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HomeNRC LibraryDocument CollectionsGeneral CommunicationsInformation Notices1993

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                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C.  20555

                               April 28, 1993


NRC INFORMATION NOTICE 93-33:  POTENTIAL DEFICIENCY OF CERTAIN CLASS 1E 
                               INSTRUMENTATION AND CONTROL CABLES


Addressees

All holders of operating licenses or construction permits for nuclear power
reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to a potential deficiency in the environmental
qualification of certain Class 1E instrumentation and control cables.  It is
expected that recipients will review the information for applicability to
their facilities and consider actions, as appropriate to avoid similar
problems.  However, suggestions contained in this information notice are not
NRC requirements; therefore, no specific action or written response to this
notice is required.

Description of Circumstances

Sandia National Laboratories, under contract to the NRC, tested cables to
determine the long-term aging degradation behavior of typical instrumentation
and control cables used in nuclear power plants and to determine the potential
for using condition monitoring for assessing residual life.  The results of
this testing are described in NUREG/CR-5772, "Aging, Condition Monitoring, and
Loss-of-Coolant Accident (LOCA) Tests of Class 1E Electrical Cables," Volumes
1, 2, and 3.  The tests were conducted on cross-linked polyolefin/poly-
ethylene, ethylene propylene rubber, and miscellaneous Class 1E cable types. 
The test program generally followed the guidance of Institute of Electrical
and Electronics Engineers (IEEE) Standard 323-1974, "IEEE Standard for
Qualifying Class 1E Equipment for Nuclear Power Generating Stations," and IEEE
Standard 383-1974, "IEEE Standard for Type Test of Class 1E Electric Cables,
Field Splices, and Connections."  IEEE Standard 323-1974 is an industry-
established standard endorsed by the NRC for qualifying Class 1E equipment for
nuclear power generating stations, and IEEE Standard 383-1974 is an industry-
established standard for type test of Class 1E electric cables, field splices,
and connections for nuclear power generating stations. 

The test program consisted of two phases; both phases used the same test
specimens.  Phase 1 consisted of simultaneous thermal and radiation aging of
the cables at approximately 100 C (212 F) and 0.10 kGy per hour (10 kilorads
per hour), respectively.  Three different sets of cable specimens were tested
in this phase:  one was aged to a nominal lifetime of 20 years, a second to 
40 years, and a third to 60 years.  Phase II was a sequential accident
exposure consisting of 1100 kGy (110 megarads) of high-dose-rate irradiation

9304230163
.

                                                            IN 93-33
                                                            April 28, 1993
                                                            Page 2 of 4


at the rate of 6 kGy per hour (600 kilorads per hour) followed by a simulated 
 exposure to LOCA steam.  The test profile was similar to the one given in
IEEE Standard 323-1974 for "generic" qualification.  The cables were energized
at 110 V dc during the accident simulation.  Insulation resistance was
measured on line throughout the test.  No chemical spray was used during the
steam exposure, but a post-LOCA submergence test was performed on the cables
that were aged to a nominal equivalent of 40 years.

Cable types that failed during the accident tests or that exhibited marginal
insulation resistances were Rockbestos Firewall III, BIW Bostrad 7E, Okonite-
Okolon, Samuel Moore Dekoron Dekorad Type 1952, Kerite 1977, Rockbestos 
RSS-6-104/LE Coaxial, and Champlain Kapton.  The list of cables included in
the test program and a summary of the test results from NUREG/CR-5772 are
shown in Attachments 1 and 2, respectively. 

In addition, the Sandia National Laboratories (under contract to NRC) has also
tested cables in a separate program to determine the minimum insulation
thickness necessary for installed cable to perform its intended function
should the insulation be damaged during installation, maintenance, or other
activities.  During LOCA testing, all 10 of the Okonite-Okolon cable samples
failed.  The results of this test program are summarized in NRC Information
Notice 92-81, "Potential Deficiency of Electrical Cables With Bonded Hypalon
Jackets," issued on December 11, 1992.

Discussion

The Sandia National Laboratories test results from NRC-sponsored programs
raise questions with respect to the environmental qualification (EQ) of
certain cables that either failed or exhibited marginal insulation resistance
values.  The staff reviewed the test data and noted that cable types
identified as Firewall III, Okonite, Dekorad, and Kapton failed during the
simulated accident exposure, while BIW Bostrad, Rockbestos Coaxial, and Kerite
exhibited marginal insulation resistances.  It should be noted that the
insulation resistance of the Rockbestos coaxial cables may be too low to meet
specifications for use in General Atomics radiation monitor circuits,
depending on the environment to which the cable will be exposed.  The low
insulation resistance of these Rockbestos coaxial cables was the subject of a
10 CFR Part 21, "Reporting of Defects and Noncompliance," notification by
General Atomics dated March 28, 1989.

As part of the NRC-sponsored aging research program, the Sandia National
Laboratories searched licensee event reports (LERs) to find LERs that might be
related to cable aging.  In NUREG/CR-5461, "Aging of Cables, Connections, and
Electrical Penetrations Assemblies Used in Nuclear Power Plants," the Sandia
National Laboratories concluded that although cables are highly reliable 
.

                                                            IN 93-33
                                                            April 28, 1993
                                                            Page 3 of 4


devices under normal plant operating conditions, with no evidence of 
significant increases in failure rate with aging, the performance experience
with these components under actual accident conditions is small.  The current
LER data provide a very limited database for this purpose.  The only
significant data for cables subjected to design-basis events comes from EQ
testing.

Depending on the application, failure of these cables during or following
design-basis events could affect the performance of safety functions in
nuclear power plants.  NRC Generic Letter 88-07, "Modified Enforcement Policy
Relating to 10 CFR 50.49, `Environmental Qualification of Electric Equipment
Important to Safety for Nuclear Power Plants'," provides relevant information
on dealing with potential EQ deficiencies.  In Generic Letter 88-07, the NRC
stated, in part: 

      When a potential deficiency has been identified by the NRC or licensee
      in the equipment (i.e., a licensee does not have an adequate basis to
      establish qualification), the licensee is expected to make a prompt
      determination of operability (i.e., the system or component is capable
      of performing its intended design function), take immediate steps to
      establish a plan with a reasonable schedule to correct the deficiency,
      and have written justification for continued operation, which will be
      available for NRC review.

      The licensee may be able to make a finding of operability using analysis
      and partial test data to provide reasonable assurance that the equipment
      will perform its safety function when called upon.  In this connection,
      it must also be shown that subsequent failure of the equipment, if
      likely under accident conditions, will not result in significant
      degradation of any safety function or provide misleading information to
      the operator.
.

                                                            IN 93-33
                                                            April 28, 1993
                                                            Page 4 of 4


This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.


                                       ORIGINAL SIGNED BY


                                    Brian K. Grimes, Director
                                    Division of Operating Reactor Support
                                    Office of Nuclear Reactor Regulation

Technical contacts:   Paul Shemanski, NRR
                      (301) 504-1377

                      Ann Dummer, NRR
                      (301) 504-2831

                      Satish Aggarwal, RES
                      (301) 492-3829

Attachments:  
1.  "Cables Included in the Test Program"
2.  "Summary of Tested, Failed, and Marginal Insulation
       Resistance Cables"
3.  List of Recently Issued NRC Information Notices
.

                                                            Attachment 1
                                                            IN 93-33
                                                            April 28, 1993
                                                            Page 1 of 1


                     CABLES INCLUDED IN THE TEST PROGRAM


                                                                             

      Supplier                            Description

1.    Brand Rex   30 mil XLPE Insulation, 60 mil CSPE Jacket, 12 AWG, 3/C,
                  600 V 

2.    Rockbestos  Firewall III, 30 mil XLPE Insulation, 45 mil Neoprene
                  Jacket, 12 AWG, 3/C, 600 V

3.    Raychem     Flamtrol, 30 mil XLPE Insulation, 12 AWG, 1/C, 600 V

4.    Samuel      Dekoron Polyset, 30 mil XLPO Insulation, 45 mil CSPE Jacket,
      Moore       12 AWG, 3/C and Drain, 600 V

5.    Anaconda    Anaconda Y Flame-Guard FR-EP, 30 mil EPR Insulation, 45 mil
                  CPE Jacket, 12 AWG, 3/C, 600 V

5a.   Anaconda*   Anaconda Flame-Guard EP, 30 mil EPR Insulation, 15 mil
                  Individual CSPE Jackets, 45 mil Overall CSPE Jacket, 12 AWG,
                  3/C, 1000 V

6.    Okonite     Okonite-Okolon, 30 mil EPR Insulation, 15 mil CSPE Jacket,
                  12 AWG, 1/C, 600 V

7.    Samuel      Dekoron Dekorad Type 1952, 20 mil EPDM Insulation, 10 mil
      Moore       Individual CSPE Jackets, 45 mil Overall CSPE Jacket, 16 AWG,
                  2/C TSP, 600 V

8.    Kerite      Kerite 1977, 70 mil FR Insulation, 40 mil FR Jacket, 12 AWG,
                  1/C, 600 V

8a.   Kerite      Kerite 1977, 50 mil FR Insulation, 60 mil FR Jacket, 12 AWG,
                  1/C, 600 V

9.    Rockbestos  RSS-6-104/LE Coaxial Cable, 22 AWG, 1/C Shielded

10.   Rockbestos  30 mil Firewall Silicone Rubber Insulation, Fiberglass
                  Braided Jacket, 16 AWG, 1/C, 600 V

11.   Champlain   5 mil Polyimide (Kapton) Insulation, Unjacketed, 12 AWG, 1/C

12.   BIW**       Bostrad 7E, 30 mil EPR Insulation, 15 mil Individual CSPE
                  Jackets, 60 mil Overall CSPE Jacket, 16 AWG, 2/C TSP, 600 V

                                                                             

*  This cable was only used for the multiconductor samples in the 3-month 
     chamber.
** The IR values in BIW Report B915 are approximately one order of  
     magnitude higher than the values observed during the Sandia National 
     Laboratories testing..

                                                            Attachment 2
                                                            IN 93-33
                                                            April 28, 1993
                                                            Page 1 of 1



                     Summary of Tested (T), Failed (F),
               and Marginal Insulation Resistance (IR)* Cables


                Pre-aged 20 years           40 years               60 years
Cable Type          T--F/IR                 T--F/IR                T--F/IR

Firewall III      M  3--0/0                  3--0/0                 6--1/0

Brand Rex         M  3--0/0                  3--0/0                 3--0/0

Polyset           M  3--0/0                  3--0/0                 6--0/0

Raychem           S  2--0/0                  2--0/0                 3--0/0

Anaconda          M  6--0/0                  6--0/0                 6--0/0

Anaconda          S  1--0/0                  1--0/0                 1--0/0

BIW Bostrad       M  2--0/2                  2--0/2                 4--0/4

BIW Bostrad       S  2--0/1                  2--0/2                 2--0/2

Okonite           S  3--0/0                  3--0/0                 4--1/0

Dekorad           M  4--1/0                  4--0/0                 4--2/0

Dekorad           S  2--0/0                  2--0/0                 2--0/0

Kerite            S  2--0/0                  2--0/2                 3--0/3

Coaxial           S  2--0/2                  2--0/2                 2--0/2

Silicone          S  2--0/0                  2--0/0                 2--0/0

Kapton**          S  2--1/0                  2--1/?                 2--1/0

Totals              39--2/5                39--1/8               50--5/11

*     Minimum IR lower than 2500 ohm-1000 ft for instrument cable, 500 ohm-
      1000 ft for control cable, or 10E7 ohm-1000 ft for coaxial cable.

**    Failed cables that were pre-aged to 40 and 60 years were damaged prior
      to accident test.

?     No IR measurements were possible.

S     Single conductor cables

M     Multiconductor cables
.
```

*Page Last Reviewed/Updated Thursday, March 29, 2012*

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