High-Temperature Magnetostrictive Acoustic Emission Transducer for Fuel Pin Burst Detection

In a loss-of-coolant accident, residual decay heat causes a rapid increase in temperature and internal pressure within the fuel pin, leading to plastic deformation and eventual bursting. Acoustic emission (AE) monitoring has been explored as a method of accurately detecting the timing of pin bursts. While most AE transducers are of the piezoelectric type, magnetostrictive materials such as Remendur and Galfenol do offer an alternative and are often better suited for high-temperature and nuclear radiation environments, due to their superior mechanical robustness. This study presents experimental results from burst detection tests performed on stainless-steel pins when using both piezoelectric and magnetostrictive (Fe-Co alloy) AE transducers. The piezoelectric AE sensor was commercially available, whereas the magnetostrictive transducer was developed in-house. During the burst tests, stainless-steel pins were pressurized and placed in a high-temperature furnace. Each pin was subjected to its own separate test. The furnace temperatures were set at 300°C, 400°C, 500°C, and 650°C for these individual tests, and the pins were pressurized until burst. Both types of AE transducers were clamped onto the heat sink surrounding the stainless-steel pins. The results indicate that both the piezoelectric and magnetostrictive AE transducers successfully detected the timing of pin bursts and could cross-verify each other at the furnace test temperatures of 300°C, 400°C, and 500°C. At 650°C, which exceeds the commercial piezoelectric AE sensor's maximum operating temperature of 540°C, only the magnetostrictive AE sensors were used, and these sensors successfully detected the timing of pin bursts at 650°C. These experiments demonstrate the effectiveness of magnetostrictive AE sensors in high-temperature environments.