The analytical sensitivity of U measurement by delayed neutron counting method may be improved due to the Delayed Neutron Detector installed at China Advanced Research Reactor (CARR) in China Institute of Atomic Energy (CIAE) with the highest neutron flux in Asia.The position of 3He gas tubes,the size and geometry of CARR Delayed Neutron Detector (CDND),Cd foil and lead walls were optimized to obtain a sufficiently large neutron counting efficiency for the delayed neutrons induced by reactor neutrons on the 235U nuclide using MCNPX code.The 235U sample was irradiated using a 30kW Miniature Neutron Source Reactor at China Institute of Atomic Energy and counted using the CDND.The test results show a satisfactory performance with the neutron detection efficiency being about 1.3％ of CDND within an error being 0.2％ of MCNPX.%中国原子能科学研究院先进研究堆(CARR)具有亚洲最高的中子注量率,对提高缓发中子测铀分析灵敏度有积极意义.在CARR建设缓发中子探测器,将进一步提升我国缓发中子测铀的水平.应用蒙特卡罗模拟程序(MCNP)对CARR缓发中子探测器中3He正比计数管的位置,中子慢化-中子和伽马屏蔽体的尺寸和几何进行了优化设计,并利用中国原子能科学研究院30 kW微型反应堆(微堆)垂直孔道辐照235U样品,对设计的探测器效率进行了验证,测量的探测效率为1.3％,比模拟结果高0.2％.
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