HTO Diffusion in Oxfordian Limestone and Callovo-Oxfordian Argillite Formations

2004 ◽  
Vol 824 ◽  
Author(s):  
M. Descostes ◽  
V. Blin ◽  
B. Grenut ◽  
P. Meier ◽  
E. Tevissen
Keyword(s):  
Pore Water ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Effective Diffusion Coefficients ◽  
Rock Laboratory ◽  
Diffusion Technique ◽  
Through Diffusion ◽  
Two Parameters ◽  
Geological Formations

AbstractDiffusion coefficients and accessible porosities for HTO were measured on 30 samples from the Andra Underground Rock Laboratory in Meuse/Haute-Marne (France) using the through diffusion technique. Two distinct geological formations were studied: Oxfordian limestone and Callovo-oxfordian argillite between 166 and 477 m depth. The experiences were carried out with synthetic pore-water from each formation. The measured values of the effective diffusion coefficients (De) are ranging from 2.6× 10-12 to 12.4 × 10-11 m2 s-1 while accessible porosities (ε) are between 2.4 and 24%. Good correlations are found between these two parameters.

scholarly journals Measurement on Diffusion Coefficients and Isotope Fractionation Factors by a Through-Diffusion Experiment

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 208
Author(s):  
Takuma Hasegawa ◽  
Kotaro Nakata ◽  
Rhys Gwynne
Keyword(s):  
Groundwater Flow ◽  
Diffusion Coefficients ◽  
Isotope Fractionation ◽  
Free Water ◽  
Effective Porosity ◽  
Diffusion Experiment ◽  
Fractionation Factor ◽  
Through Diffusion ◽  
Geological Formations ◽  
Fractionation Factors

For radioactive waste disposal, it is important that local groundwater flow is slow as groundwater flow is the main transport medium for radioactive nuclides in geological formations. When the groundwater flow is very slow, diffusion is the dominant transport mechanism (diffusion-dominant domain). Key pieces of evidence indicating a diffusion-dominant domain are the separation of components and the fractionation of isotopes by diffusion. To prove this, it is necessary to investigate the different diffusion coefficients for each component and the related stable isotope fractionation factors. Thus, in this study, through-diffusion and effective-porosity experiments were conducted on selected artificial materials and natural rocks. We also undertook measurements relating to the isotope fractionation factors of Cl and Br isotopes for natural samples. For natural rock samples, the diffusion coefficients of water isotopes (HDO and H218O) were three to four times higher than those of monovalent anions (Cl−, Br- and NO3−), and the isotope fractionation factor of 37Cl (1.0017–1.0021) was slightly higher than that of free water. It was experimentally confirmed that the isotope fractionation factor of 81Br was approximately 1.0007–1.0010, which is equivalent to that of free water. The enrichment factor of 81Br was almost half that of 37Cl. The effective porosity ratios of HDO and Cl were slightly different, but the difference was not significant compared to the ratio of their diffusion coefficients. As a result, component separation was dominated by diffusion. For artificial samples, the diffusion coefficients and effective porosities of HDO and Cl were almost the same; it was thus difficult to assess the component separation by diffusion. However, isotope fractionation of Cl and Br was confirmed using a through-diffusion experiment. The results show that HDO and Cl separation and isotope fractionation of Cl and Br can be expected in diffusion-dominant domains in geological formations.

Effective Diffusion Coefficients and Thermal Stability of the Structure of Metallic Glass Fe48Co32P14B6

2020 ◽  
Vol 62 (12) ◽  
pp. 2258-2265 ◽  
Author(s):  
S. V. Vasiliev ◽  
V. I. Parfenii ◽  
E. A. Pershina ◽  
A. S. Aronin ◽  
O. V. Kovalenko ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Metallic Glass ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Effective Diffusion Coefficients ◽  
Thermal Stability Of

scholarly journals Modeling and thermodynamic properties of ‘bacaba’ pulp drying

2019 ◽  
Vol 23 (9) ◽  
pp. 702-708 ◽  
Author(s):  
Maria F. de Morais ◽  
José R. O. dos Santos ◽  
Marisângela P. dos Santos ◽  
Dyego da C. Santos ◽  
Tiago N. da Costa ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermodynamic Properties ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Thermal Conditions ◽  
Drying Process ◽  
Experimental Conditions ◽  
Effective Diffusion Coefficients ◽  
Drying Rates ◽  
Increasing Temperature

ABSTRACT This study aimed to dry ‘bacaba’ (Oenocarpus bacaba Mart.) pulp under different thermal conditions, fit different mathematical models to the dehydration curves, and calculate the diffusion coefficients, activation energy and thermodynamic properties of the process. ‘Bacaba’ fruits were meshed to obtain the pulp, which was dried at temperatures of 40, 50 and 60 °C and with thickness of 1.0 cm. Increase in drying temperature reduced the dehydration times, as well as the equilibrium moisture contents, and drying rates of 0.65, 1.04 and 1.25 kg kg min-1 were recorded at the beginning of the process for temperatures of 40, 50 and 60 °C, respectively. The Midilli’s equation was selected as the most appropriate to predict the drying phenomenon, showing the highest R2, lowest values of mean square deviation (MSD) and χ2 under most thermal conditions, and random distribution of residuals under all experimental conditions. The effective diffusion coefficients increased with increasing temperature, with magnitudes of the order of 10-9 m2 s-1, being satisfactorily described by the Arrhenius equation, which showed activation energy (Ea) of 37.01 kJ mol-1. The drying process was characterized as endergonic, in which enthalpy (ΔH) and entropy (ΔS) reduced with the increment of temperature, while Gibbs free energy (ΔG) was increased.

Measurement of effective diffusion coefficients in dairy powders by confocal microscopy and sorption kinetic profiles

2019 ◽  
Vol 20 ◽  
pp. 100108 ◽  
Author(s):  
Valentyn Maidannyk ◽  
Eva Lutjes ◽  
Sharon Montgomery ◽  
Noel McCarthy ◽  
Mark A.E. Auty
Keyword(s):  
Confocal Microscopy ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Sorption Kinetic ◽  
Effective Diffusion Coefficients ◽  
Dairy Powders
Sign in / Sign up

Export Citation Format

Share Document