimens gives an indication of aging uniformity and hence is xing used in our test rogram to help assess whether dose rate effects have been eliminated test parameters.

d. Hardness testing. Hardness is a material's resistance to local penetration.

It is measured with any of a variety of hardness testers. While the modulus profiling technique yields much more quantitative information, the J

h wi ^

N

. measurement technique that has demonstrated some correlation to-t polymer degradation.E e

e. Bulk' density. Density measurements have derggnstrated that insulation

. ~ density tends to increase with aging by oxidation.c Thus, as for modulus, e it may be subject to gradients resultmg from oxygen diffusion effects. In the Phase Il program, bulk density is being measured for selected samples-and other techmques, such as modulus profiling, diffusion.are being us indication of the gradients resulting from oxygen

f. iInsulation resistance measurements as a function'of voltage and time.

4 Information that can be deduced from the insulation resistance measurements includes insulation resistance at a specific time (one minute.

is a time that is typically employed by industry), polarization mdices, and step voltage behavior (i.e., insulation resistance as a function of voltage).

For our tests, insulation resistance measurements are performed from each conductor to all other conductors. Measurements are taken at 50, 100, and 250 V. I2akage current (or insulation resistance) data is taken at discrete time points from 2 seconds to 1 minute for 50 and 100 V measurements and from 2 seconds to 5 minutes for 250 V measurements.

Insulation resistance gives a measure of the resistive component of the dielectric impedance.

g. Transfer function as a function of frequency. Parameters that can be calculated as a function of frequency from the transfer function are real and imaginary components of the complex transfer function, capacitance and dissipation factor, real and imaginary (loss) components of complex capacitance, power factor, loss angle, etc. The transfer function gives an indication of the variation of dielectric impedance (principally due to the bulk cable capacitance and conductance)es a function of frequency. The component of the transfer function gives an indication of the imaginary' dielectric charge / voltage characteristics at the given frequency, and t phase angle between the real and imaginary components gives an mdication of the dielectric losses as a function of frequency. The tang)ent of the phase angle 6 is commonly referred to as theency. dissipation F) ( ion factor and is often measured only at a single discrete Dissipat factor also gives an indication of the power factor since the two are related as PF=DF/(1+DF2). If 6 is a small angle, e PF-DF.

i. Two additional CM techniques planned for the Phase II test program are Indentation testmg will use indentation testing and step voltage a Franklin Research Center test apparatus response)8 developed under Electric Power Research Institute (EPRI) funding. Step voltage response (Time or TDS) of small samples to measure transfer

, Domain Spectroscopy,hnique function 39,40 is a tec advanced at the National Institute of Standards and Technology (NIST). It has particular applicability at very low frequencies. Measurements will be performed through a cooperative program with NIST.

Some of the above techniques are also applicable to connections and EPAs.

1.

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,4 8.2 Other Condition Monitorine Activities

Several utilities have ongoing cable condition monitoring activities. 'A program at Oconee41 has been ongomg since the early 1970s when Oconee began commercial but five of them operation in 1973. Six offerent cable types are included in the study,d in the industry have an outer metallic sheath which is not typical of most cable use After the first 5 years of operation, the " rate at which the test samples aged in thg.

reactor environn.ent was as expected."41 A similar program is underway at Perry,44 which began commercial operation in 1987. Cables more re preventative of overall industry usage are included in this program, but because of 12e recent beginning of; commercial operation, results from this program will not be available for some time.

' The University of Connecticut is performing a study to compare artificial and natural and aging of various components, including cables,- heat shrink tubing,heast feedthrou ghs.43 The stu is funded by EPRI, Detroit Edison, and Nort Utilities.1 able 12 is alist o nts participating in the study and a list of cables, heat shrink, and feedthroughs incl ded in the study. Not all specimens listed in Table 12 are included in all plants. Specimens were placed in the plants in 1985. In addition to the naturally aged, additional identical test specimens are being naturally, aged to -

allow for companson between the two groups. The University of Connect cut also has a small program, funded by Northeast Utilities, involvin The program began m 1980 and developed into the larg ointly funded program desenbed above.

c

' Table 12 Plants and Components 1ncluded in University of Connecticut Study Elants Components D. C. Cook 1 BIW EPR/CSPEInstrument Cable 12Salle 2 Kerite EPR/CSPE Power Cable Maine Yankee Okonite EPR/CSPE/CSPE Power / Control Cable Millstone 2 Rockbestos XLPE/ Neoprene Control Cable Peach Bottom 3 Kerite FR/FR Power Cable Point Beach 2 Samuel Moore FR 90' C Instrument Cable Trojan Rockbestos Coaxial Instrum:nt Cable WNP-2 Brand Rex XLPE/CSPE Power / Control Cable General Cable EPR/ Neoprene Instrument Cable Samuel Moore EPR/CSPE Control Cable Raychem CoaxialInstrument Cable Raychem XLPE Controllable Anaconda FR EPR/Polychem Instrument Cable ,

e Thermocouple Cable BIW ConaxTyp/8" 3 and 1/2" Feedthroughs Raychem WCSF 300 (2818) N3672-2-2 Shrink Tubing

• Abbreviations are defined as for Table 1 San Onofre employs a cable monitoring program based on the ECAD system.44 Although none of the measurements performed by the ECAD system has yet been shown to have a definitive trend with cable condition, the ECAD system is apparently

'r .

a valuable diagnostic tool. In addition, future research may establish trends for one or more of the parameters measured by the ECAD system.

A number of papers presented at the 1988 EPRI Cable Condition Monitoring Workshop dealt with various possibilities for cable condition monitoring. None of the techniques has yet been shown to have the capability of predicting cable performance in abnormal environments. A study >erformed by Ontario Hydro 45 tentatively concludes that "de or ac hipot tests may Se the easiest means of gaining some confidence that the insulation can survive many more years of o3eration.

However, additional research is suggested to establish validity of this conclusion and to determine appropriate test voltages. A study at the Umversity of Tennessee 46 examined solvent extraction, differential scannmg calorimetry, Fourier Transform and small angle X-ray scatten'ng for monitoring of thermal Infrared Spectroscopy,The degradation of cables. one application of these methods given in the paper used a t acrmally aged, thickwalled XLPE cable.

Several additional papers 47-51 Eenerally describe possible cable condition monitoring techniques, either for local de gradation, global degradation, or both. Of particular interest is Reference 47 whic 1 indicates that one cable manufacturer's ex>erience is that about 90% of cable failures resulted from physical damage to ca31es before, during, or after installation.

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8.0 CONCLUSION

S

' The conclusions from this study are as follows:

~

a) Cables, connections, and EPAs are highly reliable devices under normal plant operations, with no evidence' of significant failure increases with aging. Consequently, they receive little or no preventative maintenance.

0

,' b)- The most significant ;ging affects are those that have the potential to cause common mode fwlures during accident conditions.

c) Many of the accident failure modes of cables, connections, and EPAs normal o would high te not be cratures detected and humi during,dities.

)e mostT;M: ration important because failure mode is-of the abs shorting or reduced electrical isolation). Several different causes may .

resultin failure mode. ..

.d) Plant operational experience is useful to the extent that it may indicate some possible accelerated degradation mechanisms for cables, connections, and EPAs that could lead to common mode failure under off-normal environmental conditions. However, current LER data provides a very limited database for this purpose.

e) A significant number of manufacturers have produced cables, connections, and EPAs, resulting in many different materials and construction methods.

Consequently, generic assessments of aging effects and vulnerabilities

. become much more difficult.

b

_ = _ _ _ _ - _ _ _ __ _

u 3,

9.0. REFERENCES

1) " Nuclear Plant Aging Research (NPAR) Program Plan." NUREG-1144, Rev.1, U.S. Nuclear Regulatory Cormmssion, September,1987.

2) M.'J. Jacobus, G. L Zigler, and L D. Bustard, " Cable Condition Monitoring Research Activities at Sandia National Laboratories," SAND 88-0293C, k spears in Proceeding:SR, Workshop on Power Plant Cable Condition Monitoring, E*RI EL/NP/CS-59:.4-July,1988.

3)- M.' J. Jacobus,

• Condition Monitoring and Aging Assessment of Class 1E Cables," SAND 88-2151A, Appears in Sineenth Water Reactor Safety Information Meeting,989.NUREG/CP-0097, March,1 Vol. 3, U.S. Nuclear Regulatory C

4) S. Ahmed, S. P. Carfagno, and G. J. Toman, " Inspection, Surveillance, and Monitoring of Electrical Equipment Inside Contamment of Nuclear Power Plants - With Applications to Electrical Cables," NUREG/CR-4257, ORNL/Sub/83-28915/2, Oak Ridge Nationallaboratory, August,1985.

5) A. Sugarman, B. Kumar, and R. Sorensen, " Condition Monitoring of Nuclear Plant Electrical Equipment," EPRI NP-3357, Research Project 1707-9, NUTECH Engineers, San Jose, California, February 1984.

6)

A. R. Ducharme and L. D. Bustard, " Characterization of In-Containment Cables for Nuclear Plant Life Extension," Presented at the ASME/JSME Pressure Vessel and Piping Conference, Honolulu, HI, July,1989.

7) W. Sebrell, "The Potential for Leak Paths Through Electrical Penetration Assemblies Under Severe Accident Conditions," NUREG/CR-3234, SAND 83-0538, Sandia National Laboratories, July,1983.

8) C. M. Craft, " Screening Tests of Terminal Block Performance in a Simulated LOCA Environment, NUREG/CR-3418, SAND 83-1617, Sandia National Laboratories, August,1984.

9)

C. M. Craft, " Assessment of Terminal Blocks the Nuclear Power Industry,"

NUREG/CR-3691, SAND 83-0422, Sandia National laboratories, September, 1984.

l- uipment Qualification 10)

W. H. Buckalew, F. V. Thome, and D. T. Furgal, Research Tests of the Duke Power / D. G. O'Brien e K Instrumentation Penetration Assemblies," RS 4445/81/03, Sandia tional Laboratories,

' March,1982.

11)

W. H. Buckalew and F. J. Wyant, "The Effect of Environmental Stress on Sylgard 170 Silicone Elastomer," NUREG/CR-4147, SAND 85-0209, Sandia NationalI2boratories, May,1985.

D. B. Clauss, " Severe Accident Testing of Electrical Penetration Assemblies,"

12)

NUREG/CR-5334, SAND 89-0327, Sandia National Laboratories, August, 1989.

49-

0,:

,7 . . H i

13)' ' L L Bonzon, F. J. Wyant, L D. Bustard,'and K. T. Gillen, " Status Report on Ec uipment Qualification Issues: . Research and Resolution," NUREG/CR-' j 43bl, SAND 85 1309, Sandia National bboratories, November,1986. 1

14) "Environn ental Qualification of Electric' uipment Important to Safety for Nuclear Power Plants," Code of Federal R ons, Title 10, Part 50, Section 50.49, January,1983.

.I 15)' " Guidelines for Evaluating Environmental Qualification of Class 1E Electrical ,  !

J Equipment in Operating Reactors," Supplement to IE Bulletin 79-01B, U.S.

Nuclear Regulatory Commission, January,1980. .

16) " Interim Staff Position on Environmental Qualification of Safety-Related

- Electrical Equipment," NUREG-0588, Rev.1,- U.S. Nuclear Regulatory ' i Comminion, July,1981.

17) "lEEE Standard for Qualifying Class IE Eculpment for Nuclear Power Generating Stations," IEEB Std 3231974, he Institute of Electrical and Electronic Engineers,1974.

18) "IEEE Standard for Type Test of Class IE Electric Cables, Field Splice's, and -

Connections for Nuclear Power Generating Stations," IEEE Std 383-1974, The Institute of Electrical and Electronic Engineers,1974.

19) L D. Bustard,"The Effect of LOCA Simulation Procedures on Ethylene Propylene Rubber's Mechanical and Electrical Properties," NUREG/CR-3538,

- SAND 83-1258, Sandia National 1. laboratories, Octo ar,1983.

20) P. R. Bennett, S. D. StClair, and T. W. Gilmore, "Superheated-Steam Test of Ethylene Propylene Rubber Cables Using a Simultaneous Aging and Accident Environment," N'UREG/CR-4536, SAND 86-0450, Sandia National bboratories, June,1986.

21) K. T. Gillen and R. L Cloug,h, " Time-Temperature-Dose Rate Superposition:

A Methodology for Predictmg Cable Degradation Under Ambient Nuclear Power Plant Aging Conditions," SAND 88-0754, UC-78, Sandia National bboratories, August,1988.

22) R. L Clough, K. T. Gillen, and C. A. Quintana, " Heterogeneous Oxidative Degradation in Irradiated Polymers," NUREG/CR-3643, SAND 83-2493, Sandia National bboratories, April,1984.

23)

K. T. Gillen and R. L Clough, " General Extrawlation Model for an Important Chemical Dose-Rate Effect," NUREG/CR-4008, SAND 84-1948, Sandia l National bboratories, December,1984.

24) K. T. Gillen, R. L. Clough, and C. A. Quintana, " Modulus Profiling of Polymers," Polymer Degradation and Stability, Vol.17, p.31, (1987).

25) K. T. Gillen, R. L Clough, and N. J. Dhooge, " Density Profiling of Polymers,"

Polymer, Vol. 27, p.225, L986.

t .

26)

K. T. Gillen and R. L Clough," Applications of Density Profiling to Equipment Qualification Issues," NUREG/CR-4358, SAND 85-1557, Sandia National Laboratories, September,1985.

27) O. Stuetzer, " Status Report: Correlation' of Electrical Cable Failure With Mechanical Degradation, NUREG/CR-3263, SAND 83-2622, Sandia National Laboratories, April,1984.

Simulation

28) LProcedures D. Bustard, et al., "ne Effect of Thermal and Irradiation N} ink 651, Sandia on Polymer Properties," NUREG/CR-3629, SAND 3-Nationallaboratories, April,1984.

29) L. D. Bustard, "Etbylene Propylene Cable Degradation During LOCA Research Tests: Tenstle Properties at the Completion of Accelerated Aging,"

NUREG/CR 2553, SAND 82 0346, Sandia National Laboratories, May,1982.

l-

30) L D. Bustard,"The Effect of LOCA Simulation Procedures on Cross Linked Polyolefin Cable's Performance," NUREG/CR-3588, SAND 83 2406, Sandia l National Laboratories, April,1984.

31) L D. Bustard, et al.,"The Effect of Alternative Agint and Accident Simulations on Polymer Properties," NUREG/CR-4091, SAN 384-2291, Sandia National Laboratories, May,1985.

32) L L Bonzon, et al., "LOCA Simulation Thermal Shock Test of Sliding-Link Terminal Blocks," NUREG/CR-1952, SAND 81-0151, Sandia National Laboratories, May,1981.

33) F. J. Campbell, " Temperature Dependence of Hydrolysis of Polyimide Wire Insulation," IEEE Transactions on Electrical Insulation, Vol. EI-20, No.1, February,1985.

34) C. J. Wolf, D. L Fanter, and R. S. Soloman, " Environmental Degradation of Aromatic Poly ~ imide-Insulated Electrical Wire," IEEE Transactions on Electrical Insulation, Vol. El-19, No. 4, August,1984.

35) E. H. Richards, M. J. Jacobus, P. M. Drozda, and J. A. Lewin, " Equipment Qualification Research Test of a High-Range Radiation Monitor,"

NUREG/CR-4728, SAND 86-1938, Sandia National Laboratories, February, 1988.

l 36) G. Sliter, " Overview of EPRI Activities in Nuclear Plant and Cable Life Extension," Appears in Proceedings: Workshop on Power Plant Cable Condition Monitoring EPRI EL/NP/CS-5914-SR, July,1988.

37) R. D. Meininger, " Electronic Characterization and Diagnosis," Appears in Proceedings: Workshop on Power Plant Cable Condition Monitonng, EPRI EL/NP/CS-5914-SR, July,1988.

38) G. J. Toman and G. Sliter, " Development of a Nondestructive Mechanical Condition Evaluation Test for Cable Insulation," Presented at the International ANS/ ENS Topical Meeting on the Operability of Nuclear Power Systems in Normal and Adverse Environments, Albuquerque, New Mexico, September 29-October 3,1986.

~,. .

i- 39) F. I. Mopsik,'The Transformation of Time Domain Relaxation Data Into the Frequency).

957 (1985 Domain," IEEE Transactions on ElectricalInsula

40) F. I. Mopsik, " Precision Time Domain Dielectric Spectrometer," Rev. Sci.

Instnan., Vol. 55, p.79, (1984).

41) T.J. Al Hussaini," Cable Condition Monitoring in a Pressurized Water Reactor Environment," Appears in Proceedings: Works. hop on Power Plant Cable Condition Monitoring EPRI EL/NP/CS-5914 SR, July,1988.

42)

S. Kasture and S. Litchfield, " Cable Condition Monitoring Program at Perry Nuclear Power Plant," Appears in Proceedings: Workshop on Power Plant Cable Condition Monitoring EPRI EL/NP/CS-5914-SR, July,1988.

43)

M. T. Shaw, " Natural Versus Artificial Aging of Materials in Nuclear Plant Equipment," EPRI NP-4997, Electric Power Research Institute, Palo Alto, CA, December,1986.

44) R. J. St. Onge, " Cable and Electrical Apparatus Monitoring Program at San Onofre Generating Station (SONGS) Unit 1," Appears in Proceedings:

Workshop on Power Plant Cable Condition Monitoring, EPRI EL/NP/CS-5914-SR, July,1988.

45) G. C. Stone, D. M. Sawyer, and B. K Gupta, " Electrical Testing of Generator Station Cables," Appears in Proceedings: Workshop on Power Plant Cable Condition Monitoring EPRI EL/NP/CS-5914-SR, July,1988.

46) P. J. Phillips, " Characterization of Cable Aging," Appears in Proceedings:

Workshop on Power Plant Cable Condition bionitoring, EPRI EL/NP/CS-5914 SR, July,1988.

47) T. H. ling, " Cable Life and Condition Monitoring - A Cable Manufacturer's View," Appears in Proceedings: Worksh on Power Plant Cable Condition Monitoring EPRI EL/NP/CS-5914-SR, Jul ,1988.

48) P. H. Reynolds, " Conventional Cable Testing Methods: Strengths, Weaknesses, and Possibilities," Appears in Proceedings: Workshop on Power Plant Cable Condition Monitoring EPRI EL/NP/CS 5914 SR, July,1988.

49) J. B. Gardner and T. A. Shook, " Status and Prospective Application of Methodologies from an EPRI Sponsored indenter Test Pro ect, Appears in  ;

Proceedings: Workshop on Power Plant Cable Condition konitoring, EPRI EL/NP/CS-5914-SR, July,1988.

50)

W. L. Weeks and J. P. Steiner, " Electrical Monitoring for Cable Changes,"

Appears in Proceedings: Workshop on Power Plant Cable Condition Monitoring, E?RI EL/NP/CS-5914-SR, July,1988.

51)

F. D. Martzloff, "A Review of Candidate Methods for Detecting Incipient Defects Due to Aging ofInstalled Cables in Nuclear Power Plants," Appears in Proceedings: Workshop on Power Plant Cable Condition Monitanng, EPR1 EL/NP/CS-5914-SR, July,1988.

, 1 i

yi 4 APPENDIX A Cable Events -

l The following LERs resulted from three computer searches (indicated by reference q under I/O): q 1

1)' Select all ERs between 1980 and 1988 involving problems with cables

- (1458 ERs). ]

2

2) From all ERs between 1980 and 1988 involving problems with cables, connectors, insulation, and terminal blocks, select those that involve an equipment qualification problem OR fabrication activity (172 MRs).

3) From all ERs between 1980 and 1983 involving problems with' cables, connectors, insulation, and terminal blocks, select those with event dates between 1986-1988, but exclude any ERs in Group 2 (456 ERs).

In the LERs listed below, every cable event was included in search 1 except for two. Almost all events between 1986 and 1988 were included in either search 2 or search 3, indicating that search 1 essentially provided the same information as searches 2 and 3.

LER #* 1/_Q" Description 250 80-17 I 1 Grounded cable on power range nuclear instrument 259 80-35 I 1 Shorted wires in level switch caused low oil level alarm for recirculation pump 260 80-50 I 1 Open circuit m IRM due to bad cable 261 80-14 1 12 No EQ documentation for PVC pigtail wire used on EPAs 265 80-33 O 1 Grounded wire in generator to bus circuit breaker auxiliary contacts 269 80-2 O - 1 HPSW p 272 80-14 O 1 Ground m, ump motor cable shorted from water in condu transformer to deenergize 272 80 15 O 1 Ground in field wiring to RHR sump pump alarm 281 80-4 I 1 Pressure transmitter moperable because of a cable problem 293 80 66 O 1 Broken wire in governor control assembly to Diesel fire pump 296 80 1 O 1 Feeder cable faulted to bus tie board 296 80-11 0 1 Wire to RWCU valve failed due to work hardening near connection 296 80-43 O 1 Water from heat exchanger removal shorted signal lead to radiation monitor 296/80-56 I 1 Open wire in cable caused Diesel voltage available relay to be deenergized, apparently due to cable damage during modi 5 cation

• The first 3 numbers of the ER number are the plant docket number.

"I=Inside Containment O=Outside Containment Numbers refer to the searches where the ER was found

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - _ - _ _ _ _ _ _ _ _ _ _ _ _ _ - -- - - - - - - - - - - - - - _ _ -- - u

m.

- l j

316 80-25 I 1 Insulation failure on cable to vent fan caused fan to trip "

317 80-67 I 1 Broken tem perature element lead wire in reactor protective system 324 80 47 I 2 SOV pigtails with fiberglass tape overwrap found brittle and easily i damaged l 327 80-18 I 12 Exposed cable not qualified for radiation dose 335 8013 O 12 DG exciterlead cables hot and burnt undersized 339 80-3 0 1 Faulty lead on DG monitoring instrumentation 366/80-52 O 12 Heater cable for SGTS undersized 366/80 66 O 1 Ground in cable to HPCI isolation circuit caused isolation during RCIC testing l 254/81-7 I 1 Shorted conductors in recirculation pump discharge valves 255/81-45 0 1 Fault in power su ply cable to fire protection annunciator caused by broken wire stran from apparent pmching ]

259 81-49 I 1 Damage to SRMs and IRMs cables during maintenance f 261 81-8 O 1 Open control cable to CCW valve 269 81-20 1 1 Cable to hydrogen purge unit frayed and embrittled by beat and a vibration j 277/81-40 1 1 Inadequate assurance that radiation monitor cable would perform at i high temperature 280/81-62 O 1 Broken wire to radiation monitor detector probe 302/81-70 I 1 Grounded cable to neutron flux monitor caused loss of audible counts m containment l 302/81-77 O I Diesel control circuit grounded due to electrical conduit separating i and rubbing cable insulation i 315/81-6 O 1 Broken conduit bushing allowed conduit to cut and ground charging pump inlet isolation valve cable 315/81-31 I 1 Containment interlock inoperable-broken wire 324/81 137 O 1 Electrical short to ground of RCIC MOV trip solenoid control power lead 1 327/81 113 O 1 Short in ice condenser system val've cable junction box saturated with i liquid from the glycol expansion tank 334/81-94 O 1 Electrical short m wiring harness to hydrogen analyzer pinched by cabinet and found smoking 338/81-61 1 1 Damaged T/C cable to hydrogen recombiner heater 4 364/81-42 0 1 Broken wire in instrumentation drawer for containment particulate radiation monitor 369/81-42 O 1 Broken wire to seismic monitoring remote starter 1 369/81-161 1 12 Cable to HRRM not qualified for high temp. I 255/82-40 0 1 Damaged wires in remote flow switch caused short in fire system alarm aanel 271 82-12 O 1 Frayed wire found in breaker for SW pum) 272 82-15 O 1 Wire to undervoltage relay shorted to feed er cubicle door 277 82-41 0 1 Frayed wire caused short to RWCU high temp. isolation switch-caused false initiation signal 280/82-13 I 1 Corrosion in CRD cable due to from nick in cable 281/82-08 O 1 Feeder cable to transformer failed apparently due to brackish water 296/82-27 I 1 Naged lead to SOV caused failure to operate 302/82-17 O 1 Water in junction box and cable-fluctuating readings on reactor building pressure indicator 324/82-15 1 1 Tear in cable caused ground in IRM signal cable 325/82-113 1 1 Insulation to SRM was cut, resulting in short i

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327/82-50 O 1 Broken lead to annunciator born caused loss of control power to DG 327/82-76 O 1 Power wire to ice bed temperature monitor broken due to pinching when drawer was pulled out -

328/82-83 1 1 Condulet cover pinched and grounded wire to isolation valve for steam generator blowdown sample line 332 82-4 O - 1 Power to RHR pump lost due to fault in 4 kV cable 336 82-13 O 2 Undersized ground wire to MOV overheated 361 82-148 O 1 Grounded wire in salt water cooling system control circuit 364 82-29 O I Ground fault on power cable to nyer water pump 369 82-10 O 1 Cable to digital rod position indicators susceptible to conductor damage under flexure due to their own weight 369/82-48 1 1 Wire pinched by deformed conduit to PORV limit switch 373/82-l' O 1 Brok,en speed cable to Diesel fire pump prevented Diesel from runmng -

387/82-59 O 1 Crushed field wire to DG oil pump 416/82-165 O 12 Unqualified cable in DG control circuitry 029/83-24 I 1 High temperature embrittlement of cable to feedwater temperature mhcator 219 83-21 O 1 DG power cable failed 237 83-40 1 1 Isolation valve cable shorted between drywell penetration and valve 245 83-26 O 1 Cable to gas turbine speed sensor failed from oil impregnating the-cable and seating 254 83 34 I 1 Recirculation pump discharge valve cable shorted 260 83-82 I 1 Cable fault due to 3reviously 263 83-6 O . 1 HPI governor coil cad wire sulation m, gouged wire to recirculation degraded pump

- 263 83-9 O 1 HPI governor coil lead wire insulation degraded 269 83-12 . O 1 Shorted cable to condenser circulating water discharge valve 289 83-2 O 1 Wire failed due to contact with a burr in MCC causing MCC to trip 302 83 51 0 1 Worn insulation to selector switch of DG led to inoperability 312 83-24 O 1 Ground fault to service water pump from apparent cable damage duringinstallation 316 83 I 1 Faulty cable caused _ ground on containment isolation valve cable 325 83-61 O '1 Defective cable toIRM 327 83 152 O 1 Bad cable to containment isolation valve 366 83-79 O 1 Broken wire to HPCI bearing temp. element 368 83-2 O 1 1/2 inch long rupture in fan motor cable-cable showed signs of internal pressure 369/83-2 I 1 Pressurizer heater cable overheated and burned, apparently due to hot resistors 369 83-81 O 1 Insulation of fire detector cable broken 370 83 51 0 1 Failed cable to rod positioning coli 373 83-143 I 1 Two cables in upper drywel damaged by beat from localized " hot 395/83-6 O 1 knng to hydrogen analyzer dama ed by heat 416/83-185 O 1 Two, wires shorted in transformer breaker handswitch causing breaker to tnp 213/84-17 O 1215 conductor reactor control instrumentation cable degraded-dried i out and slightly hardened 255/84-10 1 1 Cable damaged by high temp. resulting from enclosure in fire barrier 263/84-13 O 1 Ground fault in underground cabling to station auxiliary transformer

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265 84-1? . I' 1 IRM cable faulty' 278 84-10 O 1 Grounded leads on primary side of condensate pump transformer 311 84-18 I ' 1 Broken wire in valve operator circuit to relief valve resulted in reactor

, tnp 1 Broken wire to HPCI turbine' speed indication caused HPCIisolation -

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325 84-7. O 325 84-34 O 1 Defective cable to intermediate range monitor 373 84-18' I 1 Allegations 'of improperly installed butt splices and poor jacket removal technique causmg cuts in cable insulation-inspections / repairs performed -

L 388/84-2 -I 1 Faulty detector cable to SRM.

259/85-37. O 1 Isolation valve cables pinched and shorted 278/85 27 O 1 -Pinched wire in differential pressure indicating switch caused ground in RHR system logic 295 85-22 O 1 Pinched wires inside SI pump inlet valve 304 85-18. I 12 No EQ documentation for bmitorque wiring 338 85 O 1 Defective cable 366 85-12 O .1 Cable to main steam line radiation detector saturated with water and -

connector to a redundant detector failed 409/85-14 O 1 Grounded wire in CRD mechanism 482/85-54 O 12 Failure of a wire supplying power to a 120V instrument distribution panel 247 86-5 I 12 No EQ documentation for Umitorque wiring 249 86-8 I 13 Drywell RM cable stepped on and shorted 250 86-38 O 13 Burned motorleads on AFWvalve actuator 25186-23 O 13 Nicked insulation in cable to immersion heater coil for tube oil temperature control to DG 254 86-18 I 13 IRM cable worn and cracked 255 86-03 I 12 No EQ documentation for Umitorque wiring-259 86-03 O 13 Cable fault caused short to ground of alternate feeder to shutdown bus 260/86-08 I 13 Electrical arcing from containment ventilation valve limit switch caused by broken conduit connector and cable contact with junction box knock out 272/86-18 I .12 No EQ documentation for Umitorque wiring 1 Broken wire to isolation solenoid valve caused by initial improper 276/86-06 I stripping of wire followed by vibration 278 86-04 O 13 Two grounded wires inside RHR pump breaker  ;

280 86-20 I 12 No EQ documentation for Umitorque wiring l i

281 86-1 O 13 Failure of stress cone connection on feccer breaker caused cable short to ground 286/8610' O 13 Moisture in underground conduit caused grounds in generator transmission line disconnect switch cable 289 86 9 O 12 Cable to reactor building cooling fan not included on EQ master list 302 86-7 I 12 No EQ documentation for Umitorque wiring 316 86-16 O 13 Shorted control power wires topower range monitor drawer 322 86-28 I 12 No EQ documentation for Unutorque winng 324 86-7 O 13 Damage to lead insulation of reactor bui! ding exhaust RM caused aowerlead to ground 331/86-18 I 13 No EQ documentation for Umitorque wiring 335/86-09 O 13 Smokingisophase bus cablejumpers

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344/86-01 0 13 Cracked insulation on feedwater control valve motor operator motor shunt field lead wire 370 86-13 I 12 No EQ documentation for Umitorque wiring

' 1 397 86 19 I 12 No EQ documentation for Umitorque wiring and connections 397 86-33 O 12' Undersized wires to standby service waterpump 414 86-35 I 12 No EQ documentation for Umitorque wirmg and connections 440 86 57 1 12 No EQ documentation for Umitorque wiring and connections Cable to SRM nicked during maintenance causing control power fuse 456 86 10 0 13 to blow 1 12 No EQ documentation for Umitorque wiring and connections 458/86 8 155 87 6 I 12 Questionable EQ of butyl rubber and polyethylene cable 219 87-03 O 13 Ribbon cable for area RM nicked and degraded from age and use 261 87-7 I 12 Unidentified cable with unknown EQ status in safety re .ated circuits 261 87-20 1 13 Feedwater regulating valve cable shorted water in conduit 27 87-16' I 12 Power lead cabling to pressurizer PORV stop valve degraded-actual environment higher than expected 309 87-5 I ' 12 No EQ documentation for a cable of unexpected brand 312 87-6 I 12 Undersizepower cables to motor operators 327 87-48 I 12 Cable pullmgyractice could damage cables and result in failures

'382 87 8 O 13 Shorted wire m feedwater control system 387/87-30 O 13 Nicked wire to reed switch for Target Rock position indication shorted in containment instrument gas isolation valve 454/87-18 O 1 Broken wire to proximity sensor for feedwater pump wear annunciator 461/87-67 O 13 Fatigue failure of T/C lead wire when adjacent wire was moved for mamtenance 482/87-19 O 13 Broken shield on coaxial cable caused spike on containment purge RM 213 88 9 I 13 Nuclear instrument detector cable deteriorated 261 88-11 0 1 Degraded insulation on turbine speed arobe caused turbine trip 280 88-08 O 13 Phase to phase fault in motor leads to l ow head SI pump 395 88-01 0 13 Electrical lead pinched in distribution panel cover and shorted to IN bles not installed per EQ re 1 121 Extended 413/88-3 range neutron monitor cabuirementsle may 498/88 31 1

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y' APPENDIX B Connection Events The three searches described in' Appendix A were also used as the basis for the manual search for connection events. The related connection events are tabulated below with reference to which of the searches contained each event. Even though search I was only -

intended to identify cable-related LERs, a significant number of connection events were h

also included in this search, but not in the other searches (because of their limited

. Thus, connection events were aho tabulated while performing the cable scopes) tabulat ion, with due recognition that some connection LERs were missed for 19841985 time frame.

h LER # -I/O" Description 155 80-48 I ~ 12 150 splices and 5 terminal blocks of c questionable EQ -

259 80-34 O : 1 Loose connection on jumper wire in limitorque MOV 3

, 260 80 50 I 1 Open circuit in IRM due to bad connections 1 "

263 80-15 I 12 Unqualified splices in power cables for MSIVs e 324 80 46 I 2 Unqualified splices to SOVs 324 80-64 O 1 Annunciator relay for low reactor level alarm actuated due to excess wire grounded at termination 1 HPI governor connectorplug cracked and shorted - i 324 80 O i 325 80-11 O 1 Loose wire to control switch for HPI oil pump 331 80-35 O 1 CST low level switch failed from corrosion on probe lead wires caused by moisture also LER 81-5 335 80-5 O- 1 Loose power lead to CRD power supply 336 80-29 O 1 - Frayed insulation in connector to DG speed sensor caused ground 346 80-45 O 1 Nuclear instrumentation cable not connected completely in control room -

346/80-78 I 1 Loose solder connection to RCS pressure sensor 247 81-27 O 1 Connection to strip heater element was burned and broken off l 251 81-09 O 1 Loose crimp on coil wire to transfer inhibit relay for DG -

255 81-39 I - 1 Splices, terminal blocks, and jumper wires with questionable EQ 259 81-13 O l' Loose connection to cooling tower transformer relay 275 81-03 O 1 Separated center wire in coax connector to radwaste effluent line RM 285 81-03 O 1 Loose connection to 125 Vdc bus feeder switch caused cable to burn loose 304 81 O 1 Broken wire on Diesel tachometer caused DG to trip 304 81 28 O 1 Wire to RM flow switch relay vibrated opened 312 818- O 12 Loose connection on pigtail to trip coil for reactor building spray pump breaker would not allow breaker to trip 317/81-51 O 1 Leac. to high flow trip for RM system broke and tripped pump 318/81-18 O 1 Worn, anc abradea tape connection caused short to ground and chargmg pump to tnp 321/81-122 O 1 SBGTconnection defective 321/81-140 O l' Loose connection in rod sequence control panel caused overheating ofjumper and fuse block 324/81-91 O 1 Ambient room humidity caused short in RHR valve logic because of failure to seal electricalleads

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366/81-82 0 1 Separated wire to HPCI oil pump motor-appeared to have been cut -

and degraded from normal use 369/81-49 O 1 Power cable to waste processing panel not properly terminated 265/82-8 I 1 Broken, sensor wires and dirty contact to relief valve position .!

monitonng systems j 272/82-25 Omaintenance 12 Piece of solid wire shorted SG level transmitter-wir 1 Broken wire at a splice to SG level transmitter 281/82-41 I 1 Containment cooling unit tripped as a result of taped connection I 317/82-75 I j fraying and shorting to ground l

318/82-29 O 1 Bent detector cable to particulate RM caused five wires crimped to a l connector to pull free i 320 82-38 O 1 Loose cable plu g-loss of meteorological data 325 82-102 O 1 SRMs inoperab e-broken wire and moisture in connector 333 82-19 O 1 Broken wire at control rod selector switch 1 Water in cable and connector of excore detector from inleakage 334 82-23 1 through refueling cavity seal 334/82-42 O 1 Connection at fan motor lead burned off 2 Shorted terminal lugs to caused bad position indication of isolation 335/82-27 I SOV 1 12 Broken wire to RM at connector-improper installation led to eventual 346/82-2 failure also LER 82-13 346/82-2 1 2 Short wires to RM strained and broke-bad installation 1 Momentary short in coil lead due to water getting into control rod 250/83-05 0 power cabinet 1 Water in motor lead connection box-RHR pump inoperable 251/83-18 O 1 Breakdown of insulation tape at connections to DG lube oil 259/83-17 0 circulating pump 293 83 13 O 1 Imose wires at contact of SBGT heater-burnt wire 302 83-5 O 1 Imose connection-loss of wind speed sensing 302 83-60 0 1 Cold solder joint on indicator wires fai..ure of decay heat cooler discharge temperature monitor 315/83-74 O 12 4 cables with badly damaged and burned insulation at auxiliary transformer-due to cop,per connectors on aluminum conductors 1 Broken lead to Thot signal power supply due to stress at termination 317/83 31 O pomt 325 83 31 1 1 Defective tis,nal connectors to IRMs 327 83-19 I 1 Imose connection at reactor head for rod position indi;ator 328 83-50 1 1 Open connection to CRD lift coil 369 83-96 O 1 Bad solder joint in coaxial cable to steam line RM 395 83 34 O 1 Insulation failure to RHR pump caused by terminal lug forced against termination box cover by its own weight 395/83 39 O 1 Power loss to RM system-power lead short to ground 1 Ioose connection to DG control logic 244/84-09 O  !

250/84-11 0 1 Water in EPA canister caused inner to outer shield short in power range detector cable 259/84-23 0 1 Imose terminal due to installation of 3 wires on 1 terminal 1 Imose connection in turbine control system caused turbine and 275/84-30 0 reactor inp 280/84-02 0 1 Imose cable to semi vital bus

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3, 281/84 'O 2 RHR pump 4160 V motor leads had 1000 V heat shrinkable material 029 85 7- O 2 loose solder terminals to power range monitor 251 85-21 O 11 Bad Heat electrical at CRD mechanism caused rod drop .

from loose connection caused cable insulation to be dry and 259 85-51 0 cracked in RPS panel-277/85-28 O .1 Stray strands of wire at connection in contact with de voltage caused fuse to blow-302 85 28 O 1 Imose connection on motor breaker caused 6900 V bus fault 311 85 9 O 2 High resistance connection in CRD cable 315 85-46 O.1 Instrument bus circuit breaker tripped as a result of inadequately terminated lead 316 85-4 1 2 RCS RTD connection not qualified 327 85 34 O 2 DG connector loose from controls to governor hydraulic actuato:-

362 85 34 O 1 Loose connection to fuel storage pool RM 366 85-34 O 1 Power feeder to RPS breakers burned in two at connection 370 85-17 O 1 Doghouse level switch control circuitry connection and relays corroded-reactor trip 374 85-22 I 1 Very loose penetration cable to IRM 388 85 18 O 1 Imose connections to RPS breakers caused trip 416 85 30 O 1 Faulty instrument plug connector to generator cooling water flow transmitter 454 85-86 1 2 Unc ualified terminal strips to MSIVs 482 85 54 O 12 Faulty crimxd connection to 120 V instrument distribution panel 483 85-7 I 2 UnqualificcL tbs in MOVs 247/86-35 O 13 Imose connections in circuitry to RPS relays 3 Corro 251/86-18 O AFW valve 254 86-37 I 2 Butt splices used at EPA failed EO test 260 86 12 0 13 loose internalwire in breaker 261 86-02 0 3 loose connection on test jack for SG level transmitter 272 86-06' I 13 Broken wire associated with a series solenoid isolation va feedwater 272/86-7 I 2 Unqualified connectors to SOV in post accident sampling system 272/86-15 I 3 Raychem splices not installed as required for EO analysts indicated acceptability 3 loose connections in reactor trip switchgear 275/86 10 O 3 Corrosion caused poor electrical connection in feedwater control j 278/86-20 O system,resultingin scram 278/86-24 O 13 Imose connection for RCIC temperature switch caused closure o RCIC steam supply valves 280/86-35 I 12 Improper installation of Raychem heat shrink tubing 281/86-01 O 13 Improper installation of stress cone connection on transformer fe breaker 281 86-18 I 13 Improper installation of Ra chem heat shrink tubing 282 86-07 I 13 Improper installation of Ra chem heat shrink tubing 286 86-08 I 13 Improper installation of Ra chem heat shrink tubing I

293 86 10 O 2 loose wires to Primary Containment Isolation /RPS 295 86-26 I 13 Improper installation of Raychem heat shrink tubin 295 86-40 environment EQ 309/86-07 O 13 loose connection on control oil pump to main turbine caused trip '

312/86-11 O 2 Loose terminations inside Bailey cabmets

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y' 316/86 O 13 Faulty connector caused shorting in power range monitor drawer 324/86-04 O 3 Shortmg of solder connection penetrating the backplate of a control room panel' 324 86-07 O 13 Damage to lead insulation sheathing caused shorting and RM trip 324 86-12 O 3 Isose connection to RWCU temperature switch

-324 86-14 I 13 Oxidized coaxial connections on five signal cables to IRMs 324 86-23 O 3 loss of continuity at T/C connections for HPI isolation instruments -

325/86-30 O 13-Motor generator set breaker trips from high resistance connection at breakers 328/86-03. .O 13 Imose connection in junction box between alarm and iodine low sample flow switch 333 86 17 I 3 RM connectors dirty or wet also broken connector 344 8611 O 13 Imose connection on main turbine vibration sensor caused trip 346 86-21 I 13 Improper installation of cable splices 362 86-08 I 13 Faulty wire on detector / preamp assembly connector to containment airborne gas monitor 374 86-02 O 3 loose torque switch connection on RCIC steam line isolation valve 374 86-13 I 2 SOV termmations not installed as required for EO 374 86-14 1 2 O,konite tape terminations not analyzed for use over Kapton insulated wire 387/86-11 I 13 Broken shield on SRM cable at detector connection 388/86-13 I 13 Faulty connectors at EPA to IRM 395/86 11 O 3 Oxidation inside SOV connector-caused feedwater isolation valve to close and reactor trip 397 86-37 I 12 Connector to acoustic monitor not qualified 410 86-24 O - 3 Corrosion on battery bus bars and terminals 414 86-4 O 13 Wire to solid state protection system switch insufficiently connected 458 86-39 O 3 Inadvertent fire protection system actuation caused water accumulation in beanng vibration probe for main turbine, resulting in scram 461/86-19 O ' 2 Bad connection and ground problem at control room RM detector interface box 482/86-43 7 12 No EQ documentation for wiring and terminals in MOVs 155 87-8 I 12 23 unqualified splices to valve position indicating circuits 206 87-6 I 2 Butt splices of non-qualified configuration 206 87-18 O 3 Moisture at solenoid connections caused ground indication on DC bus 219 87 11 0 13 Maintenance ersonnel inadvertently disconnected termination that wereimprope yinstalled l 219/87-13 O 2 Connector fel off recently installed power supply 219/87 22 I 3 Failure of a cable splice from coaxial cable to twisted shielded pair on relief valve position indicator l 219/87-35 O 3 Loose ground connection onIRM middle conductor on BNC connector to input of particulate l

244/87-05 I 12 {rget 247/87 28 O 1 Moisture found on the electrical leads to gas and particulate monitor sample pump motor 251 87-15 I 3 Shorted wire at solenoid from deteriorated insulating tape 251 87-19 O 2 Imose solder joint to RPI caused spurious indication 254 87 3 O 2 loose solder joint in RCIC flow controller 254 87-6 O 3 Imose soldered connection on HPI reset solenoid

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74 255/87-02 I 3 Highly corroded connector pin at nuclear instrumentation detector

~e lement 259 87-05 O 3 Burned electrical connection between power boost current transformer and voltage regulator of DG

'259 87 07 O 3 Broken terminallug and loose connection to control room inlet RM 261 87-3 I 12 Questionable splice to power lead of SI valve 277 87-19 O 13 ' RHR pump trip caused by loose connection at fuse ,

298 87-03 O 13 Connections to feedwater flow recorder loose 309 87-3 'I 2 Unqualified splices to TCs and RTDs 309 87-5 ' I - 12 Terminal block found where a splice was rec uired I 312 87 42 O 3 Electrical contact problems with Amphenolilue ribbon connectors 316/87-15 I 3 Power range detector high voltage cable connector separated from cable after routine calibration 317/87-7 I 2 Unqualified taped splices to SOVs 317/87-13' O 3 Trip caused by loose connection on breaker which' controls reactor

< coolant pump starts 321/87-02 O 13 Trip caused by loose wire and conductive film on cable to main generator pound fault detector 322/87-05 0 113 Worn cab;e and connection to meteorological delta temperature sensors-alsoI.ER 87-28 322/87-35 O 13 Grounding problem in primary containment monitoring panel 328/87-08 I 13 Poor ground on air RN detector cable 1 Loose connection to RCIC isolation valve power supply caused valve 331/87-27 O to close 341/87-31 O 3 Faulty connection to shaft rider vibration sensor on main turbine

. generator 341 87 1 2 7 improperly installed heat shrink terminations 344 87 9 I 2 Excessive bending radius of Raychem splices to PORV SOVs 344 87-37 O 3 Imose connection in auto-start circuitry for turbine driven AFW pump 352 87-15 O 13 HPCI turbine shutdown-loose flowcontrollerlead

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352 87-40 O 3 Faulty connection to electro hydraulic controllogic board 352 87-41 O 13 Imose connection to RM 354 87-51 0 13 Bad connection and degraded cable in main steam line RM drawer 361 87-28 I 3 High impedance connection in RM from deposits 361 87-31 O 3 Corrosion of power leads and terminal block to main feedwater isolation valve 362/87-11 O 3 uninterruptible loose bolt connection from instrument bus to main bus of non power supply intermittent loss of continuity O 12 Poor electrical contact at aluminum setscrew-type terminal lug to 368/87-7 instrumentation distribution transformer 370/87-16 O 3 Grounded motor lead connector on instrument air compressor due to insulating tape wear 373 87-26 O 2 RHR motor terminations not installed as required for EO lices 4

395 87-25 I 12 Possiblyunqualified ta 400 87-1 O 12 loose connections on CRD position indication i 412 87-22 O 13 Faulty connection to 413 87-15 O 3 Trip caused by moisture in a terminal box caused fuse to blow for mam feedwater isolation 423/87-10 1 13 Imose plug connecting loose parts monitoring sensor coaxial cable to preampli5er 440/87-25 I 13 loose signal common connection to vessel pressure sensor 455/87-01 1 3 Poor sphce connection to reactor coolant RTD

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456/87-32 O 3 loose connections in disconnect switch in rod control system power cabinet 461/87-07 I 13 10 Kn short in control circuitry caused actuation of SRV 461/87-43 0 3 Loose connection on the turbine trip vibration detection circuitry caused scram 461/87-66 I 3 156 electrical junction boxes and panels found without drain holes as required for EQ 482/87-19 O 13 Broken shield on coaxial cable connector to containment purge exhaust RM  !

482 87-22 O 3 Trip caused by loose connection at breaker for turbine building fan 482 87-37 O 13 High resistance and heating at bolted T-pad connection 482 87-52 I 2 Terminations on instrument circuits not mstalled as required for EQ 482 87 54 O 3 Moisture induced corrosion of a connector to containment atmosphere RM 482/87-58 I 3 Contamment area RM connections not installed as required for EQ 244 88-01 I 3 Faulty connections at SRM 259 88-01 I ' 3 1.oose solder connection in temperature switch 265 88-09 O 1 Five high resistance connections in station battery connections reduced capacity to 58%

395/88-02 O 3 Poor design allowed loosening of test board terminal posts for power range momtor-plant tnp 413/88 5 I 2 Buchanan terminal blocks potentially not qualified for use in MOVs inside containment 416/8810 O 13 Trip caused by loose connection which deenergized scram pilot solenoids 458/88-06 O 3 Flashover from phase to ground due to moisture intrusion from a leaking service water valve resulted in recirculation pump motor trip 483/88-03 I 3 Contamment area RM connections at EPA not installed as required for EQ 498/88-4 O 2 Loose connection to control room toxic gas monitor 498/88-8 I 12 Improper installation of cable splices 1

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t APPENDIX C EPA Events  !

IFR # Description f

255 80-8 1. caking EPA--cause not determined-also LER. 83 66 261 80-14 EPA's with PVC insulation-no EO data on PVC 285 80-7 No LOCA qualification for splices to EPA -

285 80 11 Excessive EPA leakage l 409 80-1 Cracked EPA glands-leak rate exceeded 029 81-13 Excessive leakage due to loose flanges on Chica o Bridge and Iron EPA 270 81-2 MV EPA cracked inboard insulation bushing S 6 loss-also LER 81-14. s 328 81-138 Defective EPA cable conductor to reactor coolant pump thrust bearing temperature monitor 280 82-92 Faulty rod position indication due to EPA exposure to excessive moisture ,

346 82-35 Degradation on insulation to SRM in EPA module 409 82-11 3 cracked EPA glands-leak rate exceeded 348/83-7 Excessive leakage due to cracked metal "O"-ring-probably occurred during repair during previous outage 362/83-65 Faulty EPA to high range radiation monitor 409/83-2 Cracked EPA glands-leak rate exceeded 281/84-05 Water in electrical penetration to motor leads of reactor coolant pump caused pump to trip 285/84 9 EPAs failed qualification test 271/85-10 6 GE EPAs-potential shorting due to sharp edges on EPA assembly, reported shorts  ;

348/85-12 Short in EPA to control rod grippers caused supply fuse to blow and reactor trip also LER 86-4 348/85-16 Shorts in GE EPA's,14 of 55 modules had shorts between adjacent pairs 247/86-13 Discovered a circuit that could become submerged during LOCA conditions not qualified to function rerouted circuit in another EPA 249 86-24 EPA's with butt splices failed EO tests because of excessive leakage 254 86-37 EPA's with butt splices failed EO tests because of excessive leakage 348 86-8 Electrical shorts m GE penetrations 206 87-10 Installation damage to pigtails of penetration 344 87-11 Excessive leakage past conductor seals-permanent compression set of seals 213/88-6 Flooding could cause submergence of terminal blocks connected to EPA

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From Nuclear Power Experiences:

c D. ate Plant Description 11 DRES 2 Cracks in inner epoxy seal GE 5-74 10 77 HATCH 1 Failed MILL 2 Electrical sealsadjacent faults between around conductors conductors (G (GE 100 serie 9-77 MILL 2 I.ow IR's adjacent conductors-moisture intrusion 10 79 COOK 1 Faulty Westmphouse containment cable penetration 10 80 SEO 1 RTD lead resistance excessive-faulty penetration with defective lead 7-72 SURRY1 Heat generation in EPA connector-degradation and failure with loss of pressure seal at interface

\ 10 75 OCON 2 Cracked insulation bushing-exterior side SF6 loss 10 76 OCON 2 Cracked insulation bushing-reactor side SF4 loss

'73 '75 OCON Units 1-3 EPAs leaking i.ange-scal corrosion; MV EPA's stress on -

bushings caused cracking of in & out board insulating seals

'60 '65 YAN RO leaking inner scal de: ective inner seal moisture intrusion field manufactured unit 11-75 YAN RO Cracked glands on MI cable excessive outward pressure General

. seal 7-81 Various Cable Catawba Corp 1 &2, McGuire 1&2, and Yankee Rowe-EQ test shows potential for connector insulation on D. G. O'Brien EPA to expand.

and strip cable insulation, causing electrical shorts-connectors have been redesigned 1

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