Quantitative assessment of the effect of the humic colloids in the deep groundwater environment

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K15479
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 31010:Nuclear engineering-related
• Research Institution: Japan Atomic Energy Agency
• Principal Investigator: Kimuro Shingo 国立研究開発法人日本原子力研究開発機構, 核燃料・バックエンド研究開発部門 核燃料サイクル工学研究所 環境技術開発センター, 研究職 (10752628)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 地層処分 / フミン物質 / 安全評価

Outline of Final Research Achievements

The migration behavior and chemical form of lanthanide elements (Ce, Nd, Eu, Ho) in the deep groundwater environments were investigated by the continuous filtration (0.2 micrometer filter, 10 kDa, and 3 kDa molecular weight cutoff filters). Adopted groundwater, which was collected at Horonobe underground research laboratory, contains natural organic matters (NOM), carbonate, phosphate, and etc.
It was revealed that both NOM and carbonate ion contribute the migration and chemical form of lanthanides. This result suggests the possibility of forming ternary complex species (Ln-CO3-NOM) in the deep groundwater environment.
Additionally, obtained distribution coefficients of lanthanides to NOM colloids were adapted to the safety assessment analysis (Goldshim). By the comparison of analysis results of previous safety cases, the importance of assessment of characteristic property of NOM was confirmed.

Free Research Field

溶液化学

Academic Significance and Societal Importance of the Research Achievements

本研究では、放射性廃棄物の地層処分における評価対象核種を模擬した希土類元素について、深部地下環境でどのような化学形態や移行挙動を取るのか、また、それに及ぼす天然有機物の影響はどの程度あるのかを検討した。その結果、地下水中の炭酸イオンと有機物のどちらもが大きな影響を与えることを明らかにするとともに、有機物の特性によって、既存の安全評価解析の結果が大きく変わりうることを示した。