The Program Development Of Neptunium’s Speciation Simulation In Groudwater

Programming geochemistry software,that is,analyzing and solving the geochemical model that established by mathematical formulae and chemical reaction equations,is currently an important method to research on the migratory behavior of nuclides,which comes from the high level radioactive waste repository.The migration behaviors of nuclides are closely related to the chemical forms.According to the composition and the concentration of the research system,the chemical speciation distribution of corresponding elements in this system could be obtained by calculating the possible species and their concentration based on reaction equations,corresponding equilibrium constant and related thermodynamic data.In the study of migration behavior of radionuclides in the geological layer from the high level radioactive waste in disposal repository,Np is one of the key elements.Np is chosen as the object in this study and the calculations are carried out about the chemical speciation of neptunium in groundwater.By analyzing the interactions between the Neptunium and anions like CO₃^2-,OH^-,SO₄^2-in the groundwater,considering the influences of plentiful cations like Ca⁺and Na⁺,oxidation-reduction of Neptunium of various valence during the equilibrium process and the influence of temperature,pH and Pe…to it,the ionic strength model,redox model,complex reaction model and precipitation reaction model could be modelled with combination of relevant knowledge of water chemistry of precipitation-dissolution,complexation,redox reaction types based on mathematical methods,.Then,the PHP language programming is used to calculate and analyze the the chemical speciations of Neptunium.Through the examples,it’s found that Neptunium in the groundwater is in the form of NpO₂⁺,comprised 87.29%of the total.The second most common is in the form of NpO₂CO₃^-,comprised about 12.43%in total amount and also microcrystalline NpO₂SO₄^-、NpO₂（CO₃）2^3-、NpO₂F、NpO₂（OH）.The computed results are consistent with the conclusion of PHREEQC,which validates its reliability to some extent.At the same time,the influences of pH,Pe and temperature to the valence state of Neptunium are analyzed.The computed results of two programs show that the change in pH doesn’t have impact on the valence states,but does influence the existing forms.Within the computable range of this system,the content of NpO₂⁺and NpO₂CO₃^-is always high,which differentiates with the content of other existing forms.The distinctions of computed results are mainly caused by the differences in the initial value selection method,iterative calculation method in the iteration and data of database.After contrasting and programming check,the program could basically used to calculate the existing forms of Neptunium in the groundwater...