Ultrasonic detection of radiolysis bubbles generated in bitumen for dose between 6 and 100 kGy

The ARISE project, supported by the National French Research Center (CNRS) and the Nuclear Safety and Radiation Protection Authority (ASNR), began in 2023 to explore the feasibility of innovative ultrasonic methods to detect the appearance and growth of radiolysis bubbles in bituminized waste products (BWPs). More generally, the subject can cover the investigation of any opaque medium. In this communication, we present results on bitumen samples irradiated at the IRMA French facility, as part of the ASNR BOREE experimental platform. The samples were subjected to total absorbed doses of 6, 50 and 100 kGy with dose rates ranging from 155 to 1230 Gy/h. By using the velocity and attenuation of ultrasonic signals at around 500 kHz, combined with Foldy’s model applied to polydisperse bubble clouds and X-Ray microtomography as validation technique, we demonstrate that relevant parameters can be estimated in a non-destructive manner in irradiated bitumen, namely: the void fraction, bubble radius and the polydispersity of the bubble size distribution. These results pave the way for non-destructive real time monitoring of bubble formation and growth under gamma irradiation in bitumen, as a part of the next phases of this extensive research program.