Sorption of Cs⁺ and Eu³⁺ onto coherent and melange-type pre-neogene sedimentary rocks

ABSTRACT

Widely present in Japan’s deep subterranean formations, pre-Neogene sedimentary rocks offer an option for high-level radioactive waste (HLW) deep geological disposal due to their favorable properties. However, their barrier properties necessitate further investigation. This research examines the characteristics of pre-Neogene sedimentary rocks, focusing on two rock types: the melange type with a distinct block-in-matrix structure and the sandstone-dominant coherent type. Their ability and mechanism to sorb Cs⁺ and Eu³⁺ are assessed, and the differences between the two types are compared. The influence of inorganic carbon in groundwater and the role of clay minerals, such as illite, in the sorption of these metal ions, are highlighted. This investigation lays the groundwork for future studies on migration behaviors of radionuclides, essential for ensuring the long-term safety of HLW geological disposal.

KEYWORDS:

• Deep geological disposal
• host rock
• sorption
• cesium
• europium

Acknowledgments

The authors thank NUMO for providing the rock samples for this research. Appreciation is given to Dr. Mitsunori Honda from JAEA for the XRF analysis and Dr. Yuta Fukatsu from JAEA for the ICP-MS measurement of Europium. We also thank Kazuhiro Fukawa for XRD analysis and Masahiro Fukukawa for SEM-EDX imaging.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00223131.2024.2356767.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This research was partly supported by the “Grant-in-Aid for Scientific Research (B)” (grant no. 21H01855) of the Japan Society for the Promotion of Science.