Magnetostrictive Guided-wave Transducers for Nuclear Reactor Piping System Monitoring

A 2016 report revealed that 80% of operational nuclear power plants in the U.S. faced financial difficulties or early retirement, mainly because their maintenance costs are 3-4 times higher than those of coal or natural gas plants. The piping systems of nuclear reactors are particularly prone to wear and degradation from environmental stressors, necessitating prompt maintenance. Guided-wave structural health monitoring (SHM) offers a solution by enabling continuous, autonomous pipe monitoring, shifting maintenance from scheduled to condition-based approaches and thereby reducing costs. However, existing SHM systems, which typically use electromagnetic or piezoceramic ultrasonic transducers (UTs), struggle with low signal-to-noise ratios, complex installation, and performance degradation under harsh conditions. Magnetostrictive materials deform in a magnetic field and exhibit magnetization variation when subjected to mechanical stress, leading to innovative UTs. Magnetostrictive iron-gallium alloys (Galfenol) are particularly promising because of their hightemperature and radiation resistance, mechanical durability, and energy conversion efficiency comparable to piezoceramics. Yet, deploying Galfenol UTs in nuclear reactors faces key challenges: (1) Current UT installation relies on deteriorative adhesives; (2) Comprehensive and user-friendly SHM systems accessible to non-experts are lacking; (3) The performance of these systems under hightemperature and radiation conditions remains largely unreported. To address these challenges, this project seeks to develop a groundbreaking Galfenol-based SHM system tailored for in-pile applications. Our multidisciplinary team is dedicated to three core objectives: (1) Simplify sensor integration by directly printing Galfenol on stainless steel host structures. We expect to deliver innovative Galfenol nanomaterial inks, precise printing procedures, and optimized post-processing techniques for effective direct ink writing of Galfenol. This will deepen our understanding of the process-structure-property relationship in printed Galfenol, thereby accelerating its adoption in nuclear applications. (2) Develop a comprehensive SHM system incorporating printed Galfenol UTs, wired data transmission circuits, and a user-friendly graphic user interface. Using multiphysics finite element modeling and laser vibrometry, we expect to deliver computer-aided design tools and advanced signal processing techniques for Galfenol SHM systems. (3) Validate system in extreme conditions at the research reactor at the Ohio State University, simulating conditions equivalent to 70 years of operation in commercial light water reactors. We expect to deliver new insights into how extreme environments impact Galfenol properties, Galfenol-substrate interface strength, and overall performance of Galfenol UTs. The successful completion of this project will lead to enhanced damage prognosis capabilities, reduced operational costs, and improved safety in existing light water reactors. Additionally, this innovative technology holds promise for application in a variety of structures, including heat exchangers and reactor pressure vessels, and is adaptable to a wide range of advanced reactor designs, such as sodium or salt-cooled reactors and high-temperature gas reactors.