Chemical Species Of Radionuclide Np In The Groundwater By Simulation Calculation

Nuclide neptuniun (Np), because of its long half-life, high mobility and chemical toxicity become an important one of nuclear contamination. Its chemical behavior in groundwater is more complicated. The existence form of understanding of Np in the environment to learn its migration performance and the regularity of activity, is the one of the basic problems of geochemistry. In recent years, computer simulation technology is widely applied in the field. In this paper, write your own program and applied to the research of the chemical form of Np in northwest district groundwater.In this paper, the chemical thermodynamics balance analysis mode and the geochemical condition close union, using the element hydrogeochemical thermodynamics analysis method,using C language to write computer programs, simulation Np existence form and the concentration of each form. The simulation results showed that the pH value is 7.24, the temperature is 16 ?, Eh value is 0.345 V, neptunium in the groundwater is mainly exists in the form of Np (V), the main existence form NpO2+,accounting for 96.47%, followed by NpO2CO3-,NpO2(OH),NpO2SO4-,NpO2(CO3)23- respectively accounted for 1.91%,1.12%,0.186%, 0.00155%. A very small amount of neptunium to Np (IV) and Np (VI) form, can be ignored. While the situation there is only pentavalent Np were simulated, found that when groundwater when only pentavalent Np, mainly in the form are Np02(OH) ,NpO2SO4- and NpO2(CO3)- the concentration are 97.4%, 2.13%, 0.29%, 0.18%.Using geochemistry program PHREEQC simulation in the presence of Np form in groundwater, Simulation results are basically identical with self-programming. Np mainly forms are NpO2+, NpO2CO3- and NpO2(OH) and various forms of share concentration ratio difference between the simulation results and self programming not more than 5%.Application of self-programming and PHREEQC investigation of groundwater pH value,temperature, Eh value, Np concentration, concentration of HCO3- and SV42- concentration on Np exist form. Simulation results showed that the pH value will affect the Np valence and the chemical form of presence in groundwater. When the pH value is between 3 and 4, mainly in the form of Np is NpSD42+; when the pH is greater than 4 is less than 8, its main form is NpO2+, when the pH is greater than 8 when, the main form is NpO2(OH). The analysis of the effect of Eh value on the chemical forms of Np,The simulation result of self-programming and PHREEQC the second simulation results show that Eh value Eh value is almost no effect on the existing form of neptunium in groundwater, its main form is pentavalent NpO2+,However, PHREEQC simulation results of one show when Eh values at between -5V and -2V, mainly in the form of Np is Np(OH)4(CO3)2-; when the Eh is greater than 2, is NpO2+. Investigation Np concentration and SO42- concentration on discovery will not affect the existing form of Np. HCO3- concentration does not affect the existence of Np valence but it will affect its chemical form.At low concentration of HCO3- mainly pentavalent NpO2+;when the high concentration of HCO3-, mainly NpO2CO3-.