Aging assessment of circuit breakers and relays

The aging of circuit breakers and relays is important since these devices provide critical services for safety related systems in nuclear plants. Failures of these devices can cause loss of vital functions as well as creating fire hazards. The aging assessments discussed in this paper were sponsored by the U.S. Nuclear Regulatory Commission's Nuclear Plant Aging Research (NPAR) Program. This research is the Phase II effort in which a test program was initiated to investigate and categorize the aging of circuit breakers and relays. The significant elements of the research consisted of the following: determination of current and advanced Inspection, Surveillance and Condition Monitoring (ISCM) Techniques for circuit breakers and relays; laboratory tests, in which new and aged samples of common circuit breakers and relays were tested using these ISCM techniques; in-situ efforts, in which ISCM techniques were performed on equipment in two nuclear plants, and degradation tests, in which ISCM techniques were performed on purposely degraded samples of circuit breakers and relays