Impact of Environmental Factors on the Migration of Pu, Am, Np and Tc in Geological Systems

摘要

The aim of this study is to provide geochemical data to be included in a model under construction to describe the migration of radionuclides through the geosphere. A large series of distribution coefficients was determined by batch and column experiments. The radionuclides were: Americium-241, Plutonium-238, 239 and 240, Neptunium-237 and Technetium-99. Geological materials were glauconite containing sand and materials from near Gorleben (Federal Republic of Germany). THe main variables of which the impact was studied were: pH, redox potential (Eh), salt concentration and contact time. Also the influence of textural composition, CEC, organic matter content and ionic composition of the associated ground waters on the sorption of the radionuclides was studied. From the data of the batch, column and microcosm studies it can be concluded that the migration of Pu, Am, Np and Tc will be strongly delayed due to adsorption of these nuclides on geological material. In anaerobic systems at low pH values Pu and Am will migrate faster than Np. For aerobic conditions, but also for anaerobic conditions at high pH, Np will migrate faster than Pu and Am. Tc may migrate in aerobic systems; it will become less mobile if reduction occurs. As far as modelling is concerned, without a rather detailed knowledge of the local redox potential and pH, a fair estimate of the migration is not possible. (ERA citation 13:009504)