The Healing Process of the Joints between Buffer Material Blocks and the Influence on Solute Migration

A set of thermo-hydro-mechanical coupling control equations was established, and the healing process of the joints between Gaomiaozi bentonite (GMZ01) buffer material blocks and the influence of the joint parameters were numerically simulated. The calculations consider the effect of joints on solute migration, the permeability and thermal conductivity of the buffer material, and the evolution of the healing effect. The effects of the joint design parameters, including the type, number, width, splicing form, and average dry density of the joint, are investigated. Studies show that, under an external water head, the joints will become hydraulic priority channels due to their higher permeability, which will shorten the saturation time of the blocks. As the bentonite gradually saturates, the swelling force compresses the joint material. This action improves the overall uniformity of the buffer material and reduces the priority channel effect. Meanwhile, the final average permeability and diffusion coefficient of the buffer material are found to mainly depend on the average dry density of the buffer material. The higher the average dry density of the buffer material is, the lower the final average permeability and diffusion coefficient are, whereas the distribution of joints and the block splicing are less affected by the average dry density of the buffer material. The findings of this study can provide a reference for the design of bentonite buffer material blocks in the repository.

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Study Of Factors Affecting The Thermal Conductivity Of Iraqi Bentonite

Baghdad Science Journal ◽

10.21123/bsj.9.3.548-553 ◽

2012 ◽

Vol 9 (3) ◽

pp. 548-553

Author(s):

Baghdad Science Journal

Keyword(s):

Experimental Data ◽

Thermal Conductivity ◽

Volume Fraction ◽

Dry Density ◽

Factors Affecting ◽

Compacted Bentonite ◽

Bentonite Buffer ◽

Buffer Material ◽

Major Factors ◽

Water Contents

Thermal conductivity of compacted bentonite is one of the most important properties where this type of clay is proposed for use as a buffer material. In this study, Lee's disc method was used to measure the thermal conductivity of compacted bentonite specimens. The experimental results have been analyzed to observe the three major factors affecting the thermal conductivity of bentonite buffer material. While the clay density reaches to a target value, the measurement is taken to evaluate the thermal conductivity. By repeating this procedure, a relationship between clay dry density and thermal conductivity has been established in specimens after adjusting the water contents of the bentonite by placing its specimens in a drying oven for different periods. So relationships of thermal conductivity with each of these major factors (clay density, water content, and sand volume fraction) are established in this study. The relevance of these relationships be analyzed together using experimental data on many compacted bentonites.

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Effects of Dry Density and Water Content on Mechanical Properties of Sand-Bentonite Buffer Material

Current Geotechnical Engineering Aspects of Civil Infrastructures - Sustainable Civil Infrastructures ◽

10.1007/978-3-319-95750-0_9 ◽

2018 ◽

pp. 109-123

Author(s):

Janaka J. Kumara ◽

Takeshi Kodaka

Keyword(s):

Mechanical Properties ◽

Water Content ◽

Dry Density ◽

Bentonite Buffer ◽

Buffer Material

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Moisture Adsorption and Volume Change of Partially Saturated Bentonite Buffer Materials

MRS Proceedings ◽

10.1557/proc-294-425 ◽

1992 ◽

Vol 294 ◽

Cited By ~ 8

Author(s):

Takeshi Kanno ◽

Hisao Wakamatsu

Keyword(s):

Water Vapor ◽

Volumetric Strain ◽

Water Vapor Adsorption ◽

Dry Density ◽

Moisture Adsorption ◽

Vapor Adsorption ◽

Bentonite Buffer ◽

Buffer Material ◽

High Level ◽

Analytical Expressions

ABSTRACTWater vapor adsorption characteristics of buffer materials to be used for the geologic disposal of high-level radioactive waste have been investigated. Highly compacted blocks of Japanese Na bentonite were used as the buffer material. Initial dry density of the blocks was 1.8 g/cm3. Volume changes and water contents of the blocks in equilibrium with surrounding moist air were measured. The humidity of the surrounding air was kept constant, and the suction of the block at equilibrium has been determined by the humidity. The temperature of the surrounding air was varied between 20°C and 60°C.The volumetric strain was observed to vary approximately between −3% and 13% depending on the humidity of 0.6% to 95%. Some analytical expressions derived from these experiments on moisture adsorption are presented in this paper. Water vapor adsorption isotherm of the bentonite blocks was also obtained. The swelling pressures calculated from the analytical expressions are compared with literature data for this bentonite.

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Effective Diffusivities of Iodine, Chlorine, and Carbon in Bentonite Buffer Material

MRS Proceedings ◽

10.1557/proc-556-687 ◽

1999 ◽

Vol 556 ◽

Cited By ~ 4

Author(s):

H. Kato ◽

T. Nakazawa ◽

S. Ueta ◽

M. Muroi ◽

I. Yasutomi ◽

...

Keyword(s):

Organic Carbon ◽

Radioactive Waste ◽

Pore Water ◽

Effective Diffusivity ◽

Radioactive Waste Disposal ◽

Radioactive Isotopes ◽

Dry Density ◽

Bentonite Buffer ◽

Buffer Material ◽

Effective Diffusivities

AbstractEffective diffusivities of iodine, chlorine, and carbon in mixtures of bentonite and sand were determined by measuring the effective diffusivities of common chemical compounds labeled with radioactive isotopes of these elements. For carbon, both inorganic and organic carbon compounds were used in order to consider the variety of chemical forms of carbon possible in a radioactive waste repository. The bentonite content and dry density of the bentonite–sand mixture were varied. Two chemically different aqueous solutions, representing concrete pore water and bentonite pore water, were used to represent different conditions that could affect diffusivity in bentonite buffer material in a hypothetical radioactive waste disposal situation.The effective diffusivities of iodine, chlorine, and carbon tended to decrease with increasing bentonite content and dry density of the mixture. In the presence of simulated concrete pore water, the effective diffusivities for iodine, chlorine, and carbon in the bentonite mixtures were not higher than those obtained when simulated bentonite pore water was used. Except for some organic compounds, the measured effective diffusivities were lower than that of tritiated water under the same experimental conditions. This was attributed primarily to exclusion of anions from the bentonite pores. The effective diffusivity of carbon depended on its chemical form. The effective diffusivity of the anionic forms of organic carbon tested (carboxylic acids ) was as low as that of inorganic anionic carbon.Measured effective diffusivities were compared with those calculated using a model based on electrical double layer theory. The theory was applied to calculate distributions of electrolyte ions and diffusing ions in the bentonite pores. The calculated effective diffusivities showed good agreement with the measured values.

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