氟化挥发流化床反应器设计及试验研究

Design and Experimental Investigation of Fluoride Volatility Fluidized Bed Reactor

  • 摘要: 氟化挥发流程作为较有希望实现工业化的干法后处理路线之一,因其对金属、氮化物及氧化物燃料的广泛适用性而备受关注。为开发可支撑乏燃料干法后处理氟化挥发技术的新型反应器原型与工艺参数体系,本研究聚焦乏燃料流态化氟化工艺,基于流化颗粒临界流化速度(0.041 3 m/s),完成了反应器结构参数计算与关键部件设计,成功研制了小型化纯镍流化床装置,并系统开展了温度场分布及颗粒流化行为表征。实验结果表明,反应器核心区可稳定维持650 ℃高温,流态化曲线与温度场数据证实了高温工况下床层的动态稳定性。进一步以UF4为原料进行氟化验证,结果显示,在温度550 ℃、氟气流量20 L/min、投料量100 g条件下,2 h内实现99.4%的UF6转化率,证实了反应器设计的合理性和流化氟化工艺的可行性。

     

    Abstract: China’s nuclear energy development is implemented through a three-step strategy of pressurized water reactor-fast reactor-fusion reactor, accompanied by closed nuclear fuel cycle technology. The high burnup spent fuel from fast reactor generates intense radioactivity, creating technical barriers for conventional aqueous reprocessing. Dry reprocessing technology must be urgently developed to achieve closed fuel cycles. In order to develope a novel fluidized bed reactor prototype and process parameter system for high-temperature fluorination reactor design and process control system, the fluorination-volatilization dry reprocessing was focused, a carrier-material collaborative fluidization mode was proposed based on spent fuel fluorination-volatilization characteristics, alumina particles (280 μm) were selected as fluidization carriers to ensure material stability. Operational gas velocity was determined by combining theoretical critical fluidization velocity (0.041 3 m/s) with fluidization dynamics calculations, enabling structural optimization of the reactor. An integrated filtration-quenching device was designed with a bend-tube pre-distributor + 3 mm nickel ball-packed distribution plate configuration and automatic sealing system to ensure long-term reliability. Temperature field distribution and particle fluidization behavior were systematically analyzed through experiments and numerical simulations. Fluorination tests using UF4 simulated materials were conducted to acquire critical process parameters. The experimental results demonstrate that the reactor core stably maintains 650 ℃ under continuous operation. Characteristic fluidization curves confirm dynamic bed stability in high-temperature environments. During fluorination tests at temperature of 550 ℃ with fluorine gas flow of 20 L/min and 100 g UF4 feed, a 99.4% UF6 conversion rate is achieved within 2 h. These data validate the feasibility of the fluidized fluorination technical route. In summary, a prototype fluidized bed reactor system suitable for dry reprocessing of fast reactor spent fuel is successfully established. The design parameters and operating conditions are demonstrated to effectively support high-efficiency fluorination reactions at elevated temperatures, providing technical foundations for engineering applications. Subsequent studies should prioritize authentic spent fuel verification and long-term operational stability tests to accelerate industrial implementation of fluorination-volatilization technology.

     

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