Abstract
Lithium is one of the main materials of fuel carrier salt in molten salt reactors. Its neutron cross section provides an important basic datum for physical design of molten salt reactor core and for evaluating the safety of the core during operation. The total neutron cross sections of natural lithium samples with thickness values of 8.00 mm and 15.0 mm are measured, respectively, in an energy range from 0.4 eV to 20 MeV by using a neutron total cross section spectrometer (NTOX) with the transmission method at the Back-n white neutron source of China Spallation Neutron Source (CSNS Back-n) with a 76.0 m time-of-flight path. High quality experimental data are obtained, especially in the energy region of keV and below, which supply a significative supplement of the data, thereby providing more abundant and reliable experimental data for nuclear data evaluation of lithium. Additionally, a theoretical analysis is carried out under the guidance of 1/<i>v</i> law and the multilevel R-matrix theory. And the resonance parameters of n+<sup>6,7</sup>Li reaction around the energy of 260 keV are extracted from the measured data.
Highlights
Normalized neutron energy spectrum measured by the fission chamber
在此基础上, 分别采用 1/v 律 和 R 矩阵理论对 0.1 MeV 以下能区和 0.4—1 MeV 能区的实验数据进行了理论分析, 结果与实验数据 符合, 并获得了 7Li 和 6Li 在 260 keV 附近的中子 共振参数
Summary
本工作基于中国散裂中子源反角白光中子束线 (CSNS Back-n) 飞行时间谱仪, 利用中子全截面测量谱仪 (NTOX), 采用透射法测量了天然锂中子全截面. 在此基础上, 采用 1/v 律和 R 矩阵理论对 MeV 以下能区的新测量数据进行了理论分析, 获得 了 7Li 和 6Li 在 260 keV 能量附近的中子共振参数. 本工作基于中国散裂中子源反角白光中子束 线 (CSNS Back-n)[9−12], 利用中子全截面测量谱仪 (NTOX)[13], 使用透射法在较宽的中子能量范 围内测量了天然锂中子全截面. 在实验数据基础 上, 对 0.1 MeV 以下能区和 260 keV 能量附近的 共振反应分别采用 1/v 律和 R 矩阵理论进行了理 论分析. 式中 Ei 为中子能量, 其中下标 i 表示第 i 个能群; T(Ei) 为中子透射率; NI(Ei) 和 NO(Ei) 为有靶、空
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