Studyonthe Methodof Measuring Radon Progeny Aerodol Size Distributionby Using Gradedscreenarray

The study of radon progeny aerosol size distribution involving nuclear science,environmental science and other disciplines is the basis of the radiation environment protection and management,the dose deposition calculation of lung tissue area,the development of radon progeny measuring instrument and other fields.Radon progeny aerosol does harm to human health in the environment,so this paper will explore its size distribution characteristics.At present,there are different measurement methods of particle size distribution at home and abroad,many of which fail to measure the ultra-fine nano-aerosol particle size,and there are fewer methods and instruments for measuring the radioactive aerosol particle size.The adoption of measuring method of graded screen array not only solves these problems,but also makes the activity particle size distribution of the unattached radon progeny aerosol available.This paper,according to fan model screen collection theory,selects different sampling flow rate and mesh number contrast to other researches for the graded screen array system,and combined with the Expectation Maximization Algorithm,backsteps the formula of size distribution and calculates the maximum activity fraction of each radon progeny aerosol particle size through iterative algorithm.This paper proposes a method of dividing the three particle size intervals to calculate the collection efficiency separately,highlighting the wire collection mechanism of different radon dendrite aerosols and simplifying the calculation process of collection efficiency.In this paper,the three-stage method is used to measure the equilibrium ratio of radon progeny in standard radon chamber within only single channel α spectrometer case and on this basis,the experiment is conducted to measure and calculate the concentration of radon progeny collected by the graded screen array sampler.By using the graded screen array method,the activity size distribution of radon progeny in radon chamber is displayed as a bimodal structure,manifesting that the activity median diameter of the unattached is 0.82 nm while the activity median diameter of the attached is 463.45 nm.By comparing the analysis,it is found that the activity median diameter of the unattached is basically the same as that of other research institutions,but the activity median diameter of the attached has a certain gap compared with the measurement results of the scanning mobility particle sizer in this paper and other literature data.The results of this paper show the advantages of graded screen array in measuring the size distribution of radon progeny aerosol,and the reasons for the large deviation of the activity median diameter of the attached may be due to this paper is different from the measurement environment,aerosol type and measurement principle of other research results.