Uranium Hexafluoride Hydrolysis Reaction Dynamics from Cryogenic Layering, FTIR Spectroscopy, and Isotopic Substitution

Louis E. McNamara; Austin L. Dorris; Abigail M. Waldron; John T. Kelly; Jesse J. Lutz; K. Alicia Strange Fessler

doi:10.1021/acs.jpca.5c06078

Uranium Hexafluoride Hydrolysis Reaction Dynamics from Cryogenic Layering, FTIR Spectroscopy, and Isotopic Substitution

Louis E. McNamara
, Austin L. Dorris
, Abigail M. Waldron
, John T. Kelly
, Jesse J. Lutz
, K. Alicia Strange Fessler

Materials & Chemistry Group

Research output: Contribution to journal › Article › peer-review

Abstract

The first direct evidence that the hydrolysis reaction of uranium hexafluoride (UF₆) follows multiple competing pathways which are driven by the ratio of water to UF₆, temperature, and isotopic composition is presented. Using temperature dependent infrared spectroscopy, it is shown the hydrolysis can be prevented at temperatures below 150 K, and that water-rich environments promote the formation of uranium oxyfluoride intermediates. Spectral shifts reveal isomeric transitions and the growth of polymeric species, with reaction reversibility observed at high water concentrations. Additionally, controlled heating rates affect the emergence of intermediates. The final particulate product consistently forms as uranyl fluoride hydrate, though its morphology and spectral signature vary with reaction conditions and annealing. These findings help clarify long-standing uncertainties surrounding UF₆ hydrolysis.

Original language	English
Pages (from-to)	775-786
Number of pages	12
Journal	Journal of Physical Chemistry A
Volume	130
Issue number	4
DOIs	https://doi.org/10.1021/acs.jpca.5c06078
State	Published - Jan 29 2026

Funding

This work was produced by Battelle Savannah River Alliance, LLC under Contract No. 89303321CEM000080 with the U.S. Department of Energy. Publisher acknowledges the U.S. Government license to provide public access under the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). This work was supported by the Laboratory Directed Research and Development (LDRD) program within the Savannah River National Laboratory (SRNL). This document was prepared in conjunction with work accomplished under Contract No. 89303321CEM000080 with the U.S. Department of Energy (DOE) Office of Environmental Management (EM). Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The author(s) declare financial support was received for the research, authorship, and/or publication of this article. Financial support for this work was provided by the National Nuclear Security Administration under Defense Nuclear Nonproliferation R&D and supported by the Laboratory Directed Research and Development (LDRD) program within the Savannah River National Laboratory (SRNL).

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title = "Uranium Hexafluoride Hydrolysis Reaction Dynamics from Cryogenic Layering, FTIR Spectroscopy, and Isotopic Substitution",

abstract = "The first direct evidence that the hydrolysis reaction of uranium hexafluoride (UF6) follows multiple competing pathways which are driven by the ratio of water to UF6, temperature, and isotopic composition is presented. Using temperature dependent infrared spectroscopy, it is shown the hydrolysis can be prevented at temperatures below 150 K, and that water-rich environments promote the formation of uranium oxyfluoride intermediates. Spectral shifts reveal isomeric transitions and the growth of polymeric species, with reaction reversibility observed at high water concentrations. Additionally, controlled heating rates affect the emergence of intermediates. The final particulate product consistently forms as uranyl fluoride hydrate, though its morphology and spectral signature vary with reaction conditions and annealing. These findings help clarify long-standing uncertainties surrounding UF6 hydrolysis.",

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doi = "10.1021/acs.jpca.5c06078",

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AU - Kelly, John T.

AU - Lutz, Jesse J.

AU - Fessler, K. Alicia Strange

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AB - The first direct evidence that the hydrolysis reaction of uranium hexafluoride (UF6) follows multiple competing pathways which are driven by the ratio of water to UF6, temperature, and isotopic composition is presented. Using temperature dependent infrared spectroscopy, it is shown the hydrolysis can be prevented at temperatures below 150 K, and that water-rich environments promote the formation of uranium oxyfluoride intermediates. Spectral shifts reveal isomeric transitions and the growth of polymeric species, with reaction reversibility observed at high water concentrations. Additionally, controlled heating rates affect the emergence of intermediates. The final particulate product consistently forms as uranyl fluoride hydrate, though its morphology and spectral signature vary with reaction conditions and annealing. These findings help clarify long-standing uncertainties surrounding UF6 hydrolysis.

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Uranium Hexafluoride Hydrolysis Reaction Dynamics from Cryogenic Layering, FTIR Spectroscopy, and Isotopic Substitution

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