Development of High Temperature Electro-Magnetic Acoustic Transducer for In-Service Inspection of Reactor Vessel in Sodium-cooled Fast Reactor

The reactor vessel in a sodium-cooled fast reactor, a generation-IV reactor, is in a high-temperature condition (approximately 200 degrees C) even during the in-service inspection period and the liquid couplant, which is necessary for contact ultrasonic examination, is not permitted to be applied for the inspection to prevent sodium-water reaction. Moreover, the remotely operated vehicle should be employed for inspection in the narrow gap between the reactor vessel and the containment vessel. For the in-service inspection of the reactor vessel under such harsh conditions, a high-temperature electro-magnetic acoustic transducer installable in the remotely operated vehicle was developed in this study. First, the radiation pattern and the signal-to-noise ratio according to the lift-off variation were investigated to analyze the characteristics of the developed transducer. Furthermore, the detectability, heat resistance, and durability of the developed transducer were then evaluated to demonstrate its applicability.