基于内维尔插值的不可分辨共振能区多温度截面生成方法研究

Multi-temperature cross section generation method in unresolved resonance energy region based on Neville interpolation

对于具有快中子能谱的核能系统,其共振截面在不可分辨共振能区因受温度效应的影响,无法准确获得该能区内每个能量对应共振峰的截面,在计算不同温度截面时,需考虑采用与可分辨共振能区不同的计算方法。本文在充分调研国内外蒙特卡罗中子输运中的不可分辨共振能区在线核截面生成方法现状基础上,结合了各核素不同温度下概率表的特征,提出使用基于内维尔(Neville)插值的不可分辨共振能区多温度截面生成方法,在保证核截面精度的同时提高了截面生成效率。国际快堆堆芯模型Bigten1及Bigten2等测试结果表明:该方法与基准值的偏差小于10 pcm,证明了方法的准确性与有效性,可用于反应堆多物理耦合计算。

[Background] For a nuclear energy system with fast neutron spectrum, the cross section in unresolved resonance energy region is affected by the temperature effect and changes, hence, it is not possible to accurately obtain the section of each energy corresponding to the resonance peak in the energy region. When calculating the cross sections under various temperatures, the calculation method different from the resolved resonance energy region must be taken. [Purpose] This study aims to propose a novel multi-temperature cross section generation method to improve efficiency with given accuracy. [Methods] Based on the investigation of the status of the worldwide on-the-fly nuclear cross section generation methods for the unresolved resonance energy region in Monte Carlo neutron transport, the Neville interpolation is used for better efficiency according to the cross section features of probability table at different temperatures. This multi-temperature cross section generation method was verified on two publicly available reactor core models. [Results] Performance test results on international fast reactor core models, i.e., Bigtenl and Bigten2, show that the deviation of the method and the reference value is less than 10 pcm, which proves the accuracy and effectiveness of the method. [Conclusion] The accuracy and effectiveness of this proposed method showed its applicability for reactor multi-physical coupling simulation.