ABSTRACT

An adaptive setting method of background cross sections is implemented to FRENDY/MG, which is a multi-group neutron cross section generation module, for accurate interpolation of self-shielding factors with a minimum number of background cross sections. Since the dependence of self-shielding factors on background cross section is significantly different among energy group, reaction type, and nuclide, appropriate setting of background cross sections usually requires considerable works. In the present adaptive setting method, the range of background cross section is initially divided into 10 equal intervals and unnecessary background cross section points are eliminated. Then interpolation accuracy at each interval is tested. If the interpolation accuracy in an interval is not sufficient, the interval is successively halved until sufficient interpolation accuracy is obtained. For accurate interpolation of self-shielding factor or reaction rates, the monotone cubic interpolation is used. Verification calculations are carried out for all isotopes in JENDL-4.0. Calculation results indicate that the present method provides an appropriate set of background cross sections while satisfying input error tolerance for self-shielding factors or reaction rates. Typical numbers of background cross sections are from 10 to 25 when the monotone cubic interpolation and error tolerance of 0.01 for self-shielding factors are used.

摘要

多组中子截面生成模块FRENDY/MG实现了背景截面的自适应设置方法，以最小的背景截面数精确插值自屏蔽因子。由于自屏蔽因子对背景截面的依赖性在能量组、反应类型和核素之间存在显着差异，因此背景截面的适当设置通常需要大量工作。在本自适应设置方法中，首先将背景横截面的范围划分为10个等间隔，去除不需要的背景横截面点。然后测试每个间隔的插值精度。如果一个区间内的插值精度不够，间隔连续减半，直到获得足够的插值精度。对于自屏蔽因子或反应速率的精确插值，使用单调三次插值。对 JENDL-4.0 中的所有同位素进行验证计算。计算结果表明，本方法提供了一组适当的背景横截面，同时满足自屏蔽因子或反应速率的输入误差容限。当使用单调三次插值和 0.01 的自屏蔽因子误差容限时，背景横截面的典型数量为 10 到 25。计算结果表明，本方法提供了一组适当的背景横截面，同时满足自屏蔽因子或反应速率的输入误差容限。当使用单调三次插值和 0.01 的自屏蔽因子误差容限时，背景横截面的典型数量为 10 到 25。计算结果表明，本方法提供了一组适当的背景横截面，同时满足自屏蔽因子或反应速率的输入误差容限。当使用单调三次插值和 0.01 的自屏蔽因子误差容限时，背景横截面的典型数量为 10 到 25。