应用MOCA程序设计煤料PGNAA实验装置

为促进国内煤料瞬发γ中子活化分析（prompt gamma neutron activation analysis, PGNAA）技术开发，本研究使用基于蒙特卡罗模拟方法的MOCA程序对煤料PGNAA技术常用中子源²⁵²Cf进行模拟建模，并对²⁵²Cf中子源在煤料和常用慢化体聚乙烯中的中子场分布进行模拟计算，得到了源距与中子通量的关系曲线。通过模拟计算的结果，结合煤料PGNAA的测量过程和实验室情况，设计了既可表征大批煤料PGNAA过程又可实现辐射防护的实验装置。使用该装置开展实验室实验，取得了具有明显特征峰的实验谱图和良好线性的灰分标定系数，表明设计的实验装置具有适宜性，可利用该装置对煤料PGNAA进行进一步实验室研究。

Design of the Coal PGNAA Device by MOCA Program

Prompt gamma neutron activation analysis (PGNAA) is a method for quantitative analysis of multiple elements, which is applied in the analysis of coal, concrete, and solid mine. For the purpose of coal PGNAA study, experiment in lab is necessary. But, restricted by the situation of lab, infinite coal material is impracticable. So, designing a coal PGNAA experimental device to stand of the process of PGNAA of bulk coal and achieve the goal of radiation protection is very practical. Monte Carlo is a kind of mature method, by which can simulate the transportation of neutrons and the process of the interaction of particles and material, and calculate the complicate-constructed nuclear incidents. So, using the Monte Carlo method to design experiment of nuclear reactor is common. This research used a special Mont Carlo program-MOCA to design a coal PGNAA experimental device to reach the aim of promoting the PGNAA technique. Firstly, the field distribution of ²⁵²Cf neutron source which was used in PGNAA common was constructed with MOCA. Then, by simulating the neutron field formed by²⁵²Cf neutron sources in bulk of coal and polyethylene, the relationship curves of neutron flux and its distance from the source were obtained. Based on the principles of infinite coal material and radiation protection, according to the curves obtained in the previous work, an experimental coal PGNAA device was designed. Finally, the PGNAA experiments of seven different components of coal material were carried out with the device. The spectrums from lab experiment showed element characteristic peaks obviously and quantitative analysis results with good linear. The successful experiment proved that the device was designed reasonably, and MOCA program was an effective method in the study process of coal PGNAA and could be used more in the further.