The Optimal Design Research Of Graded Screen Arrays Used For Sampling Radon Progeny

Radon and its daughters have great danger to human. Particularly, the radon progeny can cause internal exposure after it has gone inside human body. The different size radon progeny has different deposition shares in the different regions of human body. So the size distribution and unattached share of radon progeny should be taken measurement and done some research. Graded Screen Arrays(GSA) is a kind of international-accepted radon progeny sampling device. But there are little researchers about GSA’s optimal design in its structure and measurement method. This paper does some researches about the optimal design of GSA.For optimizing the structure of GSA, this paper is based on the Fan Model Filtering Theory and Computational Fluid Dynamics. The GAMBIT software is used to build the model of graded screen arrays and stream guidance device with 8 holes. The FLUENT software is used to simulate the velocity distribution of different screens and filter. And the change of velocity distribution of different screens is also simulated after adding the stream guidance device. So the optimal design of GSA can be gotten from the simulation. Then many important parameters of filter and screen are measured from the experiment. And the two sampling device are used to take the experiment in the radon chamber. It is verified that the improved GSA can sample more unattached radon progeny.For optimizing the measurement method of GSA, this paper is based on Markov Fast Potential Energy Concentration Measurement Method. The radon progeny potential energy concentration conversion factor K of different screens and filter is solved in the different condition of progeny equilibrium ratios. Meanwhile, the radon progeny potential energy concentration computational formulas are gotten. The limitation of simultaneous measurement by many detectors is made up. This research may provide some ideals for making the new one detector radon progeny measurement in the future.Simulation and experiment can certify that after adding the stream guidance device, the radon progeny can keep stable steady laminar flow in the GSA than before. The improved GSA has better collection efficiency of unattached radon progeny than the traditional GSA. It can provide some reference to the research in the future.