Clay properties Diffusion

Three input parameters are varied to account for different kinds of generic uncertainties (1) the diffusion constant is varied to account for the uncertainty of the clay properties on the (yet unknown) location of a future repository, (2) the dissolution rate is varied to address the uncertainly due to complex interactions between the vitrified glass and the surrounding concrete, and (3) the plug composition has been varied between 0%-100% clay and 100%-0% sand since no decision on the composition has been made yet. As output, several risk related parameters are calculated the dose rate in the biosphere and radiotoxicity concentrations and -fluxes in several compartments, both for the sum of aU nucUdes and for the most relevant individual nuclides. 

Mobility of The Anion-Free Water. It is well known that water in the electrical double layer is under a field strength of 10 -10 V/cm and that the water has low dielectric constants (36). Since anion-free water is thought to be the water in the electrical double layer between the clay and the bulk solution, at high electrolyte concentrations, the double layer is compressed therefore, the water inside is likely quite immobile. At low electrolyte concentrations, the electrical double layer is more diffuse, the anion-free water is expected to be less immobile. Since the evaluation of the shaly formation properties requires the knowledge of the immobile water, experiments were conducted to find out the conditions for the anion-free water to become mobile. 

An assessment of the rates and duration of phenolic acid production from a residue is an important first step. Laboratory and field studies for assessing the dynamics of phenolic acid production must include considerations of the nature of the residue, soil properties, nutrient status of the system, microbial biomass interrelationships, temperature, moisture, residue placement in or on the soil, and other factors that relate to the field. Soil properties in the field are especially important when organic residues are incorporated. When soils are wet, such as those with more than -0.02 MPa water potential, oxygen diffusion is impeded and anaerobic conditions prevail, especially in soils that are high in clay content. Under these circumstances, microbial byproducts change dramatically and one result, for example, is an increase in the production of phenolic acids. Phenolic acid production is also affected by temperature (22) and soil fertility status (23). While the C H ratio of an organic residue may influence the rate of its decomposition and, hence, the rate of phenolic acid production, the... 

Sposito and co-workers employed a rigid framework for the clay lattice that has been used successfully to predict rf(001) layer spacing, interlayer structure, and water self-diffusion coefficients [62-80], Calculated layer spacings and thermodynamic properties, as well as interlayer water configurations and interlayer-species self-diffusion coefficients are in agreement with available experimental data. 

MD and MC simulations have provided data on layer spacings, thermodynamic properties, as well as interlayer water configurations, interlayer-species self-diffusion coefficients, and total radial distribution functions that are consistent with experimental data. Most of the clay surface is relatively... 

Manjanna, J., T. Kozaki, and S. Sato. 2009. Fe(III)-montmorillonite Basic properties and diffusion of tracers relevant to alteration of bentonite in deep geological disposal. Appl. Clay Sci. 43 208-217. 

Mass flow through a porous medium is influenced by the porosity of the medium in much the same way as diffusion is influenced by porosity. Thus, mass flow proceeds faster in a high-porosity sand than in a low-porosity clay. In addition, many of the physical properties of atmospheric air influence the aeration of soil and porous overburden by mass flow. Baver et al. (1972) estimate their contributions (Table l-III). 

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