Uranium, Strontium Migration Patterns And Geochemical Barrier Materials

The very low level waste (VLLW) from decommission was normally buried in nearly place according to the international tradition. In the same time, engineering barrier and geochemical barrier were often combined to insure the securer of the waste disposal site. Geochemical barrier is a new barrier to the contaminated nuclide's migration in the groundwater, through adding mineral additive according to the disadvantage factor of the rock and soil in site.In this paper, the theoretical calculation of species and deposit condition about Uranium and Strontium was performed in one buried disposal site of very low-level radioactive,and the selection materials for the geochemical engineering barrier was studied.The species of Uranium and Strontium in groundwater were obtained via theoretical calculation.the deposit condition were get also. Then the selection of basic materials and additives was accomplished by static absorption experiment,and the best inartifical material was choosed for geochemical engineering barrier in the burned site.The theoretical calculation for the chemical species and migration behavior of uranium in groundwater were accomplished by combining the thermodynamics balance analysis mode, the geochemical condition and the known thermodynamics data. The results indicated that there was not U(IV) in the groundwater under the oxidation condition, and the overwhelming majority (more than 99%) of U(VI) in the groundwater exit as the complex species, such as UO₂(CO₃)₂^2- UO₂CO₃⁰, and UO₂(CO₃)₃^4- while the other species as UO₂(OH)₂⁰, UO₂(OH)⁺, or UO₂²⁺, account for less than 1%.The Eh for reduction of U(VI) to UO₂ in groundwater of a radioactive wastedisposal site was calculated with Nernst equation, and the various factors influencing the Eh were discussed. The results show that the Eh for reduction of...