Aging management of instrumentation & control sensors in nuclear power plants

Pressure to improve plant efficiency and maximize safety and the increasing age of existing NPPs are forcing the global nuclear power industry to confront the challenges of aging – caused by stressors such as temperature, humidity, radiation, electricity, and vibration – in key instrument & control (I&C) components like pressure transmitters, temperature sensors, neutron detectors, and cables. Traditional aging management methods, such as equipment replacement, required the process to be shut down. Recent aging management technologies, collectively known as online monitoring (OLM), enable plants to monitor the condition and aging of their installed I&C while the plant is operating. Developed through R&D initiatives worldwide, such OLM techniques include low- and high-frequency methods that use existing sensors, such as noise analysis; methods based on test or diagnostic sensors, such as for vibration-measuring accelerometers; and methods, such as the power interrupt (PI) test, based on active measurements made by injecting a test signal into the component under test. A review of these aging management methods, their effectiveness, and their interrelation provides a foundation for understanding the next stage in the evolution of OLM: truly integrated hybrid OLM systems capable of robust condition monitoring in both novel and familiar operating conditions.