Abstract At the Kyoto University Critical Assembly experiments on kinetics parameters are carried out at near-critical configurations, supercritical and subcritical states, in the thermal neutron spectrum made with a highly enriched uranium fuel. The main calculated kinetics parameters, the effective delayed neutron fraction (βeff) and the neutron generation time (Ʌ), are used effectively for the estimation of experimental parameters, and the accuracy of experiments on prompt neutron decay constant (α) and subcriticality (ρ$) in dollar units is attained by the numerical results of βeff and Ʌ. Furthermore, the value of βeff/Ʌ is experimentally deduced with the use of the experimental results of α and ρ$, ranging between 250 and −80 pcm. Thus, the experimentally deduced values of βeff/Ʌ that reveal good accuracy through a comparison with those by the MCNP6.1 calculations with JENDL-4.0 are then taken as an index of Ʌ by introducing an acceptable assumption of βeff at near-critical configurations. From the results of experimental and numerical analyses, the experimental value of βeff/Ʌ is important for the validation of Ʌ since kinetics parameters are successfully obtained from the clean cores of near-critical configurations in the thermal neutron spectrum.

中文翻译：

---

京都大学临界组装高浓缩铀芯中的中子产生时间

摘要 在京都大学临界装置中，在由高浓缩铀燃料制成的热中子谱中，在近临界配置、超临界和亚临界状态下进行了动力学参数实验。主要计算动力学参数，有效延迟中子分数（βeff）和中子产生时间（Ʌ），有效地用于估计实验参数，以及瞬发中子衰变常数（α）和亚临界（ρ）实验的准确性$) 以美元为单位由 βeff 和 Ʌ 的数值结果获得。此外，βeff/Ʌ 的值是使用 α 和 ρ$ 的实验结果通过实验推导出来的，范围在 250 和 -80 pcm 之间。因此，通过在接近临界配置下引入可接受的 βeff 假设，通过与 MCNP6.1 计算和 JENDL-4.0 的比较显示出良好精度的 βeff/Ʌ 的实验推导值被视为 Ʌ 的指数。从实验和数值分析的结果来看，βeff/Ʌ 的实验值对于验证 Ʌ 很重要，因为动力学参数是从热中子谱中近临界构型的清洁核心成功获得的。