离线测量钍快中子裂变反应率方法

钍快中子裂变反应率是钍铀燃料循环中的重要数据.为了测量基于聚变-裂变混合能源堆包层概念设计的钍样品在宏观中子学装置中的钍快中子裂变数据,发展了钍快中子裂变率的离线活化γ测量方法.通过测量232Th裂变碎片85mKr的β衰变产物85Rb发射的151.16 keV特征γ射线,并结合钍裂变产额数据,获得了钍样品装置中232Th裂变反应率的分布.详细介绍了此方法的原理和影响因素,并利用14 MeV的D-T中子源在贫铀球壳中开展了校验实验,实验不确定度为5.3%—5.5%.采用MCNP5程序和ENDF/B-VI及ENDF/B-VII数据库模拟计算的结果与实验结果在实验不确定度内基本符合,这证明该方法能够有效地模拟装置中232Th裂变反应率.

Determination of thorium fission rate by off-line method

Thorium fission reaction rate is an important datum in uranium-thorium fuel cycle. In order to measure the thorium fission rate on the thorium sample equipment which is set up by the conceptual design of the subcritical reactor and to check the thorium data, the off-line activation γ measurement method of thorium fission rate is developed. Combined with thorium fission yield data of ^85mKr, the ²³²Th fission reaction rate distribution in thorium sample device can be obtained by measuring the 151.16 keV feature gamma rays emitted by fission fragment ^85mKr. Details of the principles and factors of this method are discussed, and the verification experiment is carried out on a depleted uranium shell of R13.1/30.0 cm with D-T neutrons. The relative uncertainty of experiment is 5.3%-5.5% for thorium fission reaction rates. The experiment is simulated using MCNP5 with ENDF/B-VI and ENDF/B-VII libraries, simulation results and experimental results accord well with each other within the experimental uncertainty, showing that this approach developed in this paper can work well for determining the thorium fission rate.
Keywords：thoriumfission rateoff-line measurements