Information Notice No. 93-33: Potential Deficiency of Certain Class 1E Instrumentation and Control Cables
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
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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
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April 28, 1993
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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.
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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
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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
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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
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