Japan Geoscience Union Meeting 2021

Presentation information

Print

[E] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-GE Geological & Soil Environment

[A-GE28] Energy-Environment-Water Nexus and Sustainable Development

Thu. Jun 3, 2021 1:45 PM - 3:15 PM Ch.12 (Zoom Room 12)

convener:Ming Zhang(Research Promotion Division, Geological Survey of Japan, AIST), Yonghong Hao(Tianjin Normal University), Jet-Chau Wen(National Yunlin University of Science and Technology), Ken Kawamoto(Graduate School of Science and Engineering, Saitama University), Chairperson:Ming Zhang(Research Promotion Division, Geological Survey of Japan, AIST), Ken Kawamoto(Graduate School of Science and Engineering, Saitama University), Jet-Chau Wen(National Yunlin University of Science and Technology), Yonghong Hao(Tianjin Normal University)

2:25 PM - 2:40 PM

[AGE28-04] Gas Transport and Pore Structural Parameters of Granulated Bentonite Mixtures at Varied Densities

*Mazhar Nazir1, Akihiro Matsuno1, Ken Kawamoto1, Sakaki Toshihiro2 (1.Graduate School of Science and Engineering, Saitama University, Japan, 2.Environmental Science and Engineering Consulting, Japan)

Keywords:Radioactive waste disposal, granulated bentonite mixtures (GBM), gas transport parameter, pore structural parameters, Microfocus X-ray computed tomography (MFXCT)

Granulated bentonite mixtures (GBM) are being evaluated as a candidate buffer material in the deep geological disposal of radioactive waste owing to ease of installation and good compaction characteristics. Various gases are generated in the repository by several mechanisms, and the transport of these gases through GBM occur by advection and diffusion. Understanding gas diffusion coefficient, air permeability and their dependence on pore structural parameters such as air-filled porosity, pore size distribution and pore tortuosity-connectivity is essential to characterize the diffusive and advective transport of gases through GBM. In this study, GBM prepared from OK Bentonite (Kunimine Industries, Japan) were used to measure the gas transport parameters by direct and indirect observations. First, air-dried OK bentonite grains (T = 20º C, RH = 60%) were sieved and graded to obtain a grain size distribution between 0.075 mm and 9.5 mm. The samples were then packed, in 100 cm3 acrylic cylindrical cores at varied densities ranging from 1.09 ~ 1.75 g/cm3, using a hand compaction. Gas transport parameters such as air permeability (ka) and gas diffusion coefficient (Dp) were measured in the laboratory and the pore structural parameters such as equivalent pore diameter for gas flow and diffusion-based tortuosity were estimated (indirect approach). The pore network and structure of the tested samples were also visualized and analyzed by using a Microfocus X-ray computed tomography (MFXCT) system (direct approach). Finally, correlations of the pore structural parameters evaluated from indirect and direct approaches were examined to discuss the effect of packed densities on the gas transport parameters of air-dried GBM.