利用MCNPX模拟研究不同中子源对有源符合中子法的影响

利用MCNPX软件建立了有源井型符合计数器(简称AWCC)测量模型，模拟了诱发中子源分别为Am-Li源和Am-Be源时AWCC测量贫化铀的中子符合计数率，研究了两种诱发中子源下AWCC测量贫化铀质量的精度。研究表明，Am-Be源引起的诱发中子符合计数率低于Am-Li源引起的诱发中子符合计数率，Am-Be源下的质量刻度曲线拟合度高于Am-Li源下的，相应的质量测量误差也小于Am-Li源下的，Am-Li源下的检验点铀质量相对误差区间为0.3%~13%，Am-Be源下的为0.1%~4.5%。使用AWCC装置测量贫化铀质量时，选取Am-Be源作为诱发中子源时相对误差更小。

Study on the Influence of Different Neutron Source on the Active-well Neutron Coincidence Method by MCNPX

The model of Active-Well Coincidence Counter(AWCC) was established by MCNPX, meanwhile, with two types of induced neutron source (Am-Li and Am-Be), the neutron coincidence count rate of low enriched uranium was simulated, and the comparison of the measurement accuracy between the two simulations was also demonstrated. It was found that the coincidence count rate induced by Am-Be source was lower than that induced by Am-Li source, and the fitting degree of scaled mass curve under Am-Be source was better than that under Am-Li source, the corresponding relative error was also lower than that of under Am-Li source. The relative error range of uranium mass corresponding to the inspection point under Am-Li source is 0.3%~13%. The relative error range under Am-Be source is 0.1%~4.5%. According to the results, for the measurement of the mass of low enriched uranium by AWCC, it could be better to choose Am-Be source for reducing measurement relative error.