中文摘要：

通过使用GEANT4模拟工具包初步模拟了一种新的主动中子测量铀材料同位素组成的方法。其基本原理是对于铀材料,在同种能量中子入射下2,35U与238U发生诱发裂变与（n,2n）、（n,3n）反应截面不同,从而产生的时间关联符合中子计数也不同,根据测量的符合中子的计数反推其同位素组成。模拟采用了能量分别为2.5 MeV与14 MeV的两种单能中子源,使用理想探测器,观测不同入射能量下产生的时间关联符合中子计数比,根据计数比获取其235U丰度。初步的计算结果表明,该方法有一定的可行性,需要进一步将增殖带来的影响减少,以提高分析精度。

英文摘要：

A new active neutron measurement method to detect uranium isotope composition is simulated through the GEANT4 simulation toolkit.The basic principal is that the reaction cross-section for induced fission,（n,2n） and（n,3n） is different for different isotopes of uranium,resulting in that time-correlated coincidence neutrons are different.According to the coincidence neutrons,the isotope composition of uranium can be reached.The simulation uses two incident neutron energies that are 2.5 MeV,14 MeV.Through the ratio of the two coincidence neutrons detected by ideal detector,the abundance of 235U can be reached.The preliminary simulation result shows that the method is feasible.