Diffusion and adsorption of uranyl ion in clays; Molecular dynamics study

Arima, Tatsumi*; Idemitsu, Kazuya*; Inagaki, Yaohiro*; Kawamura, Katsuyuki*; Tachi, Yukio ; Yotsuji, Kenji

Diffusion and adsorption behavior of uranyl (UO $_2^{2+}$ ) species is important for the performance assessment of radioactive waste disposal. The diffusion behaviors of UO $_2^{2+}$ , K $^{+}$ , CO $_3^{2-}$ and Cl $^{-}$ and H $_{2}$ O in the aqueous solutions were evaluated by molecular dynamics (MD) calculations. The diffusion coefficient (De) of UO $_2^{2+}$ is the smallest and is 26% less than the self-diffusion coefficient of H $_{2}$ O. For the aqueous solution with high concentration of carbonate ions, uranyl carbonate complexes: UO $_{2}$ CO $_{3}$ and UO $_{2}$ (CO $_{3}$ ) $^{2-}$ can be observed. For the clay (montmorillonite or illite)-aqueous solution systems, the adsorption and diffusion behaviors of UO $_2^{2+}$ and K $^{+}$ were evaluated by MD calculations. The distribution coefficients (Kd) increase with the layer charge of clay, and Kd of UO $_2^{2+}$ might be smaller than that of K $^{+}$ . Further, their two-dimensional diffusion coefficients were relatively small in the adsorption layer and were extremely small for illite with higher layer charge.

Language	:	English
Journal	:	Progress in Nuclear Energy
Volume	:	92
Number	:
Pages	:	p.286 - 297
Publication Year/Month	:	2016/09
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Paper URL	:	https://doi.org/10.1016/j.pnucene.2016.03.006
DOI for research data	:
Keywords	:	Molecular dynamics simulation; uranyl; carbonate; complex; montmorillonite; illite; diffusion; adsorption; layer charge
Research Facility	:	ENTRY(地層処分基盤研究施設)
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Article of JAEA R&D Review	:
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Registration No. : AA20140362
JAEA Abstracts No. : 44001418
Paper Submission No. : 18085

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