Morphologic and chemical characterization of products from hydrolysis of UF6

Abstract

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.

Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

“…Uranyl fluoride (UO 2 F 2 ), produced by the hydrolysis of UF 6 , is another intermediate in the deconversion of UF 6 to UO 2 . Solid UO 2 F 2 will precipitate out whenever UF 6 is allowed to come into contact with moisture [6][7][8]-for example, when UF 6 gas lines are not sufficiently dry or if a storage cylinder has been structurally compromised.…”

Morphology of U3O8 materials following storage under controlled conditions of temperature and relative humidity

“…It is not possible to determine if either the schoepite phases are redistributing between different schoepite phases without changing the ratio of UO 3 :H 2 O due to dissolution and precipitation during storage over this time, or progressing from one schoepite phase to another. Material stored under the lower temperature conditions (1 or 3) appears to be clumped/massive conglomerates of sub-rounded and irregular clumps that included fines and scale decorations [1,2]. Image of S1, L1, and L2 reveal that changes in the morphology were particularly notable following storage under higher relative humidity and temperature (Condition 4).…”

“…Material storage under controlled temperature and relative humidity Aging vessels fabricated from Swagelok fittings are described elsewhere [1,2,21]. The four storage conditions of temperature and relative humidity used in these experiments were: Condition 1 (5°C and 25 %), Condition 2 (37°C and 15 %), Condition 3 (5°C and 97 %), and Condition 4 (37°C and 89 %).…”

“…Temporal changes in the morphology of uranium oxide materials could provide insight into process and/or storage history [1][2][3][4][5]. Process variables inherent in the synthesis of nuclear materials are known to influence the morphology of uranium oxide products [4,[6][7][8][9][10][11][12][13][14][15].…”

Uranium aerosols at a nuclear fuel fabrication plant: Characterization using scanning electron microscopy and energy dispersive X-ray spectroscopy

“…The spherical shape and size strongly indicates UO 2 F 2 . Several studies have shown that formation of UO 2 F 2 from UF 6 in a humid environment results in spherical shapes of about ≅0.2-2.0 μm diameter [33][34][35]. The presence of nitrogen is slightly surprising, but could be explained by attachment of nitrogen-rich materials present in the atmosphere.…”