Fabrication of CeO₂ microspheres by internal gelation process using flow‐focusing droplet generator

Abstract

Sphere‐pac fuel is an alternative nuclear fuel technology in which microspheres of two or more sizes are utilized to fill the cladding tube in place of the more conventional single‐size fuel pellets. This provides leeway for adjusting the fuel pellet packing density and resulting cladding tube porosity. The current investigation makes use of a flow‐focusing droplet generator made from stainless steel (S.S.) 316 L, with a channel internal diameter (I.D.) of 0.5, 0.8, 1, and 3 mm. These microspheres were supposed to be of actinide oxide but here, cerium has been chosen as a surrogate of plutonium. Detailed information about the flow‐focusing droplet generator, internal gelation process, and sphere‐pac fuel has been provided. The size and size distribution of ceria microspheres were investigated by varying the flow rates of the continuous and dispersed phase. The characterization of ceria microspheres has been conducted using techniques such as scanning electron microscope (SEM), X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analyses. The size of prepared monodisperse microspheres was controlled precisely (within ±2%) in the range of 498–2888 μm using four S.S. 316 L flow‐focusing droplet generators with channel I.D. 0.5, 0.8, 1, and 3 mm, respectively, and the coefficient of variation of the size distribution was found to be less than 2%.