Comparison of Atmospheric Dispersion Factor in Complex Terrain

Calculations of annual and accident atmospheric dispersion factors (ATFs) for nuclear power plant environmental impact assessment are usually based on the safety series of IAEA and regulatory guides of U.S. Nuclear Regulatory Commission. However, as for the sites in complex terrain especially for low wind speed and calm conditions, it is needed to evaluate the validity and conservation of atmospheric dispersion model and parameters. In this paper, the site chosen for the test was the Fuling nuclear power plant site in Chongqing, which was selected primarily on the basis of the available atmospheric data. The annual ATFs were calculated through simulating the 8760 hourly releases of radioactive nuclides using the three dimensional objective diagnostic wind field model and Lagrangian trajectory puff model. The comparison with the ATFs calculated by the usual models shows that the annual ATFs from hourly simulations is about 2.6~3.4 times depending on different nuclide. Therefore, it should be careful to apply the usual models to the site with complex environmental conditions like Fuling site, and also to analyze the conservative application of the models and parameters. Many works for the accident ATFs evaluation should be also developed and examined.