CARR堆瞬发伽马活化分析系统的初步设计

The Design of PGNAA Facility on CARR

基于中国先进研究堆(CARR),采用蒙特卡罗方法设计并优化了瞬发伽马中子活化分析系统,确定了该分析系统的整体结构、关键组成部件的物理和几何参数。20cm的单晶铋过滤器能够提高中子束中热中子的份额,也极大地屏蔽了来自堆芯的伽马射线;多层材料单段柱型准直的设计能够保证照射位置较高的中子注量和较低的本底。整个装置的屏蔽设计充分考虑到了材料的质量、体积和成本等因素,通过MCNP模拟结果最终确定了各屏蔽材料的尺寸。模拟结果显示,所设计的装置能满足辐射防护和低本底的要求,达到了最初的设计目标。

The PGNAA facility at CARR was designed and optimized using Monte Carlo methods. The general configuration as well as physical and geometrical parameters for the key components of the facility has been defined. A neutron filter of 20 cm length mono- crystal Bismuth could result in a high thermal neutron flux with low epithermal neutron and gamma ray contaminations. The collimator with a ＇sandwich structure~ was selected from three candidate structures for its superior performance in obtaining high neutron flux and low background. Factors including the weight, volume, machinability, cost low bach- ground at the detector position were taken into account in the optimization of the radiation shielding design. The simulation results showed that the design meets the requirements of radiation protection, and low gamma background.