Research On The Numerical Modeling Of Offshore Radionuclide Dispersion Based On CFD

The application of nuclear energy has become increasingly widespread for its clean and reliable property.Radiation safety and radioactive pollution caused by nuclear accidents have always been the focus of attention.The leakage of radioactive materials from small modular reactors of offshore platforms,floating nuclear power plants and coastal nuclear power plants may cause severe radiation pollution in offshore areas.The studies of radionuclides dispersion mechanism and simulation in offshore areas have been carried out to reveal the variation of radionuclides concentration and to predict highly polluted waters,which is of great significance for early decision-making and rescue of nuclear accidents.In this paper,a three-dimensional offshore radionuclide dispersion model based on Computational Fluid Dynamics(CFD)is developed to accurately simulate the spatial and temporal distribution of liquid radioactive materials in offshore areas.The numerical calculation process is implemented by an open source CFD toolkit,OpenFOAM.The main work is briefly described as follows:(1)An automated unstructured grid generation method was developed to fit the complex sea floor topography and shorelines in offshore seas fast and accurately.The highly irregular offshore geomorphology is precisely meshed by a finite volume method combining with hexahedral and polyhedral grids.At the same time,the conservation of physical quantities within the computational area is guaranteed.(2)A CFD-based radionuclide dispersion simulation method was developed to carry out a high-precision calculation for radioactivity concentration distribution in the offshore waters.A good universality standard k-? turbulence model was introduced by using Reynolds' time-average equation method.The transportation state of radionuclides in the offshore area is objectively simulated through the optimization of radionuclide dispersion equations and the input of dynamic boundary conditions,which improves the calculation accuracy of the model.(3)The model and method were verified by the data of waste tritium water from the nuclear fuel reprocessing plant at Cap de La Hague,France.Through comparison with the sea surface monitoring data and the calculation results of a third-party model,the correctness and accuracy of the model is verified,and the sources of errors are analysed.The results preliminarily show that the numerical modeling technology of offshore radionuclide dispersion based on CFD method can be used to predict the radiation consequences of accidental or conventional emissions from nuclear facilities,which provide decision support for emergency response.