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首页> 外文期刊>Jorunal of computational and theoretical transport >The Asymptotic Drift-Diffusion Limit of Thermal Neutrons
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The Asymptotic Drift-Diffusion Limit of Thermal Neutrons

机译:热中子的渐近漂移扩散极限

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摘要

It is well known that in an infinite, source-free, purely scattering medium with physically realizable cross sections, neutrons attain a Maxwell-Boltzmann distribution characterized by the material temperature. In this work we look at how small variations to these conditions change the behavior of the thermal-neutron distribution in space and energy. Specifically, our analysis examines the influence of small amounts of absorption and a small source as well as temperature variations in the material. We restrict our study to regions away from boundary and initial layers. The result of the asymptotic analysis is that the amplitude of the neutron scalar flux satisfies a drift-diffusion equation in which the diffusion coefficient and drift velocity depend on the first-order anisotropy of the scattering kernel as well as the gradient of the material temperature. Additionally, through first order in the asymptotic expansion the neutron energy distribution is Maxwell-Boltzmann at the local material temperature.
机译:众所周知,在具有可物理实现的横截面的无限,无源,纯散射的介质中,中子达到了以材料温度为特征的麦克斯韦-波尔兹曼分布。在这项工作中,我们研究了这些条件的微小变化如何改变空间和能量中热中子分布的行为。具体来说,我们的分析检查了少量吸收和少量源的影响以及材料中的温度变化。我们将研究限制在远离边界层和初始层的区域。渐近分析的结果是,中子标量通量的振幅满足漂移-扩散方程,其中扩散系数和漂移速度取决于散射核的一阶各向异性以及材料温度的梯度。此外,通过渐进扩展的一阶,中子能量分布在局部材料温度下为麦克斯韦-玻耳兹曼。

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