A Capacitive Sensor for Nuclear Power Plant Cable
Publication: Publication Date: 30 September 2016
A capacitive sensor was designed and tested for
the purpose of monitoring nuclear power plant
(NPP) cable degradation. The sensor was designed
as two copper interdigital electrodes printed on a
polymer substrate. Two types of NPP industriallyrelevant
cable jacket materials, ethylene propylene
rubber (EPR) and cross-linked polyolefin (XLPO),
were studied in this research. Accelerated thermal
aging was conducted on EPR and XLPO jacket
materials by heating them for various durations up
to 15 weeks (2520 h), at 408 K (135 °C). Thermal
analysis of aged samples reveals degradation of
both cable jackets by the decrease of polymer
weight and crystalline regions. Scanning electron
microscopy and energy dispersive spectrometry
identified the dispersion and constituents of
inorganic additives in the jacket materials. A large
decrease of elongation at break (EAB) of aged
samples as a function of increasing aging duration,
observed by tensile testing, provided an effective
benchmark against which to evaluate the effectiveness
of the capacitive sensor. The capacitance of
the sensor in contact with the samples was
measured and correlated with EAB as a function of
aging time. Values of sensor capacitance measured
at 1 kHz correlated well (correlation magnitude
~0.85) with EAB of the tested materials.
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