Chemical reactions of bentonite in microscopic reaction fields generated using electrokinetic technique

• Project/Area Number: 17K14906
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Nuclear engineering
• Research Institution: Central Research Institute of Electric Power Industry (2019-2020); Hokkaido University (2017-2018)
• Principal Investigator: Tanaka Shingo 一般財団法人電力中央研究所, 原子力技術研究所, 特定主任研究員 (90749037)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Project Status: Completed (Fiscal Year 2020)
• Budget Amount: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000); Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2018: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
• Keywords: 放射性廃棄物処分 / ベントナイト / 界面動電現象 / 物質移行 / 間隙水化学 / 析出 / 硫酸カルシウム / 炭酸カルシウム / 石膏（硫酸カルシウム） / 方解石（炭酸カルシウム）

Outline of Final Research Achievements

For evaluating long-term barrier performance of the bentonite in geological disposal of radioactive wastes, it is necessary to clarify chemical reactions in its confined spaces. In this study, precipitation thresholds of calcium carbonate and calcium sulfate in the bentonite were successfully found using an electrokinetic technique. Furthermore, an applicability of geochemical calculation code in confined condition was verified, and optimum parameters for the compacted state were estimated. The results obtained are expected to improve long-term evaluation models for bentonite barrier performances.

Academic Significance and Societal Importance of the Research Achievements

圧縮状態にあるベントナイト緩衝材中での化学反応は、効率的にデータ取得できる実験系の構築が困難であったため、未解明な問題の１つであった。本研究では、界面動電法をベントナイト緩衝材中の鉱物析出反応に応用することで、反応の閾（しきい）条件を実験的に見出すことに成功し、この問題の解明に資する新たな実験系を提案することができた。本研究で開発した一連の手法は、圧縮状態下にある他の多孔質媒体や化学反応にも応用可能と考えられ、新たな機能性材料の創出など、他分野への波及効果も期待される。

Research Products

• [Journal Article] Electrokinetic control of the growth of gypsum aggregates in compacted montmorillonite (2019)
  • Author(s): Tanaka Shingo
  • Journal Title: Applied Clay Science Volume: 181 Pages: 105206-105206
  • DOI: 10.1016/j.clay.2019.105206
  • Peer Reviewed
• [Journal Article] Gypsum precipitation enhanced by electrokinetic method and porewater chemistry in compacted montmorillonite (2018)
  • Author(s): Tanaka Shingo
  • Journal Title: Applied Clay Science Volume: 161 Pages: 482-493
  • DOI: 10.1016/j.clay.2018.05.011
  • NAID: 120006491532
  • Peer Reviewed / Open Access
• [Presentation] ELECTROKINETIC CONTROL OF THE GROWTH OF SECONDARY MINERALS IN COMPACTED MONTMORILLONITE (2019)
  • Author(s): Tanaka Shingo
  • Organizer: 17th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere (Migration 2019)
  • Int'l Joint Research
• [Presentation] 電場による圧縮ベントナイト中の硫酸カルシウムの析出促進と間隙水化学に関する考察 (2018)
  • Author(s): 田中真悟
  • Organizer: 日本原子力学会2018春の年会