Use of Time-Domain Dielectric Spectroscopy to Evaluate the Lifetime of Nuclear Power Station Cables.

摘要

The use of the dielectric properties of insulation to assess the lifetime of electrical insulation in a nuclear power plant is assessed. The factors governing dielectric constant and loss over an extended frequency range are summarized. The Time-Domain Spectrometer is shown to be suitable for the task, given the changes expected in an insulator upon exposure to radiation and the wide range of lower frequencies that it can cover. Several sets of cable samples of the types expected to be found in a reactor were measured with the Time-Domain Dielectric Spectrometer and the results are reported. It is shown that for the hydrocarbon based insulation studied, with the aging conditions used, a characteristic loss region centered near 10 Hz at 50C is radiation induced and follows dose. The loss seems to be a good marker for radiation exposure and history, even in the presence of large losses due to the presence of filler and other sources of high loss. The use of loss data is proposed as a good possibility for lifetime assessment with further research. Comparison is made with some mechanical measurements that illustrate the enhanced sensitivity of dielectric measurements.