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EXAFS analysis of uranium(IV) and thorium(IV) complexes in concentrated CaCl$$_{2}$$ solutions

Uehara, Akihiro*; Fujii, Toshiyuki*; Matsuura, Haruaki*; Sato, Nobuaki*; Nagai, Takayuki  ; Minato, Kazuo ; Yamana, Hajimu*; Okamoto, Yoshihiro  

The coordination of U$$^{4+}$$ and Th$$^{4+}$$ in CaCl$$_{2}$$ hydrate melts was studied by U and Th $$L$$$$_{rm III}$$ edge extended X-ray absorption fine structure (EXAFS) spectroscopy. It was confirmed that, with the decrease of concentration from 6.9 M CaCl$$_{2}$$ to 4 M CaCl$$_{2}$$, the Cl$$^{-}$$ ion coordination number $$N$$$$_{rm Cl}$$ in the U$$^{4+}$$ coordination sphere decreased from 3.4 to 1.3, while the hydration number $$N$$$$_{rm O}$$ in it increased from 4.5 to 6.7. The combined coordination number $$N$$$$_{rm O}$$ + $$N$$$$_{rm Cl}$$ of U$$^{4+}$$ in concentrated Cl$$^{-}$$ solution (8.0) was lower than that in 1.5 M perchloric acid aqueous solution (9.0). For Th$$^{4+}$$, with the decrease of concentration from 6.9 to 4 M CaCl$$_{2}$$, $$N$$$$_{rm Cl}$$ in the Th$$^{4+}$$ coordination sphere decreased from 1.9 to 1.5, while $$N$$$$_{rm O}$$ in it increased from 7.6 to 8.8. The $$N$$$$_{rm O}$$ + $$N$$$$_{rm Cl}$$ of Th$$^{4+}$$ in concentrated Cl$$^{-}$$ solution was 9.0 which was similar to that in 1.5 M perchloric acid. It was found that the bond distance of U-Cl was shorter than that of Th-Cl because of low $$N$$$$_{rm O}$$ to U$$^{4+}$$.

Language

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English

Journal

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Proceedings in Radiochemistry

Volume

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1

Number

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1

Pages

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p.161 - 165

Publication Year/Month

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2011/09

Meeting title

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4th International Conference of Asia-Pacific Symposium on Radiochemistry (APSORC '09)

Held date

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2009/11

Location (city)

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Napa

Location (country)

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U.S.A.

Patent information

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PDF

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Paper URL

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http://www.oldenbourg-link.com/doi/abs/10.1524/rcpr.2011.0030

DOI for research data

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Keywords

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no keyword

Research Facility

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Press Release

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Article of JAEA R&D Review

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Cooperating Institute

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Accesses

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- Accesses

InCites™

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Altmetrics

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