加速器驱动次临界系统（ADS）具有优良的次临界安全性、强大的嬗变能力和良好的中子经济性，被公认为是最有前景的乏燃料嬗变途径和降低深埋储藏风险的最具潜力的工具。散裂靶作为中子源，是加速器和次临界堆的耦合部件。中科院ADS战略先导专项提出了新型流化固体颗粒靶的概念。与常见的固态靶和液态靶相比，颗粒靶的优点包括：热移除快，中子产额高，放射产物少，防热冲击，操作方便等。本课题针对钨颗粒靶，采用自主开发的蒙卡程序GMT，研究随机堆积对颗粒靶中子学的影响。对于计算颗粒数巨大的问题，优化了GMT程序，评估颗粒流的随机堆积模型与等效简化模型的差别，并探索其中的变化趋势。通过本课题的研究，将为新型流化颗粒靶设计提供理论指导，并对颗粒相关食品、医药、冶金和化工等领域产生积极意义。

Accelerator Driven Subcritical System (ADS) is considered to be a promising approach for nuclear waste transmutation. It is a good way to process large amount of radiative waste and reduce the risk of deep burying, for its fine subcritical safety, powerful transmutation ability and good neutron economy. Spallation target station, which is the interface between the accelerator and the subcritical core, is an important neutron source in ADS faculties. Here we propose a new concept for a gravity-driven dense granular flow target in a strategic leading science and technology program. Compared with currently widely used solid and liquid targets, this conceptual design has advantages with regard to heat removal, neutron yield, radiotoxicity reduction, thermal shock protection and convenient operation. Based on self-developed Monte Carlo code GMT, our work will focus on the neutron research in tungsten granular target. For the huge granular number problem in the neutron simulation, random model and simplified model will be studied by the optimizing GMT code. We will evaluate the difference and explore the changing trend. The results of this research will provide theoretical guides for the design of the spallation granular flow target and are helpful for related fields, such as food, medicine, metallurgy and chemical engineering.