3D numerical simulation of radionuclides atmospheric dispersion in Chinese nuclear safety regulation.

For increasing the regulation accuracy and efficiency, commercial computational fluid dynamics (CFD) software Fluidyn‐PANACHE was induced to assist in the analysis of typical radionuclides atmospheric diffusion for the Chinese nuclear safety regulation. The atmospheric dispersion simulation system that used three‐dimensional CFD methods, combined three‐dimensional GIS, and multiple technical methods, such as boundary values calculation, body‐fitting mesh generation, and refinement, was established to simulate and discuss the local wind field characteristics, pollutant transportation, and spatial distribution patterns under spot or constant meteorological conditions following unsteady (real time) or steady methods, respectively. This method can be used to reasonably simulate the turbulent and circumferential flow around large cooling towers in the inland nuclear power plant, compensating the shortage in subtleness of the standard Gaussian model, as well as shortage in realizing multiwind direction simulation in the calculation by the traditional CFD model. The calculation results of annual average atmospheric dispersion factor under normal operation indicated the seasonal differences, with maximum average dispersion factor in autumn, which were consistent with those suggested by Gaussian mixture model. Consequently, it is reasonable to avoid refueling overhauling in autumn to diminish pollution. The CFD numerical simulation method, which has a high agreement with the results of physical tests such as wind tunnel test, provides a new reference for the nuclear safety review of inland nuclear facilities in China. [ABSTRACT FROM AUTHOR]