Abstract The aim of this study is to analyze the effect of radial void fraction distribution, considered at three degrees of fidelity, on lattice k ∞ and 2-group homogenized cross sections. The novelty of this work lies in its use of experimentally-determined radial void fraction distributions which allows for fine-scale coolant density data with no predictive uncertainty and which could be prohibitively expensive to simulate over the range of operational parameters used in the experiments. The experimentally-determined radial void fraction distributions are also characterized using a statistical tool called a semi-variogram in order to determine the scale of continuity. Void fraction distributions are averaged at the lattice and subchannel level for comparison with the fine-scale model. Models averaged at the subchannel and lattice level show a difference in k ∞ about 68% of the time. Also, by comparing 2-group homogenized cross-sections, the differences between the subchannel and homogeneous cases are measurable.

中文翻译：

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一种分析径向空隙率分布对 BWR 中子晶格参数影响的多尺度方法

摘要 本研究的目的是分析径向空隙率分布在三个保真度下对晶格 k ∞ 和 2 组均匀截面的影响。这项工作的新颖之处在于它使用了实验确定的径向空隙率分布，这允许在没有预测不确定性的情况下获得精细的冷却剂密度数据，并且在实验中使用的操作参数范围内进行模拟可能非常昂贵。实验确定的径向空隙率分布也使用称为半变异函数的统计工具进行表征，以确定连续性的尺度。空隙率分布在晶格和子通道级别进行平均，以便与精细模型进行比较。在子通道和晶格级别平均的模型在大约 68% 的时间显示 k ∞ 的差异。此外，通过比较 2 组均质横截面，子通道和均质情况之间的差异是可测量的。