基于白光中子源的核石墨硼当量测量

核材料中热中子吸收截面高的杂质会引起堆芯反应性的变化，一般用硼当量表示这些杂质对热中子的吸收，硼当量是衡量核材料纯度的重要指标之一。热中子宏观吸收截面法是硼当量测量的方法之一，测量时采用同位素中子源则精度低，而白光中子源产生的中子强度高、方向性好，且可慢化为热谱，能有效提高硼当量测量精度。本文基于15 MeV电子加速器驱动的白光中子源开展核石墨硼当量测量的研究，利用蒙特卡罗模拟并优化实验方案，对实验数据进行检验与修正，建立核石墨硼当量测量定量分析方法。该方法能快速、准确检测核材料的硼当量，对反应堆的物理设计、安全性评估等具有重要意义。

Boron Equivalent Measurement of Nuclear Graphite with Photoneutron Source

Impurities in nuclear materials with high thermal neutron absorption cross section will change the reactivity. The absorption of thermal neutrons by these impurities is represented by boron equivalent, which is one of the important factors to measure the purity of nuclear materials. Boron equivalent can be determined directly via the measurement of macroscopic thermal neutron absorption cross section based on an isotopic neutron source, but with lower accuracy. The photoneutron source, which can generate neutrons with higher intensity, better direction and lower energy, can effectively improve the accuracy of boron equivalence measurement. Therefore, the boron equivalent measurement of nuclear graphite was carried out with the photoneutron source driven by 15 MeV electron LINAC. Monte Carlo simulation method was used to optimize the experimental scheme, and the experimental data were tested and modified. Finally, the quantitative analysis method was established for the measurement of graphite boron equivalent. This method can quickly and accurately measure the boron equivalent of nuclear materials, which is of great significance for the physical design and safety assessment of the reactor.