ADS新型密集颗粒流靶的流量研究

Unlike traditional reactors, in an accelerator driven sub-critical system (ADS), the heavy metal target, bombarded by the high energy and current proton beam generated by the accelerator, serves as a neutron source to drive and sustain the subcritical reactor. This system has an inherent safety, which can achieve the minimum disposal of nuclear waste and output of energy, and is recognized as one of the most effective means for nuclear waste disposal. As a neutron source, high power spallation target is a core part of ADS coupling the accelerator and the subcritical source. A new proposed gravity-driven dense granular-flow target combines the advantages of traditional solid and liquid targets to a large extent, and is a suitable candidate as a high-power spallation target for ADS. The geometry of the granular flow target is a cone hopper with a beam pipe inserted. In preliminary simulations and experiments, it’s found stable flow rate and grain velocity could be obtained. In this project, flow rate and flow type of the target and their constancy and robustness will be studied by simulation and experiment. Their relationship with geometry parameters will be investigated to optimize the geometry design. Finally, the results will be studied by continuum theory and micromechanics to find mechanism of the constancy of the flow rate and the forming of flow types.

不同于传统反应堆系统，加速器驱动次临界系统(ADS)以加速器产生的高能强流质子束轰击重金属靶发生散裂反应提供外源中子来驱动和维持次临界堆运行。该系统安全性优良，其强大的嬗变能力可以在产能的同时实现最少化处置核废料。作为ADS系统的中子源，高功率散裂靶是连接耦合加速器和次临界堆的关键组成部分。在散裂靶设计中，新型的重力驱动密集颗粒流靶很大程度上结合了已有固态、液态靶的优点，具有良好发展前景。ADS颗粒流靶的基本几何构形为中间插入束流管道的锥底漏斗，初步的工程预研和数值模拟表明该构形可以获得稳定的流量以及满足热量输送等需求的流速。本课题拟采用数值模拟实验辅助的方法，在已有相关基础上详细研究颗粒流靶流量、流场流型与靶几何参数的关系以及颗粒靶流动的稳定性、鲁棒性问题，进一步获得可能合适的参数边界以优化设计。同时在理论上，结合模拟实验结果和连续介质理论等，揭示流量稳定以及流型分区的物理机制。

本课题通过对ADS颗粒流靶流量流场等问题的研究，为颗粒流靶靶形参数的设计提供了可行的思路和方法。主要完成的工作有：1. 软件算法平台的扩展与完善，实现了描述分析颗粒物质状态的算法，为满足热工流体力学设计要求，算法实现了束靶耦合与颗粒传热。2. 对颗粒流靶的流型分区进行研究，探索了各个分区的特点、颗粒流靶开口和束流管道几何参数对流型分区的影响，以及相应的对束靶耦合后温升的影响。研究发现流型分区的湍流滞留区是控制颗粒极限温升的关键而慢速密集流区则会决定整体的平均温升。3. 在靶运行中加入堵塞微扰，研究了微扰对靶流动稳定性的影响，发现了受到堵塞微扰后，颗粒流靶会有一个回弹并在束流管道内溅出的现象。4. 采用深度神经网络的方法对平底圆开口漏斗进行了流量拟合尝试，得到较好的拟合效果，为颗粒流靶的流量拟合做出了初步探索。5. 进行了颗粒流靶相关的漏斗流颗粒物理研究，在平底漏斗六中发现了壁面成壳现象，在加格挡阻断的准二维漏斗流实验中发现了格挡对漏斗流流型的影响。6. 最终基于上述研究的经验，我们提出了颗粒流靶参数设计的模式化流程，并在该方法的指导下得到了典型的颗粒流靶参数范围。