United States Nuclear Regulatory Commission - Protecting People and the Environment

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. 
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