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http://dx.doi.org/10.7474/TUS.2022.32.6.491

Feasibility Assessment on the Application of X-ray Computed Tomography on the Characterization of Bentonite under Hydration  

Melvin B., Diaz (Department of Ocean Energy & Resources Engineering, Korea Maritime and Ocean University (KMOU))
Gyung Won, Lee (Department of Ocean Energy & Resources Engineering, Korea Maritime and Ocean University (KMOU))
Seohyeon, Yun (Department of Ocean Energy & Resources Engineering, Korea Maritime and Ocean University (KMOU))
Kwang Yeom, Kim (Department of Ocean Energy & Resources Engineering, Korea Maritime and Ocean University (KMOU))
Chang-soo, Lee (Korea Atomic Energy Research Institute (KAERI))
Minseop, Kim (Korea Atomic Energy Research Institute (KAERI))
Jin-Seop, Kim (Korea Atomic Energy Research Institute (KAERI))
Publication Information
Tunnel and Underground Space / v.32, no.6, 2022 , pp. 491-501 More about this Journal
Abstract
Bentonite has been proposed as a buffer and backfill material for high-level radioactive waste repository. Under such repository environment conditions, bentonite is subjected to combined thermal, hydrological, mechanical, and chemical processes. This study evaluates the feasibility of applying X-ray CT technology on the characterization of bentonite under hydration conditions using a newly developed testing cell. The cylindrical cell is made of platic material, with a removable cap to place the sample, enabling to apply vertical pressure on the sample and to measure swelling pressure. The hydration test was carried out with a sample made of Gyeonju bentonite, with a dry density of 1.4 g/cm3, and a water content of 20%. The sample had a diameter of 27.5 mm and a height of 34 mm. During the test, water was injected at a constant pressure of 0.207 MPa, and lasted for 7 days. After one day of hydration, bentonite swelled and filled out the space inside the cell. Moreover, CT histograms showed how the hydration process induced an initial increase and later progressive decrease on the density of the sample. Detailed profiles of the mean CT value, CT standard deviation, and CT gradient provided more details on the hydration process of the sample and showed how the bottom and top regions exhibited a decrease on density while the middle region showed an increase, especially during the first two days of hydration. Later, the differences in CT values with respect to the initial state decreased, and were small at the end of testing. The formation and later reduction of cracks was also characterized through CT scanning.
Keywords
Bentonite; Hydration test; X-ray CT; High-level radioactive waste;
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Times Cited By KSCI : 3  (Citation Analysis)
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