Characterizing the degradation of [(UO2F2)(H2O)]7 4H2O under humid conditions

Under humid conditions, uranyl fluoride ([(UO2F2)(H2O)]7·4H2O) undergoes a loss of fluorine to form a uranyl hydroxide species, which can be further hydrated to form a uranyl peroxide species. X-ray diffraction data of the uranyl peroxide product is presented for the first time. In addition, the tem...

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Bibliographic Details
Published in:Journal of nuclear materials 2020-02, Vol.529, p.151889, Article 151889
Main Authors: Kirkegaard, Marie C., Ambrogio, Michael W., Miskowiec, Andrew, Shields, Ashley E., Niedziela, J.L., Spano, Tyler L., Anderson, Brian B.
Format: Article
Language:English
Subjects:
Degradation
Fluorides
Fluorine
Humidity
Organic chemistry
Peroxide
Raman spectroscopy
Reaction kinetics
Relative humidity
Spectroscopy
Uranium
Uranium oxides
Uranyl fluoride
Uranyl hydroxide
Uranyl peroxide
Vapor pressure
Water chemistry
Water vapor
X-ray diffraction
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Summary:Under humid conditions, uranyl fluoride ([(UO2F2)(H2O)]7·4H2O) undergoes a loss of fluorine to form a uranyl hydroxide species, which can be further hydrated to form a uranyl peroxide species. X-ray diffraction data of the uranyl peroxide product is presented for the first time. In addition, the temperature and humidity conditions under which these reactions occur have been clarified by a 220-day experiment using microRaman spectroscopy to track chemical changes in individual particles of uranyl fluoride. At 25 and 35∘C, uranyl fluoride is found to be stable at 32% relative humidity but not stable at and above 59% relative humidity. We show that water vapor pressure is the driving factor in formation of both the hydroxide and peroxide products. The kinetics of the transformation from uranyl fluoride into uranyl hydroxide is consistent with a denucleation reaction following the absorption of water molecules.
ISSN:0022-3115
1873-4820
DOI:10.1016/j.jnucmat.2019.151889