贫化铀/聚乙烯球壳交替系统中铀-238中子俘获率的测量与分析

为校验次临界能源堆的概念设计,建立了贫化铀/聚乙烯球壳交替系统, 采用活化法测量²³⁸U的中子俘获率. 贫化铀片置于系统内与入射D离子束成90^o的方向上活化 ,用HPGe探测器测量²³⁸U俘获中子衰变产生的²³⁹Np 衰变产生的277.6 keV特征γ射线计数,实验修正了贫铀片对277.6 keV γ射线的自吸收, 得到了交替系统中²³⁸U (n, γ)反应率的径向分布,反应率的相对不确定度为3.5%-3.7%, 并计算得到系统上整个贫铀区中²³⁸U的总中子俘获率为2.24 ± 0.09. 用MCNP5程序在常用ENDF库下进行了模拟计算, ²³⁸U (n, γ)反应率分布计算与实验一般在5%以内符合, 总俘获率在1%以内符合.

Measurement and analysis of neutron capture rate of U-238 in an alternate depleted uranium/polyethylene system

In order to check the conceptual design of subcritical reactor,an alternate depleted uranium/polyethylene-shell simulation device was established,to carry out uranium-238 neutron capture rate experiment using activation technique.The depleted uranium foils were activated at 90°to the incident.By measuring the 277.6 keV y-ray emitted from ²³⁹Np generated by ²³⁸U（n,γ） ²³⁹U reaction and correcting self-absorption of uranium experimentally,the ²³⁸U（n,y） reaction rate with an uncertainty between 3.5%and 3.7%and a total neutron capture of 2.24±0.09 of the system were obtained.The experiment was simulated using MCNP5 code with ENDF libraries.The simulations and measurements accord within 5%for the ²³⁸U（n,γ） reaction rate and within 1%for the total neutron capture rate of ²³⁸U.