ELECTRICAL BREAKDOWN STRENGTH AND AC WITHSTAND IN HARVESTED EPR INSULATIONS FOR NUCLEAR POWER PLANTS
While the operating voltages for some instrument and control (I&C) cables can be greater than 4 kV to operate pumps, controls, and provide auxiliary power, the operating voltage for most I&C cables is near 600 V. Although the electrical stress is not nearly as high in the insulation of these cables, an ac withstand two and one-half times greater than the operating voltage after a simulated design basis exposure (DBE) has been used in environmental qualification (EQ) to determine the ability of an insulation to meet a 40-year lifetime at an operating voltage. While multiple cable lengths greater than 10 feet are needed to replicate this EQ, systematic measurement of the electrical insulation strength in harvested cable insulations can be beneficial to better understand the remaining useful life of the insulation. This understanding can only be realized through systematic comparison to some level of DBE, and electrical insulation strength measurement can provide a baseline for comparison with other mechanical, chemical, and electrical characterizations that have been utilized. Accelerated aging of two types of ethylene propylene rubber (EPR) insulations from harvested cables was carried out, and the electrical breakdown strength and indenter modulus for both insulations were determined. Results showed that degradation of electrical breakdown strength occurred in only one type of BIW insulation and that this degradation did track with that measured by indenter modulus. The methodology for using Weibull statistics for electrical breakdown strength relative to time to failure is discussed.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1607164
- Resource Relation:
- Conference: 19th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors (EnvDeg 2019) - Boston, Massachusetts, United States of America - 4/18/2019 8:00:00 AM-8/22/2019 4:00:00 AM
- Country of Publication:
- United States
- Language:
- English
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