ENDF/B-VIII.β与ENDF/B-VII.1中水的热中子散射截面数据对比分析

Comparison of the Thermal Neutron Scattering Cross Section of Water Based on ENDF/B-VIII.β and ENDF/B-VII.1

以常见的慢化剂材料轻水为例,分析了ENDF/B评价库中两个版本ENDF/B-VIII.β与之前ENDF/BVII.1中热中子散射截面数据的差异。由于ENDF/B-VIII.β与ENDF/B-VII.1等两个版本中热中子散射截面的温度不尽相同,为定量分析同一温度下二者的差异,通过插值方法得到了任意温度下的热中子散射截面数据。对比发现,二者在同一温度下的热中子散射数据存在差异。相对于ENDF/B-VII.1评价库版本而言,基于ENDF/B-VIII.β评价库版本加工得到的束缚在水中的氢的热中子散射截面与ENDF/B-VII.1存在较为明显的差异,两个版本给出的低温情况下的中子与靶核碰撞后的平均散射角余弦在热区的低能段出现极小的负值。此外,当温度高于室温时,在热区的低能段ENDF/B-VIII.β给出的平均次级中子能量要稍大于ENDF/B-VII.1给出平均次级中子能量。

This work takes the traditional moderator material H_2O for example, the differences between ENDF/B-VIII.β and ENDF/B-VII.1 versions from the ENDF/B nuclear evaluated library are analyzed. In order to compare the thermal neutron scattering data between ENDF/B-VIII.β and ENDF/B-VII.1 versions under the same temperature, the interpolation method is used to obtain the thermal neutron scattering data under arbitrary temperatures. There are some differences between ENDF/B-VIII.β and ENDF/B-VII.1 versions, the thermal neutron scattering cross sections of H bound in H_2O within ENDF/B-VIII.β is different with that of ENDF/B-VII.1, the scattering angle cosines of the neutron and target nuclei from the two libraries are slightly smaller than zero in lower energy range within thermal range. Moreover, the second scattering energy spectrum from ENDF/B-VIII.β is slightly harder than that from the ENDF/B-VII.1 in higher energy range within thermal range when the temperature is higher than room temperature.