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本文研究了中子扩散计算中空间网格对有效增殖系数、控制棒价值、通量及功率分布的影响。利用扰动理论可以解析地求出,由于空间网格数目有限给有效增殖系数带来的误差正比于网格尺寸的平方。数值结果表明:单群、均匀裸堆近似公式可给出满意的结果。基于此,得到了修正三维计算结果的简单方法。理论分析和数值结果表明:有效增殖系数的网格修正因子几乎与能群数目无关,因此,来自少群计算的修正因子可用来修正多群计算的结果。文中还给出了某些参考状态下的有效增殖系数的两维、三维修正因子以及控制棒价值、通量及功率分布的误差。
In this paper, we study the effect of space grid on effective multiplication coefficient, control rod value, flux and power distribution in neutron diffusion calculation. The perturbation theory can be used analytically to find out that due to the limited number of spatial grids, the error caused by the effective multiplication coefficient is proportional to the square of the grid size. The numerical results show that the single group, uniform nudity approximate formula can give satisfactory results. Based on this, a simple method to correct the three-dimensional calculation results is obtained. Theoretical analysis and numerical results show that the grid correction factor of effective multiplication coefficient is almost independent of the number of energy groups. Therefore, the correction factors from the small group calculation can be used to correct the results of multiple group calculations. In the paper, some two-dimensional and three-dimensional correction factors of effective multiplication coefficient and error of control rod’s value, flux and power distribution are also given in some reference states.