Radionuclides interaction with solids

Lieser K. H., Radionuclides in the geosphere sources, mobility, reactions in natural waters and interactions with solids, Radiochim. Acta, 70/71 (1995) pp. 355-375. 

Mobility and transport of radionuclides in the geosphere are influenced markedly by their interaction with solids. Migration is retarded, or even stopped, if the interaction is strong, in particular if the radionuclides are incorporated into the solids. Sorption of radionuclides on solids has been investigated extensively for materials in the neighbourhood of planned high-level waste repositories. 

K. H. Lieser, Radionuclides in the Geosphere Sources, Mobility, Reactions in Natural Waters and Interactions with Solids, Radiochim. Acta 70/71, 355 (1995)... 

The radiation from radionuclides interacts with matter and causes ionization, excitation, or chemical changes. These effects are utilized in the methods of radiation detection and measurement. Among them the most commonly used effects are the ionization in gases, the interaction of radiation with semiconducting materials, the orbital electron excitation in solids and liquids, and the specific chemical reactions in sensitive emulsions. 

Interactions of Radionuclides with Solid Components of the Geosphere... 

The large number of measurements in various systems lead to the result that the interaction of radionuclides with solids is rather complex and depends on many parameters the species of the radionuclides in the solution, their properties and their dispersion, the components of the solid, the surface area of the particles, the nature of the sorption sites, the presence of organic substances and of microorganisms, and the interference or competition of other species. Therefore, an investigation of the behaviour of the radionuclides in the specific system of interest is unavoidable, if reliable information about their migration behaviour is required. 

The interaction and sorption of metal ions with metal oxide and clay surfaces has occupied the attention of chemists, soil scientists, and geochemists for decades (1-4). Transition metal oxides receiving particular emphasis have included various oxides of manganese and iron (5). Interest in sorption phenomena is promoted by the desire to better understand incorporation of metals into minerals, especially marine deposits ( ), the removal of trace metal pollutants and radionuclides from rivers and streams, via sorption and/or precipitation phenomena (1,6), and the deposition of metals on solid substrates in the preparation of catalysts (7,8). 

The groundwater transport of radionuclides through waterbearing interbed layers in the Columbia River basalt formation will be controlled by reactions of the radionuclides with groundwater and interbed solids. These interactions must be understood to predict possible migration of radionuclides from a proposed radioactive waste repository in basalt. Precipitation and sorption on interbed solids are the principle reactions that retard radionuclide movement in the interbeds. The objective of the work described herein was to determine the sorption and desorption behavior of radionuclides important to safety assessment of a high-level radioactive waste repository in Columbia River basalt. The effects of groundwater composition, redox potential, radionuclide concentration, and temperature on these reactions were determined. 

Environmental scientists such as those involved in performance assessment (e.g., for nuclear repositories) would be pleased to be able to predict the interactions of solutes (e.g., radionuclides) with backfill and geologic materials. However, in this area, which in many countries receives much public attention, even the aqueous solution equilibria for the pertaining conditions of a favored repository concept cannot be accurately described (e.g., metal ions in brine solutions, which require Pitzer formalism, or in highly alkaline backfill pore waters, which have traditionally not received much attention in aqueous solution studies because of the limitations of glass electrodes and solid phase formation). Databases for surface complexation applications are also required for many other purposes, but the major drawback of such potential databases is that no agreement exists on the actual surface complexation model to be used. This may ultimately lead to particular difficult situations whenever one of the following occur ... 

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