Rehydration of metastudtite in the alteration kinetics of α– and β–U3O8 in dilute aqueous solutions of hydrogen peroxide

Carmen E. Chamberlain; Tyler L. Spano; Rodney Hunt; Peter C. Burns; Andrew Miskowiec

doi:10.1016/j.jnucmat.2025.155941

Rehydration of metastudtite in the alteration kinetics of α– and β–U₃O₈ in dilute aqueous solutions of hydrogen peroxide

Carmen E. Chamberlain, Tyler L. Spano, Rodney Hunt, Peter C. Burns, Andrew Miskowiec

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

Abstract

The formation of alteration phases on uranium ore concentrates and used nuclear fuels under oxidizing conditions is key to understanding the potential mobility of radionuclides in the environment and designing optimal storage conditions of materials. However, the time-dependent distribution of alteration phases on α– and β–U₃O₈ under oxidizing conditions has yet to be explored. Here, crystalline powders of α– and β–U₃O₈ were submerged in aqueous solutions of hydrogen peroxide (1.6 × 10⁻¹ to 5.4 × 10⁻⁵ M) with aliquots of solution and solid removed for analysis at 1, 8, 15, 22, 29, 36, 46, 58, 71, and 83 days. Within one day there is significant alteration of U₃O₈ to the uranyl peroxide metastudtite, [(UO₂)(O₂)(H₂O)₂], that is replaced by studtite, [(UO₂)(O₂)(H₂O)₂]·2H₂O, within a week regardless of the polymorph of U₃O₈ or the initial concentration of H₂O₂ in solution, as determined by partial least squares regression (PLSR) of Raman spectra collected from the solids. A dissolution/reprecipitation mechanism is proposed for both the alteration of U₃O₈ to metastudtite and the subsequent alteration of both U₃O₈ and metastudtite to studtite. The two polymorphs of U₃O₈ exhibit similar rates and extents of alteration over time. The rehydration of metastudtite to studtite has not been previously reported and highlights the need for future work to determine the mechanism by which metastudtite is converted to studtite and what other conditions facilitate this rehydration.

Original language	English
Article number	155941
Journal	Journal of Nuclear Materials
Volume	615
DOIs	https://doi.org/10.1016/j.jnucmat.2025.155941
State	Published - Sep 2025

Funding

The authors thank Jordan Roach, Ali Moore, Dusty Summers, and J.J. Quinn for their support. This work was improved by helpful comments and revisions from Kathryn Peruski and two anonymous reviewers. This research was supported in part by an appointment to the Oak Ridge National Laboratory Graduate Research Student Internship Program, sponsored by the U.S. Department of Energy and administered by the Oak Ridge Institute for Science and Education. This work was sponsored in part by the National Nuclear Security Administration. Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05\u201300OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (https://www.energy.gov/doe-public-access-plan)

Keywords

Alteration of UO
Hydrolysis
Metastudtite
Studtite

Access to Document

10.1016/j.jnucmat.2025.155941

Cite this

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title = "Rehydration of metastudtite in the alteration kinetics of α– and β–U3O8 in dilute aqueous solutions of hydrogen peroxide",

abstract = "The formation of alteration phases on uranium ore concentrates and used nuclear fuels under oxidizing conditions is key to understanding the potential mobility of radionuclides in the environment and designing optimal storage conditions of materials. However, the time-dependent distribution of alteration phases on α– and β–U3O8 under oxidizing conditions has yet to be explored. Here, crystalline powders of α– and β–U3O8 were submerged in aqueous solutions of hydrogen peroxide (1.6 × 10−1 to 5.4 × 10−5 M) with aliquots of solution and solid removed for analysis at 1, 8, 15, 22, 29, 36, 46, 58, 71, and 83 days. Within one day there is significant alteration of U3O8 to the uranyl peroxide metastudtite, [(UO2)(O2)(H2O)2], that is replaced by studtite, [(UO2)(O2)(H2O)2]·2H2O, within a week regardless of the polymorph of U3O8 or the initial concentration of H2O2 in solution, as determined by partial least squares regression (PLSR) of Raman spectra collected from the solids. A dissolution/reprecipitation mechanism is proposed for both the alteration of U3O8 to metastudtite and the subsequent alteration of both U3O8 and metastudtite to studtite. The two polymorphs of U3O8 exhibit similar rates and extents of alteration over time. The rehydration of metastudtite to studtite has not been previously reported and highlights the need for future work to determine the mechanism by which metastudtite is converted to studtite and what other conditions facilitate this rehydration.",

keywords = "Alteration of UO, Hydrolysis, Metastudtite, Studtite",

author = "Chamberlain, \{Carmen E.\} and Spano, \{Tyler L.\} and Rodney Hunt and Burns, \{Peter C.\} and Andrew Miskowiec",

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year = "2025",

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doi = "10.1016/j.jnucmat.2025.155941",

language = "English",

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AU - Chamberlain, Carmen E.

AU - Spano, Tyler L.

AU - Hunt, Rodney

AU - Burns, Peter C.

AU - Miskowiec, Andrew

PY - 2025/9

Y1 - 2025/9

N2 - The formation of alteration phases on uranium ore concentrates and used nuclear fuels under oxidizing conditions is key to understanding the potential mobility of radionuclides in the environment and designing optimal storage conditions of materials. However, the time-dependent distribution of alteration phases on α– and β–U3O8 under oxidizing conditions has yet to be explored. Here, crystalline powders of α– and β–U3O8 were submerged in aqueous solutions of hydrogen peroxide (1.6 × 10−1 to 5.4 × 10−5 M) with aliquots of solution and solid removed for analysis at 1, 8, 15, 22, 29, 36, 46, 58, 71, and 83 days. Within one day there is significant alteration of U3O8 to the uranyl peroxide metastudtite, [(UO2)(O2)(H2O)2], that is replaced by studtite, [(UO2)(O2)(H2O)2]·2H2O, within a week regardless of the polymorph of U3O8 or the initial concentration of H2O2 in solution, as determined by partial least squares regression (PLSR) of Raman spectra collected from the solids. A dissolution/reprecipitation mechanism is proposed for both the alteration of U3O8 to metastudtite and the subsequent alteration of both U3O8 and metastudtite to studtite. The two polymorphs of U3O8 exhibit similar rates and extents of alteration over time. The rehydration of metastudtite to studtite has not been previously reported and highlights the need for future work to determine the mechanism by which metastudtite is converted to studtite and what other conditions facilitate this rehydration.

AB - The formation of alteration phases on uranium ore concentrates and used nuclear fuels under oxidizing conditions is key to understanding the potential mobility of radionuclides in the environment and designing optimal storage conditions of materials. However, the time-dependent distribution of alteration phases on α– and β–U3O8 under oxidizing conditions has yet to be explored. Here, crystalline powders of α– and β–U3O8 were submerged in aqueous solutions of hydrogen peroxide (1.6 × 10−1 to 5.4 × 10−5 M) with aliquots of solution and solid removed for analysis at 1, 8, 15, 22, 29, 36, 46, 58, 71, and 83 days. Within one day there is significant alteration of U3O8 to the uranyl peroxide metastudtite, [(UO2)(O2)(H2O)2], that is replaced by studtite, [(UO2)(O2)(H2O)2]·2H2O, within a week regardless of the polymorph of U3O8 or the initial concentration of H2O2 in solution, as determined by partial least squares regression (PLSR) of Raman spectra collected from the solids. A dissolution/reprecipitation mechanism is proposed for both the alteration of U3O8 to metastudtite and the subsequent alteration of both U3O8 and metastudtite to studtite. The two polymorphs of U3O8 exhibit similar rates and extents of alteration over time. The rehydration of metastudtite to studtite has not been previously reported and highlights the need for future work to determine the mechanism by which metastudtite is converted to studtite and what other conditions facilitate this rehydration.

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KW - Hydrolysis

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