Prediction for swelling characteristics of compacted bentonite

1996 ◽  
Vol 33 (1) ◽  
pp. 11-22 ◽  
Author(s):  
Hideo Komine ◽  
Nobuhide Ogata
Keyword(s):  
Prediction Method ◽  
Swelling Pressure ◽  
Ion Concentration ◽  
Diffuse Double Layer ◽  
Compacted Bentonite ◽  
Laboratory Test Results ◽  
Swelling Characteristics ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Waste Repositories

Compacted bentonites are attracting greater attention as back-filling (buffer) materials for high-level nuclear waste repositories. For this purpose, it is very important to quantitatively evaluate the swelling characteristics of compacted bentonite. New equations for evaluating the relationship between the swelling deformation of compacted bentonite and the distance between two montmorillonite layers are derived. New equations for evaluating the ion concentration of pore water and the specific surface of bentonite, which significantly influence the swelling characteristics of compacted bentonite, are proposed. Furthermore, a prediction method for the swelling characteristics of compacted bentonite is presented by combining the new equations with the well-known theorectical equations of repulsive and attractive forces between two montmorillonite layers. The applicability of this method was investigated by comparing the predicted results with laboratory test results on the swelling deformation and swelling pressure of compacted bentonites. Key words: bentonite, diffuse double-layer theory, van der Waals force, nuclear wastes disposal, swelling deformation, swelling pressure.

New equations for swelling characteristics of bentonite-based buffer materials

2003 ◽  
Vol 40 (2) ◽  
pp. 460-475 ◽  
Author(s):  
Hideo Komine ◽  
Nobuhide Ogata
Keyword(s):  
Double Layer ◽  
Nuclear Waste ◽  
Van Der Waals ◽  
Swelling Pressure ◽  
Van Der Waals Force ◽  
Diffuse Double Layer ◽  
Mass Ratio ◽  
Compacted Bentonite ◽  
Buffer Material ◽  
Swelling Characteristics

Compacted bentonite and sand–bentonite mixtures are attracting greater attention as buffer material for repositories of high-level nuclear waste. This buffer material is expected to fill up the space between the canisters containing the waste and the surrounding ground by swelling. To produce the specifications, such as dry density, sand–bentonite mass ratio, and dimensions, of the buffer material, the swelling characteristics of compacted bentonite and sand–bentonite mixtures must be evaluated quantitatively. New equations for evaluating the swelling behavior of compacted bentonite and sand–bentonite mixtures are presented that can accommodate the influences of the sand–bentonite mass ratio and the exchangeable-cation composition of bentonite. The new method for predicting swelling characteristics is presented by combining the new equations with the theoretical equations of the Gouy–Chapman diffuse double layer theory and of the van der Waals force, which can evaluate the repulsive and attractive forces of montmorillonite mineral (i.e., the swelling clay mineral in bentonite). Furthermore, the applicability of the new prediction method has been confirmed by comparing the predicted results with laboratory test results on the swelling deformation and swelling pressure of compacted bentonites and sand–bentonite mixtures.Key words: bentonite, diffuse double layer theory, van der Waals force, nuclear waste disposal, swelling deformation, swelling pressure.

Experimental study on swelling characteristics of compacted bentonite

1994 ◽  
Vol 31 (4) ◽  
pp. 478-490 ◽  
Author(s):  
Hideo Komine ◽  
Nobuhide Ogata
Keyword(s):  
Water Content ◽  
Nuclear Waste ◽  
Volumetric Strain ◽  
Swelling Pressure ◽  
Dry Density ◽  
Initial Water Content ◽  
Initial Water ◽  
Compacted Bentonite ◽  
Swelling Characteristics ◽  
High Level

Compacted bentonites are attracting greater attention as back-filling (buffer) materials for repositories of high-level nuclear waste. However, since there are few studies about the swelling characteristics of compacted bentonites, it is first necessary to clarify the fundamental swelling characteristics in detail. For this purpose, various laboratory tests on the swelling deformation and swelling pressure of compacted bentonites were performed and the results analyzed. The following conclusions were drawn from the study. (i) The curve of swelling deformation versus time is strongly dependent on the initial dry density, vertical pressure, and initial water content. The maximum swelling deformation, however, is almost independent of initial water content, and the maximum swelling deformation increases in proportion to the initial dry density, (ii) The maximum swelling pressure increases exponentially with increasing initial dry density, whereas the maximum swelling pressure is almost independent of initial water content. (iii) The swelling mechanism of compacted bentonite was considered on the basis of the swelling behavior of swelling clay particles such as montmorillonite. Furthermore, a model of the swelling characteristics and a new parameter (swelling volumetric strain of montmorillonite), which were able to evaluate the swelling characteristics of compacted bentonite, were proposed. Key words : bentonite, laboratory test, nuclear waste disposal, swelling deformation, swelling pressure.

Some Aspects on the Use of Iron Canisters for HLW

1985 ◽  
Vol 50 ◽  
Author(s):  
Ivars Neretnieks
Keyword(s):  
Bentonite Clay ◽  
Potential Effect ◽  
Hydrogen Gas ◽  
Lithostatic Pressure ◽  
Equilibrium Pressure ◽  
Capillary Suction ◽  
Compacted Bentonite ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Rock Overburden

AbstractIron canisters for high level nuclear waste embedded in compacted bentonite in deep geologic repositories will corrode forming hydrogen gas. The equilibrium pressure (when corrosion would stop) has been estimated to be between 500 and 1000 atm. under repository conditions. As this is much higher than the lithostatic pressure (weight of rock overburden) the gas must be allowed to escape before it disrupts the repository. Escape by diffusion alone is not sufficient but recent experiments have demonstrated that the larger pores in the bentonite are blown free of water and let the gas escape before excessive pressures build up.The potential effect of a capillary breaking layer (CBL) has been explored. A fine layer nearest the canister (e.q. quartz sand) would have much lower capillary suction pressures than the bentonite clay and would keep the water out as long as there is sufficient overpressure. As long as the CBL is void of liquid water no radionuclides can escape, even if the canister is penetrated.

scholarly journals Towards higher temperatures in nuclear waste repositories

2020 ◽  
Vol 205 ◽  
pp. 01001
Author(s):  
Antonio Gens ◽  
Ramon B. de Vasconcelos ◽  
Sebastià Olivella
Keyword(s):  
Nuclear Waste ◽  
Large Scale ◽  
Maximum Temperature ◽  
Spent Fuel ◽  
Thermally Induced ◽  
Large Scale Field ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Host Rocks ◽  
Waste Repositories

Recently, there is a tendency to explore the possibility of increasing the maximum design temperature in deep geological repositories for high-level nuclear waste and spent fuel. In the paper, a number of issues related to the use of higher temperatures are reviewed. Both bentonite barriers and argillaceous host rocks are addressed. An application involving the modelling of a large-scale field test conducted at a maximum temperature of 140ºC is presented. It is shown that currently available theoretical formulations and computer codes are capable to deal with temperatures above 100ºC and to reproduce satisfactorily the thermally-induced overpressures in the rock.

Modeling Hydraulic Conductivity and Swelling Pressure of Several Kinds of Bentonites Affected by Salinity of Water

2010 ◽  
Author(s):  
Yukihisa Tanaka ◽  
Takuma Hasegawa ◽  
Kunihiko Nakamura
Keyword(s):  
Hydraulic Conductivity ◽  
Radioactive Waste ◽  
Ground Water ◽  
Quantitative Evaluation ◽  
Coastal Area ◽  
Evaluation Method ◽  
Saline Water ◽  
Swelling Pressure ◽  
Compacted Bentonite ◽  
Swelling Characteristics

In case of construction of repository for radioactive waste near the coastal area, the effect of salinity of water on hydraulic conductivity as well as swelling pressure of bentonite as an engineered barrier should be considered because it is known that the hydraulic conductivity of bentonite increases and swelling pressure decreases with increasing salinity of water. Though the effect of salinity of water on hydraulic conductivity and swelling pressure of bentonite has been investigated experimentally, it is necessary to elucidate and to model the mechanism of the phenomenon because various kinds of bentonites may possibly be placed in various salinities of ground water. Thus, in this study, a model for evaluating hydraulic conductivity as well as swelling pressure of compacted bentonite is proposed considering the effect of salinity of water as follows: a) Change in number of flakes of a stack of montmorillonite because of cohesion. b) Change in viscosity of water in interlayer between flakes of montmorillonite. Quantitative evaluation method for hydraulic conductivity and swelling characteristics of several kinds of bentonites under saline water is proposed based on the model mentioned above.

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