Power and instrumentation cables play a crucial role in the safe operation of Nuclear Power Plants (NPPs). Thermal and other stressors present in the reactor environment cause the cable materials to degrade. In this work, dielectric and mechanical properties of cable insulation and jacket materials are studied as they are thermally aged, supporting development of non-destructive evaluation sensors for monitoring cable aging. Materials selected for this study are found in certain types of single-core unshielded power cables. These utilize ethylene propylene rubber (EPR)-based insulation material and chlorinated polyethylene (CPE)-based jacket material. Flat mats of these materials were obtained from the cable manufacturer and thermally aged at 140 °C in an air-circulating oven. Elongation-at-break was measured on tensile specimens stamped from the aged mats, and dielectric properties were measured from 100 Hz to 100 kHz using a parallel plate capacitor and precision LCR meter. In the case of aged EPR-based materials, rapid decrease in elongation at break indicating end of useful life was accompanied by a significant increase in dissipation factor, D, measured at 100 kHz. Capacitive measurement of D shows promise, therefore, as a non-destructive indicator of corresponding mechanical property changes in thermally-aged EPR-based insulation materials.
There are over 600 miles of power cable installed in a typical nuclear power plant. Degradation due to thermal and radiation damage of cable insulation has been identified as one of the key factors that contribute to the loss of performance and ultimate failure of the cable. A critical aspect of cable health monitoring is to understand the nature of degradation and develop aging models to predict the service lifetime of the insulation. In this work, it is proposed to evaluate the effectiveness of four different modeling approaches to evaluate the aging behavior and remaining useful life of industrial-grade ethylene propylene rubber (EPR), a cable insulation material used extensively in nuclear power plants. A comparative study of the ability of these prognostic models to reliably predict the service lifetime of EPR while accounting for the presence of various inclusions and impurities in the production grade material will be conducted, to test their industrial applicability and evaluate their relative performance
The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this dissertation. The Graduate College will ensure this dissertation is globally accessible and will not permit alterations after a degree is conferred.
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