Analysis of Emerging NDE Techniques: Methods for Evaluating and Implementing Continuous Online Monitoring

There are approximately 440 operating reactors in the global nuclear power plant (NPP) fleet with an average age greater than 20 years and original design lives of 30 or 40 years. The United States is currently implementing license extensions of 20 years on many plants, and consideration is now being given to the concept of “life-beyond-60”, license extension from 60 to 80 years and potentially longer. In almost all countries with NPPs, authorities are looking at some form of license renewal program. In support of NPP license renewal over the past decade, various national and international programs have been initiated. One of the goals of the program for the proactive management of materials degradation (PMMD) is to manage proactively the in-service degradation of metallic components in aging NPPs. As some forms of degradation, such as stress corrosion cracking, are characterized by a long initiation time followed by a rapid growth phase, new inspection or monitoring technologies may be required. New nondestructive evaluation (NDE) techniques that may be needed include techniques to find stress corrosion cracking (SCC) precursors, on-line monitoring techniques to detect cracks as they initiate and grow, as well as advances in NDE technologies. This paper reports on the first part of the development of a methodology to determine the effectiveness of these emerging NDE techniques for managing metallic degradation. This methodology will draw from experience derived from evaluating techniques that have “emerged” in the past. The methodology will follow five stages: a definition of inspection parameters, a technical evaluation, laboratory testing, round robin testing, and the design of a performance demonstration program. This methodology will document the path taken for previous techniques and set a standardized course for future NDE techniques. This paper then applies the expert review section of the methodology to the acoustic emission technique to evaluate the use of acoustic emission in performing continuous online monitoring of reactor components.