Atmospheric Diffusion Model Of Airborne Radionuclides From Nuclear Accidents In The Marine Environment

With the development of nuclear power technology,island nuclear power stations and floating reactors may be built in the future.Due to the limited emergency access space of the island,once a large-scale nuclide leakage occurs,the staff on the island will have a long stay in the contaminated area.In addition,for all nuclide proliferation in the Marine environment,it is necessary to evacuate the islands and ships in the path of proliferation and conduct nuclear safety protection for the inland areas where nuclides are landed.However,the Marine environment has different underlying surface characteristics from the inland nuclear power plants.In order to improve the accuracy of the gas-borne radionuclide diffusion model under the nuclear accident in the Marine environment,this paper studied the influence rule of the special cushion on the diffusion in the Marine environment.The main contents and results include:According to the theory of influencing factors of nuclide atmospheric diffusion in complex underlying surface environment,the simulation model of typical island underlying surface was established,including the atmospheric space scope and wind speed profile.The complex underlying surface environment of island nuclear power plant is modeled in detail,including: 1,Four nuclear power units;2,Workshop in the factory;3,Island platforms above sea level;4,the mountain around the island.Meanwhile,according to the similarity theory,the simulation experiment is carried out under the active control wind tunnel with the scale of 1:1000.The accuracy of CFD simulation is verified by comparing the CFD experimental data of aerosol diffusion measured by laser image technology,which provides experimental support for subsequent simulation.The effects of geomorphic environment,wind field and nozzle velocity on diffusion were studied.The results show that the island underlay surface will increase the maximum diffusion factor of nuclide ground and the location is closer to the export.In the case of low wind speed,the deviation between the calculated results of the ground maximum diffusion factor in the numerical simulation and the gaussian plume model is significantly larger than that in the case of high wind speed.The increase of the export velocity will increase the disturbance of the tall mountain to the plume and make the surface axis diffusion factor form two peaks.There is a linear relationship between the simulated value of the maximum ground diffusion factor and the calculated value of the gaussian plume model when the velocity of the export is changed with the same underlying surface,nozzle position and wind speed.According to the linear relation,a modified method for gaussian plume model is proposed to improve the calculation accuracy.The island platform will cause obvious disturbance to the gas-borne radionuclide diffusion near the exit,b but only within one kilometer of the downstream.It has little influence on the overall distribution of the axial diffusion factors,the location and the maximum diffusion factors.In addition,when the distance between nuclide outlet and edge is the same,the maximum diffusion factor of the ground axis of downdraught decreases with the increase of platform height.