本文提出了一种新的延时累加算法。基于底层的JCOGIN(J combinatorial geometry Monte Carlo transport infrastructure)框架和新的延时累加算法,通用型Monte Carlo中子-光子输运模拟软件JMCT的计数能力得到了较大提高。对所考察的非重复结构的单层几何模型问题,JMCT的计数效率较MCNP 4C程序所采用的list scoring技巧高约28%;对于较复杂的重复结构几何模型问题,JMCT的大规模精细计数效率比MCNP 4C高约两个量级。JMCT目前的计数能力为反应堆物理分析及多燃耗步计算奠定了良好的基础。
使用JMCT(J Monte Carlo Transport Code)对来自MIT的全堆芯pin-by-pin精细建模的国际基准模型BEAVRS的热零功率(HZP)状态进行了模拟计算,并与测试数据进行了对比和分析.比较的物理量包括临界本征值、控制棒价值、反应性温度系数、轴向积分的全堆探测器测量值和不同位置四个组件轴向相对功率密度分布.HZP状态下不同控制棒位置插入和硼浓度的临界本征值计算,JMCT结果与理论值1.000的误差小于0.2%,控制棒价值计算结果与测量值符合.JMCT对轴向积分的探测器径向相对功率分布和四个组件的轴向归一化的探测器的计算结果与测量值进行了比较和分析,计算结果与测量值一致,同时清晰地展示了模型增加格架后,轴向功率曲线在相应位置出现下凹的现象.此外,JMCT给出了轴向积分的组件径向相对功率密度分布和轴向相对功率最大处(Z轴位置)的pin径向相对功率密度分布,并与国际知名程序MC21结果进行了对比,两个图像都符合得非常好.随着计算机与并行计算的高速发展,蒙特卡罗程序开始从传统的反应堆校验工具向反应堆设计工具转变.
In this paper, we introduce a multi-material arbitrary Lagrangian and Eulerian method for the hydrodynamic radiative multi-group diffusion model in 2D cylindrical coordinates. The basic idea in the construction of the method is the following： In the Lagrangian step, a closure model of radiation-hydrodynamics is used to give the states of equations for materials in mixed cells. In the mesh rezoning step, we couple the rezoning principle with the Lagrangian interface tracking method and an Eulerian interface capturing scheme to compute interfaces sharply according to their deformation and to keep cells in good geometric quality. In the interface reconstruction step, a dual-material Moment-of-Fluid method is introduced to obtain the unique interface in mixed ceils. In the remapping step, a conservative remapping algorithm of conserved quantities is presented. A munber of numerical tests are carried out and the numerical results show that the new method can simulate instabilities in complex fluid field under large deformation, and are accurate and robust.
