Development of the Under Sodium Viewer (USV); Acoustic propagation characteristics of thin plate structures

Abe, Yuta ; Aizawa, Kosuke ; Komatsu, Kaito*; Kurihara, Akikazu 

The Under Sodium Viewer (USV) has been developed to facilitate visual inspection of internal structures within the reactor vessel of a sodium-cooled fast reactor. The USV utilizes an optical-type ultrasonic receiving sensor that detects the vibrational displacement of a diaphragm-significantly thinner than the ultrasonic wavelength-using laser light. Since the acoustic transmission properties of the diaphragm were not yet fully comprehended, this study experimentally investigated the acoustic transmission characteristics of thin plate structures in water. The findings suggested that, to achieve high image visibility, it may be desirable to minimize waveform damping by designing the diaphragm thickness to be less than 0.25 times the ultrasonic wavelength.