CFD simulation of the resuspension release of radioactive aerosol particles from contaminated sites
[Objective]Radioactive materials may enter the soil through atmospheric deposition,surface water,and groundwater pathways,resulting in radioactive contamination.Physical disturbances caused by natural winds or anthropogenic activities may cause particulate matter in the soil to be resuspended from the ground into the air.Some nuclides(e.g.,uranium)that are difficult to transfer to the human body through the food chain are likely to be inhaled in the form of resuspended particulate matter and cause internal irradiation.Therefore,the resuspension behavior of radioactive particulate matter must be investigated for the control of suspended particles.CFD(computational fluid dynamics)studies are mostly carried out on the resuspension of particulate matter in the pipe wall;only a few CFD numerical simulation studies have been conducted on the resuspension release of particulate matter from contaminated soil.[Methods]In this work,a CFD simulation of the resuspension release of radioactive aerosol particles from a contaminated site is carried out.First,the resuspension of radioactive aerosol particles caused by the air inlet is achieved,and the influence of the air inlet and exhaust outlet settings on the distribution characteristics of the airflow field is then analyzed.In the simulation,the air supply port is set as the velocity inlet,and the air velocity of the air inlet is set to 10 m/s.The air exhaust port is set as the outflow boundary,the wall is set as the solid-wall boundary condition,and the ground surface is set as the surface source for generating aerosol particles.The generated aerosol particles have a size of 2.5 pm and a density of 1.65 g/cm3.The discrete phase model is chosen to solve the gas-solid two-phase flow,and the transient state is used to calculate the motion-diffusion characteristics of the resuspended aerosol particles.To determine the state of particulate matter and the trajectory of the motion with time and space,the coupled SIMPLE algorithm of pressure and velocity is selected with the standard pressure and the second-order on-wind discrete format,and the turbulence model is adopted as the standard k-e model.According to the resuspension motion of the aerosol particles,the ventilation of the air inlet violently disturbs the airflow in the box,forming an approximate left-right symmetric airflow field in the box.[Results]Simulation results show that:1)when the inlet wind speed is 10 m/s,the airflow inside the resuspension box is uniformly distributed,and the vortex flow is sufficient to resuspend the radioactive aerosol particles on the ground.In addition,the amount of resuspension of particles is large,which is convenient for aerosol sampling and measurements.2)The simulated wind speed of the resuspension box near the ground is within the range of the ground surface wind speed in the area and thus can be applied to characterize the effect of surface wind speed on the resuspension of particles in this area.[Conclusions]This simulation provides a basis for the experimental design of the deposition and resuspension of radioactive aerosol particles.The findings provide guidance for the radiation protection of people working or moving in radiation-contaminated areas.
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