Aerosol particle size of radon progeny is the key parameter of the radiation dose conversion coefficient in radon progeny. It is necessary to develop a measuring device for the aerosol particle size of radioactive aerosol to measure the aerosol particle size distribution of environmental radon progeny. Inertial impactor is a kind of widely used particulate classification sampler.

This paper aims to design and implement an impactor applicable to radon progeny aerosol with a cutting size of 1 μm.

First of all, several kinds of inertial impactors were analyzed on the basis of aerodynamic theory, the design parameters of the impaction sampler structure, such as the diameter of the collecting plate, the distance between the collecting plate and the inner wall, the distance between the nozzle and the collecting plate, the height of the nozzle, were simulated by using computational fluid dynamics (CFD) analysis software Fluent and discrete phase model. Then, based on simulation results, a set of optimized design parameters were obtained and a porous impingent sampler was implemented for radon progeny aerosol. Finally, this impactor was calibrated by a GRIMM11-D aerodynamics particle size analyzer in a laboratory.

The optimized design parameters show that the nozzle distance D, the nozzle height T, the distance S from the nozzle to the collecting plate, and the nozzle diameter W have relationship of D/W=1.5~3.5, T/W=1~5, S/W=1. The experimental calibration results of designed porous impingent sampler are basically consistent with that of CFD numerical simulation with d_p50=(1±0.07) μm, σ_g1=1.33, σ_g2=1.35, and the cutting particle size of the impactors meets the practical application requirements.

This paper focuses on the design of an impactor sampler. Through simulation and comparison tests with ELPI⁺ instrument, the effective cutting of 1 μm particle size is realized, which provides convenience and ideas for the further optimization design and online particle size fractional measurement of radioactive aerosol.