Direct Determination of Transport Parameters in Repository Materials

1992 ◽  
Vol 294 ◽  
Author(s):  
J. L. Conca ◽  
M.J. Apted ◽  
R.C. Arthur
Keyword(s):  
Diffusion Coefficients ◽  
Direct Determination ◽  
Advective Transport ◽  
Transport Parameters ◽  
Centripetal Acceleration ◽  
Compacted Bentonite ◽  
Diffusion Limited ◽  
Gradient Measurements ◽  
Time Required ◽  
Host Rocks

ABSTRACTA new flow technology has been developed that significantly decreases the time required to obtain transport data on saturated and unsaturated porous/fractured media. This technique is based on open-flow centrifugation and was developed to measure steady-state transport properties in most geologic materials within a matter of hours. Centripetal acceleration does not induce artificial effects in samples i.e., fracturing, collapse of interlayer structures, structural dewatering, compaction, chemical changes, etc., that occur with high-pressure methods. Using this technique, hydraulic conductivities (K) and diffusion coefficients (D) for compacted bentonite and four host rocks have been measured and re-interpreted. Based on these new data, K for compacted bentonite is less than 10−14 m/s, a factor of 1000 lower than previous pressure-gradient measurements, providing further assurance that radionuclide transport through bentonite backfill will be diffusion limited. Measured K for mudstone (1.8 × 10−12 m/s) indicates diffusion-limited far-field transport, while advective transport should occur for granite, basalt, and tuff, with expected matrix diffusion coefficients (correlated to measured D values) of 8.3 × 10−13 and 2.5 × 10−12 m2/s for fractured granite and basalt, respectively.

Using dual‐domain advective‐transport simulation to reconcile multiple‐tracer ages and estimate dual‐porosity transport parameters

2017 ◽  
Vol 53 (6) ◽  
pp. 5002-5016 ◽  
Author(s):  
Ward E. Sanford ◽  
L. Niel Plummer ◽  
Gerolamo Casile ◽  
Ed Busenberg ◽  
David L. Nelms ◽  
...  
Keyword(s):  
Dual Porosity ◽  
Advective Transport ◽  
Transport Parameters ◽  
Transport Simulation ◽  
Dual Domain

scholarly journals Highly Permeable Matrimid®/PIM-EA(H2)-TB Blend Membrane for Gas Separation

Polymers ◽  
2018 ◽  
Vol 11 (1) ◽  
pp. 46 ◽  
Author(s):  
Elisa Esposito ◽  
Irene Mazzei ◽  
Marcello Monteleone ◽  
Alessio Fuoco ◽  
Mariolino Carta ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Gas Transport ◽  
Gas Permeability ◽  
Time Lag ◽  
Gas Diffusion ◽  
Gas Permeation ◽  
Spectrometric Analysis ◽  
Competitive Sorption ◽  
Transport Parameters ◽  
Mixed Gas

The effect on the gas transport properties of Matrimid®5218 of blending with the polymer of intrinsic microporosity PIM-EA(H2)-TB was studied by pure and mixed gas permeation measurements. Membranes of the two neat polymers and their 50/50 wt % blend were prepared by solution casting from a dilute solution in dichloromethane. The pure gas permeability and diffusion coefficients of H2, He, O2, N2, CO2 and CH4 were determined by the time lag method in a traditional fixed volume gas permeation setup. Mixed gas permeability measurements with a 35/65 vol % CO2/CH4 mixture and a 15/85 vol % CO2/N2 mixture were performed on a novel variable volume setup with on-line mass spectrometric analysis of the permeate composition, with the unique feature that it is also able to determine the mixed gas diffusion coefficients. It was found that the permeability of Matrimid increased approximately 20-fold with the addition of 50 wt % PIM-EA(H2)-TB. Mixed gas permeation measurements showed a slightly stronger pressure dependence for selectivity of separation of the CO2/CH4 mixture as compared to the CO2/N2 mixture, particularly for both the blended membrane and the pure PIM. The mixed gas selectivity was slightly higher than for pure gases, and although N2 and CH4 diffusion coefficients strongly increase in the presence of CO2, their solubility is dramatically reduced as a result of competitive sorption. A full analysis is provided of the difference between the pure and mixed gas transport parameters of PIM-EA(H2)-TB, Matrimid®5218 and their 50:50 wt % blend, including unique mixed gas diffusion coefficients.

Measurement of resistance of barriers to solute transport in vivo in rat jejunum

1986 ◽  
Vol 250 (6) ◽  
pp. G727-G735 ◽  
Author(s):  
H. Westergaard ◽  
K. H. Holtermuller ◽  
J. M. Dietschy
Keyword(s):  
Glucose Transport ◽  
Diffusion Barrier ◽  
Saturated Fatty Acids ◽  
Water Layer ◽  
Rat Jejunum ◽  
Transport Parameters ◽  
Live Animal ◽  
Diffusion Limited ◽  
Barrier Resistance

Assessment of intestinal absorptive function requires techniques for correcting transport constants for diffusion barrier resistance. These studies were done to develop such techniques for use in vivo. In one method the functional thickness of the unstirred water layer (d) in rat jejunum was quantitated electrically, and its minimal surface area (Sw) was measured directly. From these values the diffusion barrier resistance (d/Sw) decreased from 0.041 to 0.022 as the perfusion rate of the intestine was increased from 1.5 to 15 ml/min. In the second method apparent passive permeability coefficients (*P) were measured for a series of saturated fatty acids, and these increased with chain length. However, at the longest chain lengths tested, *P became proportional to their free diffusion coefficients, indicating that uptake was limited by the rate of diffusion up to the microvillus surface. From the rates of uptake of such diffusion-limited probes, the diffusion barrier resistance was again calculated and found to decrease from 0.041 to 0.022 as the rate of perfusion was increased from 1.5 to 15 ml/min. Over this same range of perfusion rates, the apparent Michaelis constant (*Km) for D-glucose transport decreased from 18.2 to 10.0 mM. Using either set of resistance terms and these apparent Km values, the true Km value for glucose transport in vivo was found to equal 0.8 mM when the barrier resistance was extrapolated to zero. Thus these data indicate that diffusion-limited probes can be utilized to measure unstirred layer resistance in the intestine of a live animal so that absolute transport parameters can be determined in vivo in experimental animals and, presumably, in humans.

Computer Aided Identification of the Moisture Transport Parameters in Spruce Wood

Holzforschung ◽  
2003 ◽  
Vol 57 (5) ◽  
pp. 533-538 ◽  
Author(s):  
P. Koc ◽  
M. Houka ◽  
B. Štok
Keyword(s):  
Inverse Problem ◽  
Moisture Content ◽  
Diffusion Coefficients ◽  
Moisture Diffusion ◽  
Transport Parameters ◽  
Moisture Flow ◽  
Identification Method ◽  
Three Samples ◽  
Computer Aided

Summary An inverse identification method for characterization of wood sorptive properties is presented. The method relies on a computer simulation of a real experiment, in our case a desorption experiment, where spruce heartwood samples were dried from 27% to 8% moisture content. Three samples, distinguished by the respective moisture flow pattern through the specimen, were investigated. A computer aided material characterization using the so-called inverse problem identification method was performed on the measurements. The solution of the specified inverse problem enabled us to estimate the moisture diffusion coefficients of wood and to determine the moisture content field in the sample simultaneously. The method is first verified on two simple cases of uniaxial moisture flow, and then is used to characterize the diffusion coefficients on a biaxial moisture flow sample. In the latter case some salient features of the proposed method are exhibited.

Rapid and Direct Determination of Diffusion Coefficients Using Microelectrode Arrays

2016 ◽  
Vol 163 (8) ◽  
pp. H672-H678 ◽  
Author(s):  
Jonathan Moldenhauer ◽  
Madeline Meier ◽  
David W. Paul
Keyword(s):  
Diffusion Coefficients ◽  
Microelectrode Arrays ◽  
Direct Determination

Distribution Coefficients and Apparent Diffusion Coefficients of Cesium in Compacted Bentonites

1999 ◽  
Vol 556 ◽  
Author(s):  
Akiko Okamoto ◽  
Kazuya Idemitsu ◽  
Hirotaka Furuya ◽  
Yaohiro Inagaki ◽  
Tatsumi Arima
Keyword(s):  
Diffusion Coefficients ◽  
Distribution Coefficients ◽  
Dry Density ◽  
Apparent Diffusion Coefficients ◽  
Compacted Bentonite ◽  
Apparent Diffusion ◽  
Tracer Solution ◽  
Cesium Concentration ◽  
Penetration Profile ◽  
Very High

AbstractDistribution coefficients and apparent diffusion coefficients of cesium in some compacted bentonites were determined by the penetration profile method. Cylindrical compacted bentonites with the dry density of 0.8 to 1.6 Mg/m3 were contacted with tracer solutions containing 1000, 100 or 10 ppm of cesium. The apparent diffusion coefficients were obtained from the concentration profiles of cesium in compacted bentonites. The distribution coefficients were obtained concurrently by dividing the intercepts of the profiles by the concentration of the tracer solution. The apparent diffusion coefficients of cesium in compacted bentonite were obtained in the range of 0.42 to 9.6· 10−12 m2/s. The apparent diffusion coefficients in the compacted bentonite contacted with three different concentrations of cesium tended to decrease with increasing dry density of the specimen; but, they had no dependence on cesium concentration within a factor of 3 at the same dry density. The distribution coefficient of cesium for the specimens contacted with three different concentrations of cesium were obtained in the range of 0.3 to 90 L/kg and had little dependence on dry density. The distribution coefficients obtained in the compacted bentonites were dependent on pH of the solution rather than concentration of cesium. These distribution coefficients obtained in the compacted bentonites were 10 to 1000 times smaller than those obtained by batch experiments. The data suggest that not all sorption sites for cesium are available in highly compacted bentonite. It is necessary to consider surface diffusion as a significant migration mechanism of cesium through the compacted bentonites at very high pH condition such as 12.

Thermal Analysis of Options for Spent Fuel Disposal in Switzerland

1996 ◽  
Vol 465 ◽  
Author(s):  
Tetsuo Sasaki ◽  
Kenichi Ando ◽  
Hideki Kaw Amura ◽  
Jürg W. Schneider ◽  
Ian G. McKinley
Keyword(s):  
Thermal Analysis ◽  
Basic Concept ◽  
Crystalline Basement ◽  
Opalinus Clay ◽  
High Level Waste ◽  
Spent Fuel ◽  
Compacted Bentonite ◽  
High Level ◽  
Host Rocks

ABSTRACTIn parallel to studies of disposal of vitrified high-level waste from reprocessing, projects have been initiated to examine options for direct disposal of spent fuel in Switzerland. The basic concept involves in-tunnel emplacement of encapsulated spent fuel in a deep repository which is backfilled with compacted bentonite. Two possible host rocks are considered - crystalline basement and Opalinus Clay. This paper reports the results of a thermal analysis which was carried out to evaluate constraints on repository layout set by the desire to limit temperatures experienced by the bentonite backfill.

Some Methodological Modifications of Determination of Diffusion Coefficients in Compacted Bentonite

2006 ◽  
Vol 932 ◽  
Author(s):  
Dušan Vopálka ◽  
Helena Filipská ◽  
Antonín Vokál
Keyword(s):  
Diffusion Coefficients ◽  
Effective Porosity ◽  
Diffusion Method ◽  
Dry Density ◽  
Diffusion Cell ◽  
Compacted Bentonite ◽  
Method Of Evaluation ◽  
Exclusion Effect ◽  
Positively Charged

ABSTRACTThe results of 3H, 36Cl and 137Cs diffusion experiments through compacted bentonite using a new design of diffusion cell and a new methodology of diffusion coefficients evaluation are presented. The diffusion cell was made from the stainless steel and enables to connect it directly to the input and/or output reservoirs without any tubing. The evaluation of diffusion coefficients utilizes a compartmental model developed in the environment of the GoldSim transport code. It enables to determine diffusion coefficients for various types of boundary conditions, including also input and output filters. The influence of the diffusion through filters on the determined values of both effective (De) and apparent (Da) diffusion coefficients was numerically demonstrated for the through diffusion method. This effect is most important for Da, the value of which would be underestimated using standard ways of evaluation for neutral and positively charged species, mainly in the case of high effective porosity.The comparison of standard and the newly developed method of evaluation of diffusion coefficients showed a significant influence of diffusion in filters for HTO. Contrary to the standard method of evaluation, the evaluation taking into account filters showed here no difference between total and effective porosity. The effect of filter resistance was negligible for Cl-, especially at high dry density of compacted bentonite, due to the anion exclusion effect. The numerical model developed enabled to determine Da values of Cs+ from the concentration change in the inlet reservoir.

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