Development of ultrasonic glancing angle imaging methodology for detection of subassembly protrusion in fast breeder reactors

The paper presents an ultrasonic glancing angle imaging based methodology developed for detection of protrusion and mapping of subassembly (SA) heads in a pool type liquid metal cooled fast breeder reactor. In the developed methodology, mapping of SA heads is performed by a single sweep of a transducer inclined at an oblique angle close to the horizontal plane. A large number of SAs is covered simultaneously due to divergence of the ultrasonic beam. A significant increase in the acoustic amplitude corresponding to the protruded SA and reduction in the amplitudes corresponding to the SAs in the shadow region can be used for detection of SA protrusion. Further, decrease in the time of flight of signal corresponding to the protruded SA can be used for quantitative estimation of the extent of SA protrusion. The present study demonstrates in water condition that ultrasonic glancing angle imaging methodology can be used for mapping of SA heads and to detect their protrusion, if any, without the need of placing an ultrasonic transducer just above the targeted SA.