蒙特卡罗中子输运宽能区在线核截面生成方法研究

发布时间：2018-11-27 06:54

【摘要】：反应堆堆芯温度变化时,堆内各种材料的中子截面均随温度发生变化,从而引起反应性变化。为了准确模拟反应堆内不同温度下中子与各种材料间的相互作用,需要生成不同温度下的反应截面。传统在线核截面生成方法虽然避免了直接存储大量核截面数据,但是仍然存在严重的效率低下以及能区适应性窄的问题。本文在充分调研国内外蒙特卡罗(简称蒙卡)中子输运中的在线核截面生成方法现状基础上,基于中国科学院核能安全技术研究所·FDS团队自主研发的超级蒙卡核模拟软件系统SuperMC,根据可分辨共振能区、热能区与不可分辨共振能区截面的特点,开展了蒙卡中子输运宽能区在线核截面生成方法研究。本文的主要研究内容与创新点包括:(1)提出了基于双指数变换-高斯积分耦合的可分辨共振能区在线核截面生成方法。针对宽能区中可分辨共振能区截面生成耗时严重问题,提出在低能区使用基于双指数变换的在线核截面生成方法,在高能区使用基于高斯-厄米特积分的在线核截面生成方法,在保证核截面精度的同时,极大地提高了截面生成效率。测试结果显示,该方法在保证核截面生成精度的基础上,与解析方法相比截面生成效率提高达12倍;国际临界安全基准例题Jezebel及Godiva等的验证结果证实了该方法的有效性。(2)提出了基于Neville插值的热能区在线核截面生成方法。根据温度相关的热散射截面特性,提出使用Nevlle插值算法在线生成目标温度对应的热散射截面。采用国际核数据委员会发布的S(α,β)基准例题等进行测试,结果表明,在保证精度同时,使用基于Neville插值的热散射截面在线生成方法比传统方法的效率提高一个数量级以上。(3)发展了基于分段线性插值的不可分辨共振能区在线核截面生成方法。该方法结合了不同温度下概率表参数的特征,使用相邻温度间隔的核截面经分段线性插值方法在线生成目标温度的核截面。国际快堆堆芯模型bigtenl及bigten2等测试结果表明,该方法与基准值的偏差小于20pcm,证明了方法的准确性。为了验证本文提出的宽能区在线核截面生成方法的准确性和有效性,采用国际临界安全基准例题、反应性多普勒系数基准例题与IAEA BN-600基准例题等进行了综合验证。通过与传统核截面生成方法与基准值进行对比,结果表明本文发展的蒙特卡罗中子输运在线核截面生成方法能够准确高效地生成各种温度下的中子截面,可用于反应堆多物理耦合计算。
[Abstract]:When the reactor core temperature changes, the neutron cross section of various materials in the reactor varies with the temperature, which causes the reactivity change. In order to accurately simulate the interaction between neutrons and various materials at different temperatures in the reactor, reaction cross sections at different temperatures should be generated. Although the traditional on-line generation method avoids storing a large number of nuclear cross-section data directly, there are still serious problems such as low efficiency and narrow energy region adaptability. In this paper, based on the investigation of the present situation of on-line nuclear cross section generation in Monte Carlo neutron transport at home and abroad, Based on the characteristics of the super Monka nuclear simulation software system SuperMC, developed by the FDS team of the Institute of Nuclear Safety Technology of the Chinese Academy of Sciences, according to the cross sections of the distinguishable resonance energy region, the thermal energy region and the indistinguishable resonance energy region, In this paper, the method of generation of nuclear cross section in the wide energy region of neutron transport in Monka is studied. The main research contents and innovations in this paper are as follows: (1) an on-line generation method of discernible resonance energy region core cross-section based on double exponential transformation and Gao Si integral coupling is proposed. In order to solve the problem of time-consuming generation of the visible resonance cross section in the wide energy region, an on-line generation method based on double exponential transformation is proposed in the low energy region and an on-line generation method based on Gauss Hermitt integral in the high energy region. At the same time, the accuracy of the core section is guaranteed, and the efficiency of section generation is greatly improved. The test results show that the efficiency of cross section generation is 12 times higher than that of analytical method on the basis of ensuring the generation accuracy of the core section. The validity of the proposed method is verified by Jezebel and Godiva. (2) an on-line generation method of thermal energy region nuclear cross section based on Neville interpolation is proposed. According to the characteristic of the temperature dependent heat scattering cross section, the Nevlle interpolation algorithm is proposed to generate the heat scattering cross section corresponding to the target temperature online. Using the S (伪, 尾) benchmark and other examples issued by the International Nuclear data Commission, the results show that, at the same time, the accuracy is guaranteed, The on-line generation method of heat scattering cross section based on Neville interpolation is more than one order of magnitude higher than that of the traditional method. (3) the method of generation of core cross section in the indiscernible resonance energy region based on piecewise linear interpolation is developed. Based on the characteristics of probability table parameters at different temperatures, the kernel cross-section of the adjacent temperature interval is generated online by piecewise linear interpolation. The test results of bigtenl and bigten2 show that the deviation between the method and the reference value is less than 20pcmwhich proves the accuracy of the method. In order to verify the accuracy and effectiveness of the method proposed in this paper, the international critical safety benchmark, the reactive Doppler coefficient benchmark and the IAEA BN-600 benchmark are used to verify the accuracy and effectiveness of the proposed method. Compared with the conventional nuclear cross section generation method and the reference value, the results show that the Monte Carlo neutron transport on-line nuclear cross section generation method developed in this paper can accurately and efficiently generate neutron cross sections at various temperatures. It can be used for reactor multi-physical coupling calculation.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TL329

【相似文献】