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首页> 外文期刊>Annals of nuclear energy >Control rod treatment for FEM based radiation transport methods
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Control rod treatment for FEM based radiation transport methods

机译:基于FEM的辐射传输方法的控制棒处理

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摘要

This paper presents a novel control rod treatment for finite element method (FEM) based reactor physics simulations. The new method falls into the class of homogenization methods which treat material interfaces in mesh elements by defining a representative, homogenized nuclear cross section set. In contrast to existing homogenization based cusping treatments that attempt to approximate flux-volume weighting of the cross sections, we propose to exactly integrate terms appearing in the variational form of the transport or diffusion equation over mixed material elements. This goal is achieved by defining smoothly varying cross sections in elements that straddle material boundaries. It is shown that the smoothly varying cross sections can be obtained by projecting the piecewise set of cross sections onto the set of Legendre polynomials up to a finite order. Implementation of smoothly varying cross sections is supported within the Rattlesnake radiation multiphysics code at the Idaho National Laboratory. Homogenization methods traditionally suffer from cusping effects that originate from overestimation of absorption cross sections in strongly neutron-absorbing materials as found in control rods. We demonstrate that the presented method is (1) highly effective in removing cusping effects and (2) provides accurate results based on the C5G7-TD benchmark, a time-dependent version of the C5G7 benchmark. (C) 2018 The Author(s). Published by Elsevier Ltd.
机译:本文提出了一种基于有限元方法(FEM)的反应堆物理模拟的新型控制棒处理方法。新方法属于均质化方法类别,该方法通过定义代表性的均质化核横截面集来处理网格元素中的材料界面。与现有的基于均质化的尖峰处理(试图对横截面的通量-体积权重进行近似)相反,我们建议对在混合材料元素上以传输或扩散方程的变分形式出现的项进行精确积分。通过在横跨材料边界的元素中定义平滑变化的横截面,可以实现此目标。结果表明,可以通过将分段的分段集合投影到有限数量的Legendre多项式集合上来获得平滑变化的截面。爱达荷州国家实验室的响尾蛇辐射多物理场规则支持平滑地改变横截面的实现。传统上,均质化方法会受到尖峰效应的影响,这是由于对高中子吸收性材料(如控制棒)中的吸收截面的高估所致。我们证明了所提出的方法(1)在消除尖峰效应方面非常有效,并且(2)基于C5G7-TD基准测试(C5G7基准测试的时间依赖性版本)提供了准确的结果。 (C)2018作者。由Elsevier Ltd.发布

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