Analysis of the radioactive atmospheric dispersion induced by ship nuclear power plant severe accident

Highlights: • The radionuclide diffusion released by ship reactor after a severe accident on ocean is analyzed. • The Lagrangian particle tracking model is employed to study the nuclide diffusion. • The radionuclide concentration in the air will be effected significantly by the sea absorption. • The sea absorption has different influence on nuclide distributions at different emission height. - Abstract: For the nuclear powered ship, the radionuclides will be released near the sea surface after a severe nuclear accident. The influence of sea surface on the atmospheric diffusion of radionuclides cannot be ignored. Based on the Lagrangian particle tracking model, the simulation model for atmospheric diffusion of radionuclides above the sea was established. The influences of sea absorption on atmospheric diffusion of radionuclides emitted at different heights were analyzed. It is shown that if emission height is low, the time-integrated concentration of radionuclides in the air will be reduced significantly by the sea absorption. The lower the discharged height is, the more rapidly the concentration of radionuclides in the air near the source decreases. If the emission height is high, the time-integrated concentration of radionuclides in the air will increase firstly and then decrease with the increase of distance. The higher the emission height is, the lower the time-integrated concentration of radionuclides in the air near the sea surface is, and the smaller the amount of radionuclides absorbed by the sea is.