Nuclear Power Plant Electrical Cable Damageability Experiments (NUREG/CR-2927, SAND82-0236)
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Manuscript Completed: October 1982
Date Published: October 1982
Larry L. Lukens
Sandia National Laboratories
Albuquerque, New Mexico 87185
Operated by Sandia Corporation
for the U.S. Department of Energy
Under Contract No. DE-AC04-76DP00789
Division of Engineering Technology
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001
Under Memorandum of Understanding DOE 40-550-75
NRC FIN A-1010-2
Under the direction of the Nuclear Regulatory Commission, Sandia National Laboratories has been conducting confirmatory research in fire protection for nuclear power plants. As a part of this research, a program was developed to determine the damageability of electrical cable insulation to thermal radiation in a loaded cable tray. The critical flux or threshold level at which cable damage occurs in the form of electrical failure (short from conductor to tray) and nonpiloted ignition was determined for two types of electrical cable, one an IEEE-383 qualified cable and the other an unqualified cable. The critical flux for electrical failure was determined to be about 18 kW/m 2 for the IEEE-383 qualified cable and about 8 kW/m2 for the unqualified cable. The critical flux for nonpiloted ignition was determined to be about 28 kW/m2 for the IEEE-383 qualified cable and about 22 kW/m2 for the unqualified cable.
A program was also developed to determine the damageability of electrical cable insulation to constant temperature, thermal exposure. Experimental results indicate that exposure of the IEEE-383 qualified cable to temperatures greater than 250 °C (480 °F) for periods of 60 minutes can cause discoloration, blistering, smoking, loss of flexibility, and failure to pass a voltage withstand test as described in the report. Experimental results indicate that exposure of the unqualified cable to temperatures greater than 130 °C (265 °F) for periods of 60 minutes can cause electrical failure in the form of shorts between conductors. In addition, the thermal forming temperature of the unqualified cable jacket material was determined to be between 170 °C (340 °F) and 200 °C (390 °F).
These results apply only to the two particular types of electrical cables examined and described in this report, and would need to be evaluated for any other type of electrical cable. Thermal aging and radiation exposure efforts were not included in the investigation.