Abstract
The conversion of the high-enriched fuel element of the ILL into a low-enriched fuel element implies the development of new investigation tools to analyze the inter-plate distance of an HPRR spent fuel element. Initially of 1.8 mm, this characteristic is indeed impacted during the reactor life cycle by a swelling phenomenon of the fuel plates. For this reason, a high-frequency ultrasonic device respecting the experimental constraints was developed to be introduced into this inter-plate distance. It integrates two ultrasonic transducers resonating at frequencies around 100 MHz and machined at the end of 1 mm thick, 10 mm width, and 1500 mm length of a steel blade. The emission and the acquisition of the ultrasonic signals are ensured by a dual high-frequency transmitter and receiver board. In the present work, the ultrasonic transducer structure and wave propagation are simulated to analyze the echoes produced along the entire path of the propagation. Then, a series of measurements were performed in the laboratory on two known thickness samples of 1.8 mm and 2 mm to validate the ultrasonic device for the in-situ measurement in the reactor building.