Innovative Application of Spray Direct Thermal Decomposition Denitrification Technology in Nuclear Fuel Preparation

 [Background]：The uranium trioxide prepared via fluidized bed denitrification possessed extremely low activity, which was unable to meet the requirements of follow-up production.The high-pressure spray process can produce the high-activity uranium trioxide, which can solve the problems. [Purpose]:This study aims to resolve key technical bottlenecks of the high-pressure spray process, which involve complete process routes, scale-up reactor design, and the variation mechanism of process parameters.[Methods]:Both the process flow and the large-scale reactor were designed.The test platform was built, and experimental was conducted,to research on high-pressure spray preparation of UO₃ from uranyl nitrate solution . The uranium concentration of the feed liquid was 1000 gU·L-1. Natural gas served as the heating raw material.[Results]:When the natural gas flow rate was controlled at 140~200 m3·h-1, the feed flow rate was80~ 120 L·h-1, and the reaction temperature was 440 ℃, the capacity of the reactor was in 100~150 kg·h-1.

The feed pressure, the feed rate and the reaction temperature were studied. When the feed pressure was the range of 0.2–0.28 MPa  the surface area of UO₃ showed an increasing trend. In contrast, as the feed flow rate increased within the range of 80–120 L·h-1 or ,the reaction temperature increased from 437 ℃ to 450 ℃, the surface area exhibited a decreasing trend. [Conclusions]:The high-activity UO₃was successfully produced in the large-scale reactors by the high-pressure spray technology.