ADS新型密集颗粒流靶无约束界面的研究

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. High power spallation target is a core part of ADS. Compared to the traditional solid target and liquid target, the gravity-driven dense granular-flow target combines the advantages of both, and is a suitable candidate as a high-power spallation target for ADS. In the design of dense granular flow target, below the beam pipe, the granular flow forms a free surface. The stability of the surface is good in preliminary simulations and experiments. This project focus on the free surface and study about the shape and formation of the surface, velocity field and distribution by using large-scale numerical simulation method. Finally, the mechanism of the stability of the surface is studied by combining with micromechanics and the theory of continuous medium.

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核产生散裂中子作为外源中子，驱动和维持次临界堆运行。该系统具有固有安全性，既可实现核废料的最少化处置，同时还有能量输出，被公认为核废料处理的最有效手段。高功率散裂靶是ADS系统的核心组成部分，相比于传统的固态靶和液态靶，新型的重力驱动密集颗粒流靶结合了两者的优点，作为一种高功率散裂靶的可选方案，具有良好发展前景。在ADS新型密集颗粒流靶的设计中，颗粒流动会在束流管道出口下方形成一个无约束界面，在初步的工程预研和数值模拟中，这一无约束界面的稳定性是较高的。本课题拟采用数值模拟的方法，研究颗粒流无约束界面的形状特点和形成规律，速度场及分布。最后结合模拟结果、连续介质理论和颗粒微观力学，揭示无约束界面稳定性的物理机制。

本项目通过数值模拟结合实验的方法，系统研究了ADS密集颗粒流靶中束流管道下方无约束界面的形状、速度场和立场、稳定性以及插入物位置对于流量的影响。同时也研究了束流能量沉积带来的材料膨胀对于这一界面的影响。发展了在大规模离散元模拟程序中对于该界面的统计方法。为ADS密集颗粒流靶中几何构型的优化以及无约束界面的控制提供了物理支持。