Online Cable Condition Monitoring and Aging Management of Nuclear Power Plant Cables and End Devices.

Currently many nondestructive evaluation techniques exist for cable condition monitoring, but most of these cable analysis methods are applied to de-energized cables and require disconnecting the cable from one or both ends of the circuit. These limitations can allow some cable circuit problems to go undetected for extended periods of time. The ability to monitor critical cable circuits while the plant is operating without disconnecting the cable under test will save the nuclear power industry significant time, cost, and personnel resources while increasing efficiency of maintenance outages. Heat, radiation, and humidity present in nuclear plant environments can cause electrical cable insulation to become brittle, crack, or degrade over time. This degradation creates cable circuit problems that can be intermittent, such as a degraded connector exposed to vibration or thermal cycling. Other degradation methods can be progressive, as with polymer aging in a harsh environment. Loose connections, equipment failure, and environmental degradation reduce the reliability of an entire circuit or control loop. Many cable faults are produced by changes in conditions such as temperature and vibration during normal plant operation that can be very difficult to locate without a continuous monitoring system. Cable failure mechanisms such as these have resulted in unnecessary safety system actuation, loss of indication, spurious alarms, time lost for troubleshooting, and unnecessary component replacement. In response to the nuclear industry’s need for a cable on-line condition monitoring system, a hands- on research and development effort is proposed involving cable circuits that are representative of types used in nuclear power plants. Specifically, reflectometry and other cable condition monitoring test methods will be evaluated for locating faults and quantifying progressive polymer aging degradation for energized, connected cable circuits that can be tested while the plant is operating. The goal of this Phase I project is to demonstrate the feasibility of a continuous cable on-line monitoring system for fault location and trending degradation of energized, in-service nuclear power plant cable circuits, including the cable, connectors, and end devices. This goal will be accomplished by researching both established and innovative reflectometry techniques, as well as other cable testing methods, for suitability of signal injection into energized cable circuits. Laboratory circuits representative of nuclear power plant cable systems will be constructed and the effect of signal injection on circuit operation will be quantified. Finally, a conceptual design will be developed for prototyping in Phase II. The commercialization of the project will focus on developing both a permanently installed and portable on-line cable condition monitoring test system used to provide testing and engineering services to help locate faults and trend aging degradation of critical low voltage and I&C cables while the plant is operating.