水中大面积ZnS(Ag)闪烁体总α在线监测系统模拟设计

Simulation Design of on-Line Monitoring System for Gross Alpha in Water Based on Large Area ZnS(Ag)

采用Geant4软件对大面积ZnS(Ag)探测器有效探测体积、闪烁体厚度及半径、荧光收集效率进行了模拟,确定了闪烁体的最佳结构尺寸,并对探测系统整体结构进行了优化设计,最后对探测系统的最小可探测活度浓度进行了估算。理论设计的大面积ZnS(Ag)闪烁体对238U产生的α粒子的探测效率的模拟结果为0.005 2 s^(-1)/(Bq/L),探测系统的本底计数率为1 min^(-1),则探测器在16 h内即可实现0.5 Bq/L的测量目标。该研究对于总α放射性活度在线测量装置的研发具有重要的指导意义。

The effective volume of detector,the thickness and radius of the scintillator,and the fluorescence collection efficiency of the large area ZnS（Ag） detection system were simulated using Geant4,and the optimum structure of the scintillator was determined,then the structure of the detection system was designed,finally the minimum detectable activity concentration of the detection system was estimated.The simulated detection efficiency of the designed large area ZnS（Ag） for alpha particles produced by 238 U is 0.0052 ^-1/（Bq/L）,and the background counting rate is 1 min^-1,then the detection system can achieve the target of 0.5 Bq/L within 16 h.This design results have important guiding significance for the research and development of on-line monitoring for gross alpha.