摘要:
[Background] The232Th(n,2n) reaction dominates the neutron generation, so the validity of the cross section data is significant in the thorium based reactor.[Purpose] In order to provide the data reference for the design of thorium based reactor, an integral experiment to measure the232Th(n,2n) reaction rate was carried out using the activation method in a polyethylene shell with DT neutrons. [Methods] In the experiment, thorium samples were arranged in the 0° direction to the incident D+ beam, and a Au-Si surface barrier detector was used to monitor the neutron yield and the fluctuation of neutron flux. [Results] After irradiation, the 84.2 keVγ ray emitted from231Th was measured by HPGe spectrometer, and the232Th(n,2n) reaction rate was then obtained. The thorium sample was in foil and powder respectively to eliminate the effect of the sample condition. Simultaneously, the experiment was simulated precisely using Monte Carlo N Particle Transport Code (MCNP) code in the ENDF/B-Ⅶ.1, ENDF/B-Ⅶ.0, and JENDL4.0 libraries. [Conclusion] The calculated values in the JENDL4.0 were in good agreement with the experimental ones, which can provide reference for the design of thorium based reactors.%232Th(n,2n)数据对于钍基反应堆研究十分重要,有必要针对其开展中子积分实验,因此,建立了聚乙烯球基准宏观装置,利用活化法在DT中子源下开展了测量232Th(n,2n)反应率的中子积分实验.实验中分别采用了钍粉末以及钍片两种样品形态,以消除实验样品状态对实验结果的影响,将样品置于与D离子入射方向成0°的位置进行辐照,利用金硅面α探测器进行中子产额监测以及中子注量波动监测.辐照结束后,利用高纯锗谱仪离线测量反应产物231Th发射的能量为84.2 keV的γ射线,得到232Th(n,2n)反应率值.同时使用MCNP(Monte Carlo N Particle Transport Code)在数据库ENDF/B-Ⅶ.1、ENDF/B-Ⅶ.0、JENDL4.0下对实验进行了精确模拟,数据库JENDL4.0下的反应率计算结果与实验符合较好.