Small-scale deposition behavior of radioactive plutonium aerosols in hilly terrain

Plutonium can be an important radionuclide that may be released during nuclear accidents, but its deposition behavior is insufficiently studied, leading to inaccurate radiological consequence assessment of nuclear accident. Plutonium is an important radionuclide that may be released during nuclear accidents, yet its deposition behavior remains insufficiently understood, leading to uncertainties in radiological consequence assessment. By comparing cylindrical and variable-diameter initial smoke clouds, the effects of cloud morphology on aerosol dispersion and deposition are quantified, and the sensitivities of five key parameters are evaluated. Results show that terrain-induced flow governs aerosol spatial distribution, whereas the initial cloud shape controls particle transport. The cylindrical cloud model produces relatively uniform deposition (28.6% in the windward region, 11.7% in the hilly region, 9.53% in the leeward region, and 50.1% escaping through the outlet). In contrast, the variable-diameter smoke-cloud model exhibits stronger downstream transport, with 70.57% of the released mass escaping through the outlet. Particle size also strongly affects deposition. Large particles (90–450 μm) produce localized near-field contamination, whereas small and medium-sized particles (0–90 μm) contribute to far-field inhalation risk. Sensitivity analysis indicates that the turbulence dissipation constant C_ε2 exhibits the strongest overall association with the regional responses in the cylindrical smoke-cloud model and remains influential in the variable-diameter model, while the ground roughness exponent α and particle-size distribution parameter n show strong spatially dependent associations with selected regional responses. The proposed CFD-DPM model and sensitivity analysis framework provide theoretical and methodological support for contamination assessment and emergency decision-making.