The theory and method of the pulsed neutron source (PNS) method measuring the prompt neutron decay constant α₀ of a subcritical system was introduced. Using the Monte Carlo code JMCT, the neutron transport process in a Godiva-like subcritical facility was simulated. The α₀ value of the facility was obtained with PNS method, and was compared with the α-k power iteration result. To investigate the factors affecting the calculated α₀ value of the PNS method, the system response, the fitting residual distributions, and the neutron energy spectra of different time intervals were analyzed. It is observed that the statistical fluctuation is the key factor leading to the inaccuracy of the α₀ calculation value of the facility. Furthermore, to obtain an effective α₀ value with the PNS method, the reasonable width of fitting time window was discussed by analyzing the relationship of the calculated α₀ values and the fitting time width in this paper.

脉冲中子源（PNS）方法测量瞬发中子衰减常数的理论和方法α ₀亚临界系统的引入。使用蒙特卡罗代码JMCT，模拟了Godiva类亚临界设施中的中子传输过程。所述α ₀用PNS方法得到的设施的值，并用所比较的α - ķ功率迭代结果。为了研究影响计算的因素α ₀分析了PNS方法的数值，系统响应，拟合残差分布以及不同时间间隔的中子能谱。据观察，统计波动导致的不精确性的关键因素α ₀的设施的计算值。此外，为了获得有效的α ₀与PNS方法值，拟合时间窗口的合理宽度通过分析的关系讨论的计算的α ₀值，并在本文所述嵌合时间宽度。