用于核素在线瞬发伽马数据测量的热中子源设计

基于MCNP程序建立了西安脉冲堆热中子源设计的蒙特卡罗深穿透耦合屏蔽计算方法；采用MCNP临界源模型计算了热柱方腔前表面的中子、伽马平面源的参数，并与实验值进行了对比，给出了平面源的修正系数；基于中子、伽马等效平面源，采用新型硼铝复合材料以及铅、铋等材料，优化设计了热中子束流滤束装置，给出了热中子束流滤束装置的升级改造方案，得到热中子通量密度较原设计方案提高3倍、中子伽马通量密度比值大于10的平行热中子束，且束流外侧区域的中子、伽马本底剂量率接近0.025 mSv/h的辐射防护标准。

Thermal Neutron Source Design for Nuclide Parameter Measurement with On-line Prompt Gamma Ray Method

The Monte Carlo deep-penetration coupled shielding calculation method for the thermal neutron source design at Xi’an Pulsed Reactor was realized with the MCNP code. The parameters of neutron and gamma plane source at the front plane of thermal column square cavity were calculated with MCNP critical source mode and compared with the experiment value, then the correct factor for the plane source was given in this paper. Based on the neutron and gamma plane source, the thermal neutron filter was optimized with advanced borsic-aluminum material, lead, bismuth and so on. Then the upgrade scheme for the filter was introduced and the results show that the scheme can obtain high performance parallel thermal neutron beam, for which the thermal neutron flux density is increased by three times, the ratio of neutron over gamma flux density is greater than 10, and the background dose rate of neutron and gamma outside thermal beam is close to the radiation protection standard 0.025 mSv/h.