scholarly journals EVALUATING INFLUENCE OF CEMENTATION ON SWELLING PROPERTIES OF BENTONITE BUFFER MATERIAL BASED ON THE RESULTS OF BENTONITE ORES

2020 ◽  
Vol 76 (3) ◽  
pp. 295-305
Author(s):  
Daichi ITO ◽  
Hideo KOMINE
Keyword(s):  
Swelling Properties ◽  
Bentonite Buffer ◽  
Buffer Material

scholarly journals Experimental study on effect by cementation on self-sealing capability of bentonite buffer material

2020 ◽  
Vol 205 ◽  
pp. 10004
Author(s):  
Daichi Ito ◽  
Hideo Komine ◽  
Hailong Wang
Keyword(s):  
High Pressures ◽  
Swelling Pressure ◽  
Swelling Properties ◽  
Bentonite Buffer ◽  
Waste Container ◽  
Buffer Material ◽  
The Difference ◽  
Property Changes ◽  
High Level

In Japanese project for disposal of high-level radioactive waste, the self-sealing capability of bentonite buffer material, which results from the swelling deformation to fill the gaps between waste container and wall of disposal pit, must be retained thousands of years. However, because of the effect of high pressures, occurrence of cementation and property changes of the buffer material are a concern. Few studies had examined cementation effects because of the difficulties for simulating long-term alteration process experimentally. In this paper, swelling properties of consolidated buffer are regarded as similar as those of naturally consolidated bentonite ore. Therefore, three kinds of bentonite ores were used for experiments to elucidate influences of cementation on self-sealing capabilities. Undisturbed and reconstituted specimens were prepared to assess their swelling pressures after filling a preset gap in a swelling pressure apparatus. Results show that for Japanese ores, the swelling pressure of undisturbed specimens is about half that of reconstituted specimens. For American and Chinese ores, the difference of swelling pressure is greater when the preset gap is smaller. Results imply that effects of cementation on self-sealing capability are smaller when swelling deformation is allowed.

Coupling Swelling and Water Retention Processes in Compacted Bentonite

2011 ◽  
Vol 6 (1) ◽  
Author(s):  
Antti Lempinen
Keyword(s):  
Water Retention ◽  
Spent Nuclear Fuel ◽  
Effective Strain ◽  
Swelling Pressure ◽  
Model Parameters ◽  
Confined Water ◽  
Swelling Properties ◽  
Compacted Bentonite ◽  
Buffer Material ◽  
Swelling Factor

Compacted bentonite is the main candidate for buffer material in several plans for spent nuclear fuel repositories. One of its important properties is high swelling capacity, which is caused by interaction between water molecules and exchangeable cations. This interaction makes bentonite behave differently from capillary materials. In this article, a model for thermo-hydro-mechanical state of partially water saturated bentonite is presented. It couples the water retention and swelling properties with introduction of the swelling factor in effective strain. The Helmholz energy density determines the state with a relatively small set of independent parameters: swelling pressure, swelling factor, maximum confined water content and the reference state. The model parameters are determined from experimental data for FEBEX bentonite, and as a simple consistency check, confined suction curves are calculated and compared to test results. Consistency of the model with observations on nano- and microscale of bentonite is also discussed.

Ultrasonic Velocities Measurement in Compacted Bentonite-Sand Mixtures for Saturation Level Evaluation

2018 ◽  
Author(s):  
Shun Kimura ◽  
Hideharu Takahashi ◽  
Ari Hamdani ◽  
Masanori Aritomi ◽  
Susumu Ozaki ◽  
...  
Keyword(s):  
Water Content ◽  
Water Saturation ◽  
Radioactive Waste Disposal ◽  
Saturation Level ◽  
Degree Of Saturation ◽  
Ultrasonic Velocities ◽  
Compacted Bentonite ◽  
Bentonite Buffer ◽  
Buffer Material

Compacted bentonite materials are often considered as a buffer material in the geological radioactive waste disposal. This bentonite is expected to fill up the space between the waste and the surrounding ground by swelling. Therefore, understanding the surrounding ground, i.e., groundwater behavior in bentonite, as a buffer material, is essential in order to evaluate the bentonite buffer performance and guarantee long-term safety. The monitoring system of the water saturation level in compacted bentonite is required because water content in buffer material may influence its elastic properties. In this study, the correlation between water content and elasticity in unsaturated compressed bentonite was experimentally evaluated. The evaluation was done by measuring the sound velocity of both longitudinal wave and transverse wave. As a result, it can be confirmed that ultrasonic velocities could evaluate a degree of saturation and bulk modulus of compacted bentonite.

Model for the Microbiological Corrosion of Copper Containers in a Deep Geologic Repository

2003 ◽  
Vol 807 ◽  
Author(s):  
Fraser King ◽  
Miroslav Kolar ◽  
Simcha Stroes-Gascoyne ◽  
Peter Maak
Keyword(s):  
Microbial Activity ◽  
Corrosion Behaviour ◽  
Geologic Repository ◽  
Microbiological Corrosion ◽  
Microbiological Processes ◽  
Bentonite Buffer ◽  
Buffer Material ◽  
The Impact ◽  
Aerobic And Anaerobic

ABSTRACTA model has been developed to predict the impact of microbiological processes on the long-term corrosion behaviour of copper containers in a deep geologic repository. The model accounts for a range of aerobic and anaerobic microbial processes. Various factors expected to limit the extent of microbial activity in the repository, such as the lack of water, evolving redox conditions, and the nutrient-poor environment, are taken into account in the model. Amongst other effects, the model predicts that microbial activity will not occur close to the container in the presence of highly compacted bentonite buffer material.

Laboratory gas injection tests of compacted bentonite buffer material for TRU waste disposal

2014 ◽  
Vol 400 (1) ◽  
pp. 521-529 ◽  
Author(s):  
Kazuto Namiki ◽  
Hidekazu Asano ◽  
Shinichi Takahashi ◽  
Tomoyuki Shimura ◽  
Ken Hirota
Keyword(s):  
Waste Disposal ◽  
Gas Injection ◽  
Compacted Bentonite ◽  
Bentonite Buffer ◽  
Buffer Material

scholarly journals Study Of Factors Affecting The Thermal Conductivity Of Iraqi Bentonite

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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