球壳型钚部件中子多重性测量点模型修正算法

针对中子多重性测量技术中点模型假设在军控核查情况下存在的局限性,为提高核查可靠度,研究点模型算法在武器级球壳型钚部件测量中的逻辑悖论,提出了点模型修正算法。在点模型算法中引入自发裂变中子和氧化物次生中子的二阶矩及三阶矩修正因子,获取了修正后的点模型公式。利用探测效率和门份额均为1的理想中子多重性探测器,结合蒙特卡罗模拟平台,研究了修正因子与球壳型钚部件质量、泄漏增殖因子的关系,并定量了该关系,提出利用迭代法求解修正后的点模型公式。结合蒙特卡罗方法对修正算法进行了数值验证,与点模型算法结果比较:修正算法能将质量偏差平均值从-4.70%降低至-0.70%,氧化物含量份额偏差平均值从11.45%降低至2.31%。

A correction method for point model equations in neutron multiplicity assay of spherical shell plutonium samples

To decrease the significant assay mass bias of spherical shell plutonium samples in nuclear disarmament verification and increase the confidence of verification results, the failure of assumptions in point model equations was studied. Doubles factorial and triples factorial correction factors for spontaneous fission neutrons and oxide generated neutrons were then introduced into the point model equations. The relationships between the correction factors and the sample mass and multiplication were derived with Monte Carlo calculation, and the corrected equations were solved by an iteration process. The calculation results show that: compared with the point model assay, the corrected point model assay decreases the average assay mass bias from -4.70% to -0.70%, and average assay alpha bias from 11.45% to 2.31%.