Monitoring method for neutron flux for a spallation target in an accelerator driven sub-critical system
Monitoring method for neutron flux for a spallation target in an accelerator driven sub-critical system
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DOI：
10.1088/1674-1137/40/7/076203
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发表时间：
2015-08
影响因子：
3.6
通讯作者：
Q. Zhao;Zhiyong He;Lei Yang;Xueying Zhang;Wenjuan Cui;Zhiqiang Chen;Hushan Xu
中科院分区：
文献类型：
--
作者：
Q. Zhao;Zhiyong He;Lei Yang;Xueying Zhang;Wenjuan Cui;Zhiqiang Chen;Hushan Xu
本文研究了加速器驱动次临界（ADS）系统中子靶的中子通量监测方法。首先，针对空间分布中子通量的空间变化特点，提出了多点测量技术，即在多个垂直位置测量空间分布中子通量。为了解释为什么通量应在多个位置进行测量，我们研究了中子产生的钨靶轰击的250 Me V-质子束Geant 4为基础的蒙特卡罗模拟。模拟结果表明，在中心位置的中子通量是高达三个数量级高于在较低的位置的通量。其次，通过建立裂变室（FC）测量的裂变率与裂变中子通量之间的关系，发展了一种有效的测量裂变中子通量的方法。由于这种关系对于FC是线性的，因此使用恒定的校准因子来从测量的裂变率导出中子通量。这个校准因子可以从散粒中子的能谱中提取出来。最后，我们已经评估了建议的校准方法，在ADS系统的环境中的FC。结果表明，该方法的功能非常好。
In this paper, we study a monitoring method for neutron flux for the spallation target used in an accelerator driven sub-critical(ADS) system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique,i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 Me V-proton beam with Geant 4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber(FC), by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well.