Abstract The aim of this paper is the analysis of the neutron diffusion coefficient with 3D approximation of the up-scaled neutron diffusion equation. In this work we present comparisons of 3D ordered and disordered approximations. To this end, we compute the effective diffusion and interfacial neutronic flux coefficients in representative cells of fuel elements composed by several TRISO particles randomly collocated. The ensemble of 700 realizations, show more variations in the numerical estimation of the interfacial neutronic flux coefficient than for the effective diffusion coefficient. The assumption of one ordered arrangement of TRISO particles inside the fuel particle is enough for estimation of the diffusion coefficient. A comparison of the upscaled model with effective coefficients computed from disordered arrangements, with analytical solutions for unidirectional neutron diffusion demonstrates that the classical diffusion theory and the Boltzmann equation would yield similar predictions for long times and highly or poorly absorbent materials.

中文翻译：

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球形核燃料中 TRISO 粒子无序排列的中子扩散系数

摘要 本文的目的是用放大的中子扩散方程的 3D 近似分析中子扩散系数。在这项工作中，我们展示了 3D 有序和无序近似的比较。为此，我们计算了由随机配置的几个 TRISO 粒子组成的燃料元件的代表性电池中的有效扩散和界面中子通量系数。与有效扩散系数相比，700 个实现的集合在界面中子通量系数的数值估计中显示出更多的变化。假设燃料颗粒内 TRISO 颗粒的一种有序排列足以估计扩散系数。放大模型与从无序排列计算的有效系数的比较，