Activation energy of diffusivities for deuterated water in compacted sodium-bentonite; Through-diffusion experiment and molecular dynamics simulation

Suzuki, Satoru; Sato, Haruo; Ishidera, Takamitsu; Fujii, Naoki*; Kawamura, Katsuyuki*

JNC TN8400 2001-031, 44 Pages, 2002/05

JNC-TN8400-2001-031.pdf:1.58MB

In order to quantify effect of temperature on diffusivity of deuterated water (HDO) in compacted sodium-bentonite, through-diffusion experiments were conducted at elevated tempemture from 298 to 333 K. Kunipia F (Na-montmorillonite content 98 wt. %; Kunimine Industly Co.) was compacted to a dry density of 0.9 and l.35 Mg/m. Since smectite flakes were perpendicularly oriented to a direction of compaction, anisotropy of diffusivity was investigated parallel and normal to the preferred orientation of smectite. Effective diffusion coeficient D of HDO was larger for a diffusional direction parallel to the preferred orientation than normal to that for both dry densities. These results well agreed to the previously reported ones for tritiated water. Activation energies of D in compacted bentonite increased with increasing dry density in the range of 19 - 25 kJ/mol which was slightly larger than that in bulk water (18 kJ/mol). This relationship can be considered to be due to both the pore structure development and high activation energy of water (18-23 kJ/mol) in the vicinity of smectite surface (within 2 nm) on the basis of molecular dynamics simulations.

A Development of simulation and analytical program for through-diffusion experiments for a single layer of diffusion media

Sato, Haruo

JNC TN8410 2001-003, 40 Pages, 2001/01

JNC-TN8410-2001-003.pdf:1.13MB

A program (TDROCK1.FOR) for simulation and analysis of through-diffusion experiments for a single layer of diffusion media was developed. This program was made by Pro-Fortran language, which was suitable for scientific and technical calculations, and relatively easy explicit difference method was adopted for an analysis. In the analysis, solute concentration in the tracer cell as a function of time that we could not treat to date can be input and the decrease in the solute concentration as a function of time by diffusion from the tracer cell to the measurement cell, the solute concentration distribution in the porewater of diffusion media and the solute concentration in the measurement cell as a function of time can be calculated. In addition, solution volume in both cells and diameter and thickness of the diffusion media are also variable as an input condition. This simulation program could well explain measured result by simulating solute concentration in the measurement cell as a function of time for case which apparent and effective diffusion coefficients were already known. Based on this, the availability and applicability of this program to actual analysis and simulation were confirmed. This report describes the theoretical treatment for the through-diffusion experiments for a single layer of diffusion media, analytical model, an example of source program and the manual.

A Study on Pore Structure of Compacted Bentonite (Kunigel-V1)

Sato, Haruo

JNC TN8400 99-064, 22 Pages, 1999/10

JNC-TN8400-99-064.pdf:1.45MB

Four kinds of diffusion experiments; (1)through-diffusion(T-D) experiments for compaction direction dependency, (2)in-diffusion(I-D) experiments for composition dependency of silica sand in bentonite, (3)I-D experiments for initial bentonite gain size dependency, and (4)I-D experiments for the restoration property of an artificial single fracture in compacted bentonite, were carried out using tritiated water which is a non-sorbing nuclide to evaluate the effect of pore structural factors for eompacted bentonite on diffudion. For(1), effective diffusivities (De) in Na-bentonites, Kunigel-V1 and Kunipia-F were measured for 1.0 and 1.5 Mgm. For(2), apparent diffusivities (Da) in Kunigel-V1 were measured for 0.8, 1.4 and 1.8 Mgm with silica sand of 30 and 50 wt%. For(3), Da values for 0.8, 1.4 and 1.8 Mgm were measured for a granulated Na-bentonite, OT-9607 which grain-size distribution is in a rang between 0.1 and 5 mm. For (4), Da values in Kunigel-V1 which a single fracture was artificially reproduced and was immersed in distilled water for 7 or 28 days for the restoration of the fracture, were measured for 1.8 Mgm. Although De values in Kunigel-V1 were approximately the same for both compacted directions over the density, De values for perpendicular direction to compacted direction were higher than those for the same direction as compacted direction in Kunipia-F. For composition dependency of silica sand in bentonite, no significant effect of the mixure of silica sand in bentonite on Da was found. For initial bentonite grain size dependency, Da values obtained for OT-960 were approximately the same as those for Kunigel-V1 and no effect of initial grain size of bentonite on diffusion was found. For the restoration property of a single fracture in compacted bentonite, no restoration period dependency on Da was found. Based on this, it may be said that diffusion of nuclides in compacted bentonite, ...

Ion mobility parameter of crystalline rocks in intact part

Fukuda, Kenji; Ozaki, Yusuke; Murakami, Hiroaki; Itai, Kaori*; Ishibashi, Masayuki; Sasao, Eiji

no journal, , 

Matrix diffusion is one of the important for evaluating solute transport in crystalline rock. In this study, effective diffusion coefficient, porosity, and resistivity of crystalline rock were measured. There was a positive correlation between the formation factor calculated from the resistivity measurement and the effective diffusion coefficient calculated from the transmission diffusion test. Therefore, the effective diffusion coefficient can be estimated from the resistivity measurement of crystalline rock.