Determination of intermediates and products of the uranyl aerosol formation in UF6 hydrolysis in the gas phase

Christian Mark Salvador; Jason M. Richards; Shannon M. Mahurin; Meng Dawn Cheng; Joshua A. Hubbard

doi:10.1039/d3re00665d

Determination of intermediates and products of the uranyl aerosol formation in UF₆ hydrolysis in the gas phase

Christian Mark Salvador, Jason M. Richards, Shannon M. Mahurin, Meng Dawn Cheng, Joshua A. Hubbard

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

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Abstract

The reaction pathway of hydrolysis of UF₆ to form UO₂F₂ particles is an essential insight in nuclear fuel processing; however, it is still limited to theoretical calculations. Herein, we present the identification of the intermediates and products using various gas precursor concentrations and molecular beam mass spectrometer (MBMS). Compounds containing different uranium atom counts were identified by exposing 300 and 2323 ppm water to 200 ppm UF₆. Non-uranium compounds (e.g., (HF)₃(H₂O)H, (HF)₄H, and (H₂O)₂(HF)₃) dominate the mass spectra in terms of absolute signal intensity. These compounds were dependent on the initial concentration of UF₆ based on the linear relationship observed between products and gas reactant. Uranium compounds were characterized by UF₆, UO₃, and UO₂F₂ core molecules, with each species existing predominantly in a certain water concentration. Monomeric compounds (e.g., UF₆(HF)₂(H₂O)₇, UO₂F₂(HF)₇H, and UO₂F₂(HF)₅(H₂O)₃) or species with one uranium atom had high fluorine to uranium ratio (F/U) due to several HF units bonded with the uranium core. Dimeric (e.g. (UO₂F₂)₂(H₂O) and (UF₆)₂(H₂O)4(HF)₃H) and trimeric (e.g., (UO₃)(UO₂F₂)₂(HF)(H₂O)₃ and (UO₂F₂)₂UF₆H₂F) compounds persisted in high masses with low F/U and H/U ratios. Moreover, ramping of UF₆ concentration (50-231 ppm) at fixed water content (1.3% Rh or 300 ppm) showed different trends among 949 ions, with some following consistently with molecular identification (e.g., (UO₃)₃(HF)₂(H₂O)H). Overall, this study provided important information regarding the formation pathway of UO₂F₂, which will be essential in chemical modelling studies. The vast information generated from mass spectrometric runs merits cluster evaluation and factorization to yield more information on the U-O-F system.

Original language	English
Pages (from-to)	1776-1783
Number of pages	8
Journal	Reaction Chemistry and Engineering
Volume	9
Issue number	7
DOIs	https://doi.org/10.1039/d3re00665d
State	Published - Apr 2 2024

Funding

This research was supported by the National Nuclear Security Administration of the Department of Energy. Oak Ridge National Laboratory is managed by UT-Battelle, LLC for the U.S. Department of Energy under contract DE-AC05-00OR22725. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & 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 paper describes objective technical results and analysis. The research was funded by the National Nuclear Security Administration. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( https://energy.gov/downloads/doe-public-access-plan ).

Funders	Funder number
Oak Ridge National Laboratory
Sandia National Laboratories
U.S. Department of Energy	DE-AC05-00OR22725
U.S. Department of Energy
National Nuclear Security Administration	DE-NA0003525
National Nuclear Security Administration

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title = "Determination of intermediates and products of the uranyl aerosol formation in UF6 hydrolysis in the gas phase",

abstract = "The reaction pathway of hydrolysis of UF6 to form UO2F2 particles is an essential insight in nuclear fuel processing; however, it is still limited to theoretical calculations. Herein, we present the identification of the intermediates and products using various gas precursor concentrations and molecular beam mass spectrometer (MBMS). Compounds containing different uranium atom counts were identified by exposing 300 and 2323 ppm water to 200 ppm UF6. Non-uranium compounds (e.g., (HF)3(H2O)H, (HF)4H, and (H2O)2(HF)3) dominate the mass spectra in terms of absolute signal intensity. These compounds were dependent on the initial concentration of UF6 based on the linear relationship observed between products and gas reactant. Uranium compounds were characterized by UF6, UO3, and UO2F2 core molecules, with each species existing predominantly in a certain water concentration. Monomeric compounds (e.g., UF6(HF)2(H2O)7, UO2F2(HF)7H, and UO2F2(HF)5(H2O)3) or species with one uranium atom had high fluorine to uranium ratio (F/U) due to several HF units bonded with the uranium core. Dimeric (e.g. (UO2F2)2(H2O) and (UF6)2(H2O)4(HF)3H) and trimeric (e.g., (UO3)(UO2F2)2(HF)(H2O)3 and (UO2F2)2UF6H2F) compounds persisted in high masses with low F/U and H/U ratios. Moreover, ramping of UF6 concentration (50-231 ppm) at fixed water content (1.3% Rh or 300 ppm) showed different trends among 949 ions, with some following consistently with molecular identification (e.g., (UO3)3(HF)2(H2O)H). Overall, this study provided important information regarding the formation pathway of UO2F2, which will be essential in chemical modelling studies. The vast information generated from mass spectrometric runs merits cluster evaluation and factorization to yield more information on the U-O-F system.",

author = "Salvador, {Christian Mark} and Richards, {Jason M.} and Mahurin, {Shannon M.} and Cheng, {Meng Dawn} and Hubbard, {Joshua A.}",

note = "Publisher Copyright: {\textcopyright} 2024 The Royal Society of Chemistry.",

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doi = "10.1039/d3re00665d",

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AU - Salvador, Christian Mark

AU - Richards, Jason M.

AU - Mahurin, Shannon M.

AU - Cheng, Meng Dawn

AU - Hubbard, Joshua A.

PY - 2024/4/2

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N2 - The reaction pathway of hydrolysis of UF6 to form UO2F2 particles is an essential insight in nuclear fuel processing; however, it is still limited to theoretical calculations. Herein, we present the identification of the intermediates and products using various gas precursor concentrations and molecular beam mass spectrometer (MBMS). Compounds containing different uranium atom counts were identified by exposing 300 and 2323 ppm water to 200 ppm UF6. Non-uranium compounds (e.g., (HF)3(H2O)H, (HF)4H, and (H2O)2(HF)3) dominate the mass spectra in terms of absolute signal intensity. These compounds were dependent on the initial concentration of UF6 based on the linear relationship observed between products and gas reactant. Uranium compounds were characterized by UF6, UO3, and UO2F2 core molecules, with each species existing predominantly in a certain water concentration. Monomeric compounds (e.g., UF6(HF)2(H2O)7, UO2F2(HF)7H, and UO2F2(HF)5(H2O)3) or species with one uranium atom had high fluorine to uranium ratio (F/U) due to several HF units bonded with the uranium core. Dimeric (e.g. (UO2F2)2(H2O) and (UF6)2(H2O)4(HF)3H) and trimeric (e.g., (UO3)(UO2F2)2(HF)(H2O)3 and (UO2F2)2UF6H2F) compounds persisted in high masses with low F/U and H/U ratios. Moreover, ramping of UF6 concentration (50-231 ppm) at fixed water content (1.3% Rh or 300 ppm) showed different trends among 949 ions, with some following consistently with molecular identification (e.g., (UO3)3(HF)2(H2O)H). Overall, this study provided important information regarding the formation pathway of UO2F2, which will be essential in chemical modelling studies. The vast information generated from mass spectrometric runs merits cluster evaluation and factorization to yield more information on the U-O-F system.

AB - The reaction pathway of hydrolysis of UF6 to form UO2F2 particles is an essential insight in nuclear fuel processing; however, it is still limited to theoretical calculations. Herein, we present the identification of the intermediates and products using various gas precursor concentrations and molecular beam mass spectrometer (MBMS). Compounds containing different uranium atom counts were identified by exposing 300 and 2323 ppm water to 200 ppm UF6. Non-uranium compounds (e.g., (HF)3(H2O)H, (HF)4H, and (H2O)2(HF)3) dominate the mass spectra in terms of absolute signal intensity. These compounds were dependent on the initial concentration of UF6 based on the linear relationship observed between products and gas reactant. Uranium compounds were characterized by UF6, UO3, and UO2F2 core molecules, with each species existing predominantly in a certain water concentration. Monomeric compounds (e.g., UF6(HF)2(H2O)7, UO2F2(HF)7H, and UO2F2(HF)5(H2O)3) or species with one uranium atom had high fluorine to uranium ratio (F/U) due to several HF units bonded with the uranium core. Dimeric (e.g. (UO2F2)2(H2O) and (UF6)2(H2O)4(HF)3H) and trimeric (e.g., (UO3)(UO2F2)2(HF)(H2O)3 and (UO2F2)2UF6H2F) compounds persisted in high masses with low F/U and H/U ratios. Moreover, ramping of UF6 concentration (50-231 ppm) at fixed water content (1.3% Rh or 300 ppm) showed different trends among 949 ions, with some following consistently with molecular identification (e.g., (UO3)3(HF)2(H2O)H). Overall, this study provided important information regarding the formation pathway of UO2F2, which will be essential in chemical modelling studies. The vast information generated from mass spectrometric runs merits cluster evaluation and factorization to yield more information on the U-O-F system.

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Determination of intermediates and products of the uranyl aerosol formation in UF₆ hydrolysis in the gas phase

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