Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS: 6835
Accession No.:
8202040111
IN 82-03
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
March 4, 1982
Information Notice No. 82-03: ENVIRONMENTAL TESTS OF ELECTRICAL TERMINAL
BLOCKS
Discussion:
This information notice pertains to the results of NRC sponsored research
conducted on electrical terminal blocks (type CF-1518 and CR 29605 General
Electric and type FWM States). These may be typical of those utilized in
many nuclear power plants. The research program was conducted at Sandia
Laboratories in Albuquerque, NM and consisted of approximately 600
individual tests made on enclosed and open terminal blocks of the type used
at TMI-2. The terminal blocks were subjected to 100% humidity conditions at
186oF which were the conditions experienced by some terminal blocks during
the TMI-2 accident. (Note: To date, there has been no evidence of terminal
block failure at TMI-2 during the TMI-2 accident or after). No tests at
other LOCA conditions were conducted. Terminal block performance under the
test conditions was measured by monitoring electrical terminal to ground
leakage current with terminal to ground voltage of 120, 240 and 480 volts.
Some terminal blocks were installed in metal enclosures with a 6 mm pressure
relief hole. These metal enclosures were mounted in a horizontal plane
during the tests. Some tests were made by simulating chemical spray and
various contaminants that may be found on terminal blocks and could result
in electrolytic leakage paths in nuclear power plants. The results of these
tests indicated instances of leakage currents when blocks were directly
exposed to chemicals and steam.
The NRC recognizes that the use of properly designed terminal blocks inside
containment is an option of the applicant. NRC requires qualification of
all electrical connections, cable splices as well as terminal blocks, for
accident conditions.
It is recognized that cleanliness of terminations and terminal blocks in
circuits important to safety is of concern to designers, constructors, and
licensees. The cleanliness aspects are addressed in Appendix B of 10 CFR
50. These regulations require the licensee to establish appropriate
procedures based upon manufacturer's and constructor's recommendations,
operating experience, and specific component characteristics to assure that
equipment is stored, installed, and maintained in an acceptable state. To
this end, IEEE-336, ANS 3.2, and ANSI 45.2.3 Standards and NRC Regulatory
Guide 1.39 are being used by designers, constructors, and operators of power
plants which address the installation, cleanliness, and on-going maintenance
of Class 1E electrical components, including terminal blocks.
.
IN 82-03
March 4, 1982
Page 2 of 2
In view of the above, licensees are reminded that the plant preventive
maintenance program in use at their facilities should assure (1) proper
operation of all essential components is achieved throughout the life of the
plant; and (2) that periodic inspection of those terminations and terminal
blocks for cleanliness and installation integrity is performed following any
maintenance activity affecting them.
The Office of Inspection and Enforcement has general inspection procedures
which are used by inspectors to monitor compliance with the above Standards,
Guides, and recommendations. Terminal blocks are specifically identified as
an example of a component which must be inspected for cleanliness during
construction of the power plant.
No specific action or response is required at this time. If you have any
questions regarding this matter, please contact the Regional Administrator
of the appropriate NRC Regional Office.
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