Abstract
The future HPRR LEU fuel plates will have to withstand aggressive irradiations leading to a swelling phenomenon. This latter induces structure modifications and impacts the initial inter-plate distance. This distance is investigated, under the access and microscopic resolution constraints, within the PERSEUS Project aiming the development of a non-destructive ultrasonic device. With a thickness of 1 mm to be inserted into the 1.8 mm water channel width of the High flux Reactor (RHF), the device relies upon two ultrasonic transducers connected to an electronic system. It allows time of flight and ultrasonic velocity estimations. The feasibility being already proved, optimizations on components of the measurement chain and signal processing have led to a new device. A developed motorized bench has allowed reproducibility measurements with a 500 nm resolution. Then, a reproducibility devices' radiation resistance experiment, carried out in the Arc-nucleart Institute, demonstrated their parameters stability under 3500 kGray. Experiments were also realized on the RHF fuel element where vertical position, distance and temperature were evaluated, with a 1 µm precision on channel gap thickness. Future works will explore waves ability to be focused in the depth of the plates.