Speaker
Description
The occurrence forms and migration behaviors of uranium in the environment are crucial for the environmental safety assessment around nuclear facilities. Based on the geochemical process of uranium in the environment, remediation strategies including phosphoric agents, reductive agents, as well as reductive bacteria treatment, have been proposed to immobilize uranium in the contaminated sites. The solutes migration models have been constructed to describe and predict the uranium migration ability and then evaluate the effectiveness of immobilization remediation. However, the migration distance of on-site monitoring is often greater than the predicted migration distance, studies have revealed that the colloids mediated transport contribute an important role in radionuclide migration. Uranium, on the one hand, is prone to form the intrinsic colloids under groundwater conditions due to its nucleation and crystallization process; on the other hand, it easily associates with the widely existed environmental colloids to form the pseudo colloids. The existence of colloidal stated uranium significantly affects the transport patterns and the environmental risk, which should be given critical consideration when assessing the remediation effectiveness on a uranium contaminated site. This presentation aims at the environmental risk and the immobilization effectiveness adjacent to uranium contaminated sites, the uranium transport abilities under the phosphoric or reductive media are discussed at the absence and presence of environmental colloids, the transport occurrence and mechanism of uranium are clarified with the aid of advanced spectroscopic evidences as well as theoretical calculation, the role of colloidal state uranium, including both intrinsic and pseudo uranium colloids, are identified and described. Relevant achievements provide theoretical basis and support for the reliable assessment on nuclear environmental safety around uranium contaminated sites.