Numerical parametric study of a waveguide-based ultrasonic sensor for telemetry in a sodium-cooled fast reactor

This paper presents a collaborative work that started out under the framework of the Generation IV International Forum regarding ultrasound telemetry in sodium-cooled fast reactors. The liquid sodium environment imposes harsh constraints on immersed transducers for telemetry. An alternative approach consists in locating a transducer outside of the reactor core and exciting guided waves that are conducted by a waveguide inside the liquid sodium from where they radiate inside the reactor and can be used for telemetry and associated inspections. This work presents a numerical method coupling the propagation of elastic guided waves in long waveguides with a liquid environment and applies it to conduct a parametric study on several waveguide designs. The simulated results are compared to data from real waveguides obtained in a water tank, carried out with 9 sensors, in order to cover a large design space and ensure the validity of the modeling approach. Good agreement is observed with respect to the main measured quantities. The limits of the developed model are discussed with the help of these results. In particular, variations linked to untracked experimental parameters are shown to have an impact on results.