Mass transport parameter models for bentonite based on the microstructural analysis

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03301
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geotechnical engineering
• Research Institution: Saitama University
• Principal Investigator: Kawamoto Ken 埼玉大学, 理工学研究科, 教授 (50292644)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: ベントナイト / 物質移動 / 微視的構造解析 / ガス拡散 / 熱伝導

Outline of Final Research Achievements

Bentonite can be expected as a filling material between the canister of radioactive waste and surrounding underground geological deposit in the engineering barrier system. In this study, two kinds of bentonite materials such as granular bentonite under different humidity and packed conditions and block bentonite were used to characterize the microstructure using a microfocus X-ray CT system and to evaluate mass transport parameters for developing predictive models. Results showed that the homogeneous process of bentonite was quantified based on the temporal change in the ratio of coarse and fine grains, and both gas diffusion coefficient and air permeability of granular bentonite were evaluated well by using the predictive models considering effective air-filled porosity. These results can be expected to incorporate with the mass transfer dynamics of filling materials and to contribute to the evaluation of long-term safety of engineering barrier system.

Free Research Field

地盤環境工学

Academic Significance and Societal Importance of the Research Achievements

放射性廃棄物地層処分におけるベントナイト充填材内部の物質動態を把握するためには、媒体中の水・熱・ガス等の各種物質の移動係数を適切に評価する必要がある。本研究を通して得られた水分吸着（吸水）課程における内部均一化の定量的評価法やガス拡散係数・通気係数予測モデルは、これらの物質動態解析に直接的に組み込まれるものであり、その工学的意義は高い。今後、熱移動や力学挙動との連成解析を行うことにより、ベントナイト充填材の長期安定性を適切に評価できることが期待される。