Study On Multi-fan Wind Tunnel Simulation Of Atmospheric Dispersion In Nuclear Power Plant

In order to alleviate the harm of nuclear accident,the atmospheric diffusion process of nuclide release from nuclear accident should be accurately estimated when a nuclear accident occurs.The gaussian model has been widely used for rapid estimation in our nuclear power plant,however,the applicability of the model needs to be further verified in different sites and different meteorological environments,in which wind tunnel experiment is an important verification method.Traditionally,the atmospheric boundary layer was simulated by the passive wind tunnel with tracer gas played as the airborne radionuclides.However,the passive wind tunnel has poor adaptability to boundary layer simulation and the complicated adjustment process,so the simulation accuracy of wind velocity profile of atmospheric boundary layer is poor.Because of the limitation of gas sampling,there are few measuring points that can be used for diffusion analysis,so the development and verification of atmospheric diffusion models have been limited.In order to improve the accuracy of wind tunnel experiment,this paper presents a new experimental way to study atmospheric dispersion in nuclear accident.The main contents and results include:(1)The multi-fan wind tunnel technology in the wind-resistant field has been introduced into the study of atmospheric dispersion of nuclear accidents,and a multi-fan wind tunnel was designed and built.The mechanical design and construction of 10(rows)×8(columns)multi-fan wind tunnel were completed,and a unified control scheme was designed to achieve independent and remote control of all fans.The contraction section shape of each tunnel was 3-dimensional designed and aerodynamic analysed by the CFD method;the wind speed measurement and feedback structure in the two-dimensional plane is designed and the closed-loop control is implemented in the simulation of the atmospheric boundary layer;finally,The multi-fan wind tunnel has been proved that it is valid to simulate the atmospheric layer characteristics.Compared with the traditional passive wind tunnel,the speed and accuracy of the simulation are greatly improved.(2)A method of measurement and analysis of the multi-fan wind tunnel is designed.Aerosol particles are released as diffusion tracer,photographed by the PIV device in the laser area,and the particle images are analyzed by the mathematical statistics.In addition,this method is applied to analyze the particle characteristics around the topography and main buildings of the Shidaowan nuclear power plant.The results are in good agreement with the P-G diffusion parameters and the validity of the method is verified.