Numerical Simulation Of Radioactive Material Diffusion Around Buildings

The utilization of new energy such as nuclear energy has gradually become the trend of energy revolution in the future.Improper discharge of radioactive waste has a great negative impact on the ecological environment.However,the research on the diffusion of radioactive materials has mainly focused on the medium and large scale.It has been proven that CFD is suitable for simulating the flow around buildings.In China,industrial and civil low-rise buildings are widely distributed,and most of them are double-slope roofs.Due to the multiple layout and structure of the double-slope roof building,the distribution of surrounding wind field is complicated.However,less attention was paid to the three-dimensional simulation of closed sloping roof buildings.The study of the influence of the building roof inclination on the diffusion needs to be further studied.In addition,most of the current research have focused on the flow and deposition of radioactive materials outside the building,whereas less study of the diffusion law from outdoor to indoor.In this paper,the open source software,OpenFOAM was carried out to simulate the atmospheric diffusion of radioactive materials around closed-slope roof buildings and opening-windows buildings.Based on the SIMPLE algorithm,the component diffusion equation containing the source term is added.The effects of inflow wind velocity and building roof inclination on the diffusion around the closed-slope roof buildings were studied.The results show that when the inflow wind velocity increases,the atmospheric turbulence increases and radioactive material diffuses more fully.The arrangement of buildings influences the plume height,the vortex,and the transport of radioactive material between canyons.The higher the plume is lifted,the more diffuse it is.In the canyons of two buildings,the concentration near the wall is affected by the distribution of its wind field.The influence of inflow wind velocity and window distribution on the diffusion around the opening-windows buildings was studied.The results show that the diffusion effect increases as the inflow wind speed increases.The generation of vortex is related to the windows distribution.When the windows are perpendicular to the inflow wind,the radioactive material gathers near the indoor downstream wall.When the windows are parallel to the inflow wind,the concentration distribution inside and outside the building is opposite.The indoor concentration is uniform.Based on the simulated results of radioactive material concentration,the doses of humans that were internally irradiated by breathing around closed-slope roof buildings and opening-windows buildings were analyzed.Then their committed effective dose were estimated.The irradiated population was divided into infants,children,and adults.The absorption rate of radionuclides was divided into three categories: F,M,and S.The radiation effects of different age groups at different absorption rates were evaluated.Overall,the doses of irradiation in infants and children are similar,and they are significantly higher than those in adults,especially when the absorption rate is fast(F).Therefore,infants and children should be given priority protection when there is radioactive contamination.