Near-field dispersion of radioactive nuclides from nuclear power plants under different meteorological conditions

The dispersion of radionuclides released from nuclear power plants (NPPs) is strongly affected by meteorological conditions, leading to pronounced variability in near-field concentration distributions. Therefore, a systematic investigation of radionuclide dispersion under different meteorological conditions is essential for environmental safety assessment of NPPs. In this study, the effects of wind direction, wind speed, and atmospheric stability on radionuclide dispersion were investigated using a computational fluid dynamics (CFD) model validated by on-site tracer experiments conducted at an NPP in China. The results show that wind direction determines the primary plume pathway and significantly influences pollutant accumulation by altering the degree of downstream flow obstruction caused by surrounding buildings. Wind speed governs plume rise and dispersion efficiency: stronger winds suppress vertical plume development and enhance turbulence mixing, thereby shortening horizontal transport distance and increasing breathing-level concentrations. Atmospheric stability further modulates dispersion through buoyancy-driven stratification. Under southeasterly (SE) winds at 2 m s^-1, the breathing-level concentration under stable stratification was approximately 4.65 times higher than that under unstable stratification. This study provides quantitative insights into the effects of meteorological conditions on radionuclide dispersion and a preliminary reference for assessing radiological risks and formulating emission management strategies around NPPs.