Simulation of Pollution Emissions from Multi-Source Nuclear Production Sites Based on Probabilistic Method with Joint Frequency

To address insufficient representativeness and the potential risk of the underestimation of the long-term atmospheric diffusion assessment of nuclear facility gaseous effluents, a CFD numerical simulation framework based on annual joint-frequency weighting of 16 wind directions, 6 wind speed classes and 6 atmospheric stability classes is proposed and applied to a representative multi-source nuclear facility. The regulation law of near-surface flow field of the building complex and the diffusion characteristics of uranium aerosol is analyzed. The results indicate: Complex building matrix facilitates the formation of recirculating wake regions, which may serve as potential zones for aerosol accumulation. The uranium aerosol concentration weighted by joint frequency presents a distribution characteristic of central agglomeration and asymmetric gradient attenuation. Compared with the single most-frequent meteorological scenario, the joint-frequency-weighted field shows a higher expected peak and a 237 m shift in peak position. This shows that the joint-frequency weighting framework can reduce directional bias and underestimation of hotspot extent relative to a most-frequent meteorological condition. The method may provide quantitative support for refined radiation protection management and the environmental monitoring layout of nuclear facilities.