The uncertainties associated with the application of through-diffusion, the steady-state method: a case study of strontium diffusion
Published:January 01, 2014
J. Gondolli, P. Večerník, 2014. "The uncertainties associated with the application of through-diffusion, the steady-state method: a case study of strontium diffusion", Clays in Natural and Engineered Barriers for Radioactive Waste Confinement, S. Norris, J. Bruno, M. Cathelineau, P. Delage, C. Fairhurst, E. C. Gaucher, E. H. Höhn, A. Kalinichev, P. Lalieux, P. Sellin
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In this study, the uncertainties associated with through-diffusion, the steady-state method used for determination of the pore diffusion coefficient (Dp), were analysed and evaluated. The diffusion of strontium through the sample of compacted bentonite was studied to evaluate various sources of uncertainties and compare their contribution with uncertainty of Dp. Different diffusion experiment arrangements were used to test the effect of solution accessibility to the filter membranes. Three main general factors influencing the uncertainty of Dp at given conditions were identified: (a) the compacted sample preparation and its physical properties; (b) the properties of the diffusion cell; and (c) the strontium concentration analyses. Some of the identified sources can be treated as fixed with limited extent (e.g. the deformation of components of the diffusion cell), but some sources must be treated as variable with wide extent depending on the experimental conditions (e.g. the physical properties of the compacted bentonite sample – moisture, density, porosity). The variable uncertainty sources have to be taken into account, especially in repeatability and reproducibility tests. It was concluded that each of the diffusion cells with compacted bentonite sample represents a unique diffusion system. It is preferable to present the results of diffusion experiments as a range of values rather than as one average value with an uncertainty.
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Clays in Natural and Engineered Barriers for Radioactive Waste Confinement
This Special Publication contains 43 scientific studies presented at the 5th conference on ‘Clays in natural and engineered barriers for radioactive waste confinement’ held in Montpellier, France in 2012. The conference and this resulting volume cover all the aspects of clay characterization and behaviour considered at various temporal and spatial scales relevant to the confinement of radionuclides in clay, from basic phenomenological process descriptions to the global understanding of performance and safety at repository and geological scales. Special emphasis has been given to the modelling of processes occurring at the mineralogical level within the clay barriers.
The papers in this Special Publication consider research into argillaceous media under the following topic areas: large-scale geological characterization; clay-based concept/large-scale experiments; hydrodynamical modelling; geochemistry; geomechanics; mass transfer/gas transfer; mass transfer mechanisms.
The collection of different topics presented in this Special Publication demonstrates the diversity of geological repository research.