Light Water Reactor Sustainability Program Potential to Extend the Range of Established Online Monitoring Technologies, Such as Guided Waves in Nuclear Power Plant Systems

Abstract

The Light Water Reactor Sustainability Program was initiated to evaluate technologies that could be used to perform online monitoring of piping and other secondary system structural components in commercial NPPs. These online monitoring systems have the potential to identify when a more detailed inspection is needed using real-time measurements, rather than at a pre-determined inspection interval.This transition to condition-based, risk-informed automated maintenance will contribute to a significant reduction of operations and maintenance costs that account for most nuclear power generation costs.This report describes the current state of research related to ultrasonic-guided wave testing and its application to defect detection in commercial nuclear power plants. The report analyzes the applicability of the guided wave technology to secondary piping systems, as well as studying the potential for expanding the range of guided wave technology to include bent piping and other piping components. The ultrasonic-guided waves can inspect long stretches of straight piping; however, more complex geometries such as elbows, welds, and tees are causing spurious reflections and coherent noise, which significantly decreases the sensitivity of the technique.The report also analyzes two approaches to suppress coherent noise in guided wave systems: (1) advanced signal processing and pattern recognition based on independent component analysis, and (2) blind source separation and a hardware-based technique using piezoelectric paint, which can be used to facilitate the propagation of mechanical stress waves through piping. It is demonstrated on simulated guided wave data that the independent component analysis is capable of separating different coherent noise components and segregating them from useful signal. The piezoelectric paint approach seems to be a viable alternative to signal processing methods; however, it requires significantly more complicated logistics and initial financial outlay.The future efforts will be concentrated on applying the independent component analysis to real-world guided wave data recorded by the guided wave monitoring system installed on the shell of the lowpressure feedwater heater 13A at Exelon Corporation's Braidwood Nuclear Generating Station. Also, the joint EPRI-INL research efforts will focus on experimental evaluation of piezoelectric paint as a technique to extend the range of guided wave technology. v SUMMARY This report describes the technical potential to extend the range of ultrasonic-guided wave testing in nuclear power plants (NPPs), which is being conducted under the U.S. Department of Energy's (DOE's) Light Water Reactor Sustainability (LWRS) Program. The LWRS Program, funded by DOE's Office of Nuclear Energy, aims to provide scientific, engineering, and technological foundations for extending the life of operating light water reactors (LWRs). This program involves several goals, one of which is ensuring the safe operation of the passive components in NPPs, such as concrete, piping, ste...