Radionuclide clays

McClellan, R. O., Barnes, J. E., Boecker, B. B., Cuddihy, R. G., Hobbs, C. H., Jones, R. K. and Redman, H. C. (1970a). Some observations on the toxicity of beta-emitting radionuclides inhaled in fused clay particles, page 197 in Fission Product Inhalation Program Annual Report 1969-1970, Report No. LF-43 (Lovelace Foundation, Albuquerque, New Mexico). 

Bors J, Dultz S, Riebe B (2000) Organophilic bentonites as adsorbents for radionuclides I. Adsorption of ionic fission products. Appl Clay Sci 16 1-13... 

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). 

Reference materials that represent the primary deep-sea and coastal depositional environments and biological materials would solve many of the problems that radiochemists face in analysis of sediments from these settings. Radiochemists require reference materials comprising the primary end member sediment and biological types (calcium carbonate, opal, and red clay from the deep-sea and carbonate-rich, silicate-rich, and clay mineral-rich sediments from coastal environments and representative biological materials). Additional sediment reference material from a river delta would be valuable to test the release of radionuclides that occurs as riverine particles contact seawater. 

Variation of Cs adsorption with depth, as a function of changes in clay content, is reported by Melkior et al. (2005) the study aimed to test the efficiency of a host rock for radionuclide confmement. Mudrock samples were collected from Callovo-Oxfordian layers in Bure (France), at depths between 22m and 78m. The total clay content increases with depth by a factor of two to three between the measured depths. Figure 8.37 depicts the of Cs as a function of its concentration in solution at equilibrium. 

Studies of the sorption of natural radionuclides from groundwater have established that minor minerals, such as clays coating the fractures in crystalline rock and Fe- and Mn-oxyhydroxides, are important sinks for radionuclides. For example, investigations carried out at the Aspo facility (Smellie Karlsson 1999) showed qualitatively that rare earth elements (REEs), Sc, Th, U, Ra, and Ba have been scavenged by Fe-oxyhydroxide and calcite precipitates,... 

Pourcelot, L. Gauthier-Lafaye, F. 1999. Hydrothermal and supergen clays of the Oklo natural reactors conditions of radionuclide release, migration and retention. Chemical Geology, 157, 155-174. 

Much stronger kinetic stabilization can be expected for processes leading to the inclusion of radionuclide ions into the colloid structure (Fig. 7, lower part). Spectroscopic indications for such processes have indeed been found again by TRLFS for the Cm(III) interaction with colloidal and particulate amorphous silica, calcite and CSH phases (Chung et al. 1998 Stumpf Fanghanel 2002 Tits et al. 2003). The incorporation of actinide ions into colloidal precursor clay phases has been recently investigated as a possible mechanism in natural... 

Bradbury Baeyens (2002a, b) provided sorption data bases for Opalinus Clay and MX-80 bentonite, respectively, based on numerous experiments with varying aqueous solution compositions. Since sorption can be influenced by the complexa-tion of radionuclides with various ligands, corrections had to be made to account for the differences in speciation between the experimental solutions and the Opalinus Clay and bentonite porewaters. For this purpose, the Nagra/PSI TDB 01 /01 was used to model the speciation of all safety-relevant radionuclides in the experimental solutions and in the Opalinus Clay and bentonite porewaters. 

Berner, U. 2002a. Project Opalinus Clay Radionuclide Concentration Limits in the Near-Field of a Repository for Spent Fuel and Vitrified High-Level Waste. Nagra Technical Report NTB 02-10, Nagra, Wettingen, Switzerland. Also issued as PSI Bericht Nr. 02-22, Paul Scherrer Institut, Villi-gen, Switzerland. 

Retention in the Backfill Material. The radionuclide holdup time in the backfill barrier for the KBS-concepts is in the order of thousands of years or less (15). Thus, only a few of the long-lived radionuclides in HLW and SUF ( °Sr, Cs and lAm) will be able to decay within the clay barrier and the more long-lived nuclides will just be delayed in their migration out into the bedrock. In the long-term time span the backfill material is of minor importance, as far as the retaining effect is concerned. 

Allard, B., Kipatsi, H. and Rydberg, J., "Sorption of Long-Lived Radionuclides on Clay and Rock". Part I, KBS TR 55, 1977 Allard, B., Kipatsi, H. and Torstenfelt, B., "Sorption of Long-Lived Radionuclides on Clay and Rock", Part II, KBS TR 98,... 

Blomqvist, G., "Leaching of French, British and Canadian Glass Containing High-level Radioactive Waste", KBS TR 08, 1977 Neretnieks, I., "Transport of Oxidants and Radionuclides Through a Clay Barrier", KBS TR 79, 1978... 

In most mathematical analyses used to establish bounds for radionuclide migration rates through the abyssal red clays, the sorption properties of the sediment are generally represented mathematically by the sorption equilibrium distribution coefficients for each of the species involved. These coefficients are usually denoted by Kp. and are defined by... 

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