Automated ultrasonic scanning of flat plate nuclear fuel

Flat plate nuclear fuel is subject to at least two fabrication induced flaws which lend themselves to ultrasonic detection. This paper describes a production inspection system designed at the INEL that combines separate ultrasonic immersion techniques to detect thin cladding and bonding of fuel to cladding. Clad thickness refers to the amount of aluminum cladding remaining over the fuel after hot rolling, while bonding refers to the quality of bond between the fuel and its aluminum matrix or cladding. The cladding thickness measurement uses a unique 50 MHz transducer operating in pulse-echo mode to detect interfaces as close together as 0.15 mm in aluminum. The transducer is held to within +- 0.1 mm of a given position during high speed scanning by an electro-mechanical servo. The bonding measurement uses two transducers in a thru transmission configuration. A lack of bonding causes a significant loss of signal which is recognized as a flaw. The entire system is configured for maximum through-put on the production line