Research on Source Characteristics of Radionuclide Diffusion in the Ocean Under Oceanic Radioactive Events

All operational and under construction nuclear power plants in China are distributed in coastal areas presently. Facing the problem of spent fuel from nuclear reactors, we are also actively promoting the system construction of combined transport with highway, ocean and railway. In case of a nuclear leakage accident, radionuclides will diffuse through the atmosphere and the ocean, and pollute the ecological environment. To solve the problem of radionuclide diffusion in the ocean, we first need to solve the source term problem. The study on source characteristics of radionuclide diffusion in the ocean under oceanic radioactive events plays an important role in simulation and emergency decision-making. The meaning of source term and unit parameters were given, and types, forms and release modes of radionuclides were analyzed under nuclear leakage accidents. The storage and release of radionuclides were calculated. Then the dry and wet deposition fluxes of radionuclides were calculated. The results show that ¹³¹I, ¹³⁴Cs and ¹³⁷Cs are the most important radionuclides in radiation dose evaluation and they will be in the form of C_SI and CsOH under nuclear leakage accidents. Radionuclides are released into the environment in the form of micron aerosol. Radionuclides entering the ocean include direct release and atmospheric radionuclide deposition. The dry deposition flux is 3 orders to 4 orders of magnitude lower than the ground radionuclide concentration. The wet deposition flux within 300m is much larger than the dry deposition flux, and the wet deposition flux outside 300m is about 1 order to 2 orders of magnitude larger than the dry deposition flux. It provides a prerequisite for the calculation of radionuclide diffusion in the ocean under oceanic radioactive events.