Bulletin 77-05: Electrical Connector Assemblies
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D. C. 20555
November 8, 1977
IE Bulletin 77-05
ELECTRICAL CONNECTOR ASSEMBLIES
Description of Circumstances
Recent tests conducted by the Sandia Laboratories of electrical
connector/cable assemblies in a simulated post-LOCA containment environment
(LWR) demonstrated that the assemblies, failed to perform in an acceptable
manner. The connectors are the pin and socket type, with metal shell and
screw couplings. The specific test specimens were manufactured by Bendix,
ITT Cannon and Gulton Industries using combinations of Anaconda and ITT
Surprenant cables. Details of the specific connector/cable combinations,
test conditions, test results and other pertinent information are described
in the Attachment.
While electrical connectors of the type tested are not normally used in
applications that are required to survive LOCA conditions, it is not
possible in the absence of specific information to conclude that such
applications do not exist. Further, it is unknown whether other
manufacturers have supplied similar assemblies, whether such assemblies have
been properly qualified for the intended service, or whether these types of
assemblies are utilized in applications that must continue to operate
reliably in a LOCA environment.
Action To Be Taken By Licensees and Permit Holders:
For all power reactor facilities with an operating license or a construction
permit:
1. Determine whether your facility utilizes or plans to utilize electrical
connector assemblies of the type tested by Sandia Laboratories, or any
other similar type, in systems that are located inside containment, are
subject to a LOCA environment and are required to be operable during a
LOCA.
2. If any such applications are identified, review the adequacy of
qualification testing for the assemblies and submit the documentation
for NRC review.
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IE Bulletin 77-05 November 8, 1977
3. If evidence is not available to support a conclusion of adequacy,
submit your plans and programs toward qualifying existing equipment or
your plans for replacing unqualified assemblies with qualified
equipment.
4. Provide your response in writing within 30 days for facilities with an
operating license and within 60 days for facilities with a construction
permit. Reports should be submitted to the Director of the appropriate
NRC Regional Office and a copy should be forwarded to the U. S. Nuclear
Regulatory Commission, Office of Inspection and Enforcement, Division
of Reactor Construction Inspection, Washington, D. C. 20555.
Approved by GAO, B180225 (R0072); clearance expires 7-31-80. Approval was
given under a blanket clearance specifically for identified generic
problems.
Attachment:
Trip Report by W. R. Rutherford
Electrical Connector Assemblies
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IE Bulletin-77-05
November 8, 1977
TRIP REPORT
by
W. R. Rutherford
ELECTRICAL CONNECTOR ASSEMBLIES
On September 1, 1977 a meeting was held in Alburquerque, New Mexico to
investigate the electrical connector assembly malfunctions or failures that
occurred during tests under LOCA conditions performed by Sandia
Laboratories. The following is a description of the equipment, test scope
and results of these tests.
Equipment
The test assemblies of particular interest consisted of three types of
connectors: Bendix, ITT Cannon, and Gulton installed on two types of cables;
Anaconda and ITT Surprenant.
1. Bendix Connector: A 3 conductor/No. 12 AWG with crimp pin conductors,
anodized aluminum shell, silicone rubber insert, rigid back plane,
potting, pliable over-potting.
2. ITT Cannon Connector; A 3 conductor/No. 12 AWG with crimp pin
conductors, anodized aluminum shell, silicone rubber inserts anodized
aluminum back shell, rubber packing boot, mechanical retaining clamp.
3. Gulton Connector: A 3 conductor/No. 12 AWG with crimp pin conductor,
stainless steel shell, hard fiber insert, pin back sealed with RTV 112,
stainless shell, back plane poured with Sylgard potting, mechanical
clamp termination.
4. Anaconda Cable: A 3 conductor/No. 12 AWG, tinned copper conductor, 30
mil ethylene propylene rubber insulation 15 mil Hypalon jacket, cable
asbestos tape, 60 mil Hypalon Jacket, rated 600 volts, cable diameter
0.55".
5. ITT Surprenant Cable: A 3 conductor/No. 12 AWG, tinned copper
conductor, 30 mil Exane II insulation, silicone glass tape, 65 mil
Exane jacket, rated 600 volts, cable diameter 0.455".
Attachment A
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IE Bulletin-77-05
November 8, 1977
Test Scope
The three tests performed by Sandia were composed of two sequential and one
simultaneous exposure to LOCA environments. In each case the equipment was
exposed to radiation and thermal aging prior to operating under the
simulated LOCA conditions. Figures 1 and 2 describe the test profiles for
sequential and simultaneous tests respectively (Sandia tests were designed
to study synergistic effects). Each of the tests satisfy the intent of IEEE
323-1974. The assemblies were electrically loaded to 20 amperes and 600
volts at the start of the tests. Insulation resistance and capacitance
measurements were recorded during the tests to indicate damage.
The equipment assemblies with respect to the sequential and simultaneous
tests performed were as follows:
1. Sequential Tests (Two)
Gulton Connector/ITT Cable 1 Assembly
Gulton Connector/Anaconda Cable 1 Assembly
Bendix Connector/ITT Cable 2 Assemblies
ITT Connector/ITT Cable 1 Assembly
2. Simultaneous Test (One)
ITT Connector/ITT Cable 1 Assembly
Bendix Connector/ITT Cable 1 Assembly
Bendix Connector/Anaconda Cable 2 Assemblies
Test Results
Both ITT Cannon connector assemblies and both Gulton connector assemblies
showed almost immediate damage in terms of insulation resistance and
capacitance as the 70 psig steam was applied.
The ITT Cannon connector assembly failures appeared to be back plane boot
seal leakage failures. The assembly construction did not contain potting
compound (by design) to protect the pin backs. Therefore, boot failure leads
directly to connector failure.
In the case of the Gulton Assemblies, failures were attributed to both the
mating surface interface and the back plane seal. The design uses a rigid
insert around the mating pins and the O-ring seals are
Attachment A
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IE Bulletin-77-05
November 8, 1977
bypassed by an alignment key slot. This design may lead to leaks due to
non-uniform confinement of the O-ring which could cause arcing between pins.
Neutron radiography revealed inadequate amounts of potting compound (voids)
and cracking of potting compound. These conditions could account for back
plane failures. Neutron radiography performed on untested connectors
revealed similar conditions, i.e., voids and cracking, thus indicating an
apparent quality control problem at Gulton's facility. Other problems
detected were identified as:
1. The shrink tube used over the pin cable interface was split length-wise
and had pulled away.
2. The potting material showed virtually no adhesion to, or sealing
between, the cable jacket, insulation, and the connector shell.
3. The mechanical clamp had been secured so tightly that it cut the cable
jacket.
The Bendix connector assembly was the only type to survive an entire test
cycle. One Bendix/Anaconda assembly malfunctioned after about eight days
into the 10 psig profile and the Bendix/ITT assembly experienced decreasing
resistance and increasing capacitance through the simultaneous tests until
both readings were off scale at the end of the 10 psig profile. A second
Bendix/Anaconda assembly survived the simultaneous tests. During the
sequential tests only Bendix and ITT Cannon assemblies were involved and
both assemblies failed. The failures of these assemblies would be difficult
to define as either connector or cable failures. The ITT cable exhibited a
shrinking characteristic which could have provided a leak path through the
sealing medium of the connector.
Page Last Reviewed/Updated Tuesday, March 09, 2021
Page Last Reviewed/Updated Tuesday, March 09, 2021