An ultrasonic approach to identify in-core reactor fuel for safeguards applications

An ultrasonic fuel assembly identification system is proposed as a means for maintaining continuity of knowledge for safeguarding fuel within a sealed or long-life core of a liquid-metal-cooled reactor. Publicly available concept design information of the LeadCold SEALER reactor is used as an example to exhibit how an ultrasonic system can be used to read a series of notches of various depths, and to subsequently translate them into fuel assembly identification numbers using an encoding scheme. In this work, a number of encoding schemes are considered and evaluated for the maximum number of ultrasonic transducers that can fail and still guarantee recovery of the fuel assembly identification. For some schemes, up to 8 of 12 transducers can fail and still allow the fuel assembly identification to be guaranteed recoverable; up to 13 notch depths per notch are required in some instances. Supporting this assessment, simulation of the ultrasonic read-out system indicates that a notch depth resolution of approximately ∼1 mm is possible at 4.75 MHz. Some discussion is provided concerning practical aspects of deploying such an identification system for the long term in a high-temperature, high-radioactivity reactor environment.