Characterization of the solid, airborne materials created when UF/sub 6/ reacts with moist air flowing in single-pass mode

Pickrell, P.W.

doi:10.2172/5047113

Cited by 8 publications

(11 citation statements)

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“…4 In that work, researchers found only UO 2 F 2 product for UF 6 these two values and no reaction mechanisms were proposed. Additionally, several groups have studied the particle morphology [5][6][7][8][9][10] and reactor design for the production of particles from aerosols of UF 6 . 11…”

Section: Uf 6 + H 2 O → Uof 4 + 2hfmentioning

confidence: 99%

Transition State for the Gas-Phase Reaction of Uranium Hexafluoride with Water

Garrison

Becnel

2008

J. Phys. Chem. A

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ABSTRACT. Density Functional Theory and small-core, relativistic pseudopotentials were used to look for symmetric and asymmetric transitions states of the gas-phase hydrolysis reaction of uranium hexafluoride, UF 6 , with water. At the B3LYP/6-31G(d,p)/SDD level, an asymmetric transition state leading to the formation of a uranium hydroxyl fluoride, U(OH)F 5 , and hydrogen fluoride was found with an energy barrier of +77.3 kJ/mol and an enthalpy of reaction of +63.0 kJ/mol (both including zero-point energy corrections). Addition of diffuse functions to all atoms except uranium led to only minor changes in the structure and relative energies of the reacting complex and transition state. However, a significant change in the product complex structure was found, significantly reducing the enthalpy of reaction to +31.9 kJ/mol. Similar structures and values were found for PBE0 and MP2 calculations with this larger basis set, supporting the B3LYP results. No symmetric transition state leading to the direct formation of uranium oxide tetrafluoride, UOF 4 , was found, indicating that the reaction under ambient conditions likely includes several more steps than the mechanisms commonly mentioned. The transition state presented here appears to be the first published transition state for the important gas-phase reaction of UF 6 with water.

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Section: Uf 6 + H 2 O → Uof 4 + 2hfmentioning

confidence: 99%

Transition State for the Gas-Phase Reaction of Uranium Hexafluoride with Water

Garrison

Becnel

2008

J. Phys. Chem. A

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“…The white fog is an aerosol consisting of particulate matter or particles of complicated chemical composition. After extensive characterization efforts for the particulate materials in the past few decades, we now know that the aerosol population consists of UO2F2 as a main reaction product when UF6 is in contact with H2O vapor (Kessie 1967, Bostick et al 1983, 1984, Kips et al 2007, Kips and Kristo 2009, Pickrell 1982, 1984, 1985. UF6 hydrolysis produces solid UO2F2 particles and also HF, a hazardous toxic gas, as written in Eq.…”

Section: Pathways To Airborne Uranyl Particlesmentioning

confidence: 99%

“…Previous microscopic studies of UO2F2 formation produced many micrographs (Bostick et al 1983, 1984, Kips et al 2007, Pickrell 1982, 1984, 1985. As the UO2F2 particles were produced, they were likely to be in a spherical shape at the beginning.…”

Section: Size Of Primary Particlementioning

confidence: 99%

Formation of Aerosol Nanoparticles by Gas-Phase Hydrolysis Reaction of Uranium Hexafluoride

Fugate

Richards

Hubbard

et al. 2021

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“…Pickrell investigated morphologies of hydrolyzed UF 6 following gravimetric deposition onto Formarcoated electron microscope grids made of nickel [11][12][13]. A glass or metal sample holder with UF 6 was pressurized with heat, allowing the UF 6 to be released as a liquid.…”

Section: *Manuscriptmentioning

confidence: 99%

“…As observed in Experiment 1, no differences in morphology or particle load were observed between samples collected at 1 cm versus 6 cm from the air inlet. SEM-EDS spectra indicated that the major elemental constituents were uranium, oxygen and fluorine (Supporting Information Figure S In contrast, Pickrell observed formation of ~ 10 μm agglomerates made of discrete spheroids on the order of 0.1 μm in diameter following release of liquid UF 6 to excess water, and suggested that agglomeration of particles over time was likely due to charging [11,12]. Kips reported an increase in the average particle diameter with increased relative humidity [15].…”

Section: Hydrolysis Products Deposited Onto a Carbon Conductive Tapementioning

confidence: 99%

Morphologic and chemical characterization of products from hydrolysis of UF6

Wagner

Kinkead

Paffett

et al. 2015

Journal of Fluorine Chemistry

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A c c e p t e d M a n u s c r i p t 1 HIGHLIGHTS  UF 6 hydrolysis was carried out under reaction conditions that were water deficient for preparation of UO 2 F 2 products. SEM Images of products of UF 6 hydrolysis deposited onto carbon conducting tape and aluminum tape showed different morphologies.  Morphologies of material deposited on aluminum after hydrolysis of UF 6 and stored under high humidity conditions change after one week.  Chemical characterization by powder X-ray diffraction analysis and -Fourier Transform Infrared Spectroscopy revealed formation of UOF 4 , a likely reaction intermediate in UF 6 hydrolysis.ABSTRACT: Characterization of the chemical speciation and morphologies of products formed from hydrolysis of uranium hexafluoride (UF 6 ) is important for predicting dispersion and contamination of released material, or health consequences from inhalation of air-borne particles. We report products of hydrolysis of UF 6 in which the quantity of water was insufficient for complete formation of UO 2 F 2 . Material was deposited onto carbon tape and aluminum. Scanning Electron Microscopy was employed to characterize textures and particle sizes, and powder X-ray diffraction analysis and μ-Fourier Transform Infrared Absorption spectroscopy were used to characterize chemical speciation. These results revealed that the ratio of H 2 O to UF 6, depository substrate composition, and storage conditions must be considered when evaluating chemical speciation, morphologic textures and particles size of UF 6 hydrolysis products. LA-UR-15-23846.

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Characterization of the solid, airborne materials created when UF/sub 6/ reacts with moist air flowing in single-pass mode

Cited by 8 publications

References 0 publications

Transition State for the Gas-Phase Reaction of Uranium Hexafluoride with Water

Transition State for the Gas-Phase Reaction of Uranium Hexafluoride with Water

Formation of Aerosol Nanoparticles by Gas-Phase Hydrolysis Reaction of Uranium Hexafluoride

Morphologic and chemical characterization of products from hydrolysis of UF6

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