In-situ quantification of dispersity and sphericity of uranyl nitrate sol droplets using holographic imaging

Abstract

Uniform-sized and highly spherical nuclear fuel microspheres are pivotal components in high-temperature gas-cooled reactors. In the manufacturing process of microspheres through external gelation, monodispersed droplets with high sphericity at the dispersion stage establishes the fundamental basis for the subsequent production of superior-quality microspheres. Addressing the monitoring requirements for droplet size and sphericity in dispersion process, this study develops a measurement apparatus based on digital in-line holography. The apparatus records droplet holograms within distances ranging from 96 mm to 183 mm, achieving imaging resolutions between 64 lp/mm to 32 lp/mm. Droplet measurements are conducted for nine operational conditions encompassing varied excitation frequencies and liquid flow rates. Observation under various dispersion parameters reveals diverse droplet morphologies. Polydisperse conditions manifest an abundance of satellite droplets, agglomerated droplets, coalesced droplets, and deformed droplets. The statistical results indicate that at 100 Hz, monodisperse droplets with high sphericity are produced, exhibiting a standard deviation below 30 μm. Moreover, droplet sizes demonstrate a deviation from theoretical calculations within 2.5%. Additionally, preliminary measurements are conducted during the dispersion process of a six-nozzle head, confirming the accuracy on locating droplets of the holographic system within a depth range of more than 30 mm.