Ab initio Hartree Fock (HF) theory and Density Functional theory (DFT) have been used to predict the Gibbs free energy of formation (ΔGf0) for uranium (VI) hydrolysis complexes. B3LYP is a better method to calculate the chemical properties of the complex and large molecules. The calculations were performed in the presence of solvent (water) by using the dielectric continuum modeling PCM method as well as the revised Born model. The pressure parameter p=1354atm was used to reproduce the entropy of ions in solution. The calculated energy demonstrates that PCM model is better than Born model in calculating the hydration energy. The primary hydration shell has been included in the calculation. It shows that the B3LYP calculated results inclusive of the primary hydration shell and the PCM hydration energy have reasonable agreement with experiments.
A new cesium ion-sieve (Cs-IS) was developed by cesium ion extraction/introduction reaction with ZMPP. The investigation on its properties showed that Cs-IS not only remains the similar microcrystalline structure of ZMPP, but also carries forward the large exchange capacity for cesium and good chemical stability in the medium of 3mol/dm3 HNO3 from ZMPP. In the static exchange with the strong acidic simulated HLLW, Cs-IS exhibits high exchange rate for cesium and large separation factor βCs/M.
Water-glass and water-granite interactions in Beishan Area, a potential area for China HLW repository, have been studied using EQ3/6, a geochemical software package developed by the Lawrence Livermore Laboratory for use in modeling the complex geochemical processes that occur when aqueous solutions react with soil, rock, or solid waste materials, and the results of calculation are reported in this paper. The modeling shows that a lot of secondary minerals which contain the components of the glass could be formed due to the interaction between glass and groundwater of Beishan Wuyi well. The formation of the secondary minerals could not only decrease the concentrations of the radionuclides in the groundwater, but also fill and block the pores in the rock, and reduce the groundwater flow rate. These processes are very important to prevent the nuclides from migrating into the human’s environment. The most significant feature for the interaction between groundwater and granite from Beishan area is the precipitation of large amount of clay minerals, such as montmorillonite, smectite, nontronite, beidellite and so on, in the later stage of the reaction. All of them have very strong adsorptivity for the nuclides. So it is thought that the granite of Beishan Area is favorable to the construction of HLW repository.