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Title: Thermodynamics of CeSiO4: Implications for Actinide Orthosilicates

Abstract

Zircon (ZrSiO4: I41/amd) can accommodate actinides, such as thorium, uranium, and plutonium. The zircon structure has been determined for several of the end member compositions of other actinides, such as plutonium and neptunium. However, the thermodynamic properties of these actinide zircon structure-types are largely unknown due to the difficulties in synthesizing these materials and handling transuranium actinides. Thus, we have completed a thermodynamic study of cerium orthosilicate, stetindite (CeSiO4), a surrogate of PuSiO4. For the first time, the standard enthalpy of formation of CeSiO4 was obtained by high temperature oxide melt solution calorimetry to be -1971.9 ± 3.6 kJ/mol. Stetindite is energetically metastable with respect to CeO2 and SiO2 by 27.5 ± 3.1 kJ/mol. The metastability explains the rarity of the natural occurrence of stetindite and the difficulty of its synthesis. Applying the obtained enthalpy of formation of CeSiO4 from this work, along with those previously reported for USiO4 and ThSiO4, we developed an empirical energetic relation for actinide orthosilicates. Here, the predicted enthalpies of formation of AnSiO4 are then made with a discussion of future strategies to efficiently immobilize Pu or minor actinides in the zircon structure.

Authors:
 [1];  [1];  [1];  [2];  [3];  [4];  [4];  [1];  [5];  [4]; ORCiD logo [1]
  1. Washington State University, Pullman, WA (United States)
  2. Univ. Montpellier, Bagnols sur Ceze (France); Univ. Montpellier, Marcoule (France)
  3. Washington State University, Pullman, WA (United States); Sichuan University, Chengdu (China)
  4. Univ. Montpellier, Bagnols sur Ceze (France)
  5. Stanford Univ., CA (United States)
Publication Date:
Research Org.:
Washington State Univ., Pullman, WA (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1651197
Grant/Contract Number:  
NE0008582
Resource Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 59; Journal Issue: 18; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Cerium orthosilicate; thermodynamics; enthalpy of formation; ceramic waste forms; rare earth minerals; actinide geochemistry; lanthanide geochemistry; stetindite

Citation Formats

Strzelecki, Andrew, Bourgeois, Clement, Kriegsman, Kyle, Estevenon, Paul, Wei, Nian, Szenknect, Stephanie, Mesbah, Adel, Wu, Di, Ewing, Rodney C., Dacheux, Nicolas, and Guo, Xiaofeng. Thermodynamics of CeSiO4: Implications for Actinide Orthosilicates. United States: N. p., 2020. Web. https://doi.org/10.1021/acs.inorgchem.0c01476.
Strzelecki, Andrew, Bourgeois, Clement, Kriegsman, Kyle, Estevenon, Paul, Wei, Nian, Szenknect, Stephanie, Mesbah, Adel, Wu, Di, Ewing, Rodney C., Dacheux, Nicolas, & Guo, Xiaofeng. Thermodynamics of CeSiO4: Implications for Actinide Orthosilicates. United States. https://doi.org/10.1021/acs.inorgchem.0c01476
Strzelecki, Andrew, Bourgeois, Clement, Kriegsman, Kyle, Estevenon, Paul, Wei, Nian, Szenknect, Stephanie, Mesbah, Adel, Wu, Di, Ewing, Rodney C., Dacheux, Nicolas, and Guo, Xiaofeng. Tue . "Thermodynamics of CeSiO4: Implications for Actinide Orthosilicates". United States. https://doi.org/10.1021/acs.inorgchem.0c01476.
@article{osti_1651197,
title = {Thermodynamics of CeSiO4: Implications for Actinide Orthosilicates},
author = {Strzelecki, Andrew and Bourgeois, Clement and Kriegsman, Kyle and Estevenon, Paul and Wei, Nian and Szenknect, Stephanie and Mesbah, Adel and Wu, Di and Ewing, Rodney C. and Dacheux, Nicolas and Guo, Xiaofeng},
abstractNote = {Zircon (ZrSiO4: I41/amd) can accommodate actinides, such as thorium, uranium, and plutonium. The zircon structure has been determined for several of the end member compositions of other actinides, such as plutonium and neptunium. However, the thermodynamic properties of these actinide zircon structure-types are largely unknown due to the difficulties in synthesizing these materials and handling transuranium actinides. Thus, we have completed a thermodynamic study of cerium orthosilicate, stetindite (CeSiO4), a surrogate of PuSiO4. For the first time, the standard enthalpy of formation of CeSiO4 was obtained by high temperature oxide melt solution calorimetry to be -1971.9 ± 3.6 kJ/mol. Stetindite is energetically metastable with respect to CeO2 and SiO2 by 27.5 ± 3.1 kJ/mol. The metastability explains the rarity of the natural occurrence of stetindite and the difficulty of its synthesis. Applying the obtained enthalpy of formation of CeSiO4 from this work, along with those previously reported for USiO4 and ThSiO4, we developed an empirical energetic relation for actinide orthosilicates. Here, the predicted enthalpies of formation of AnSiO4 are then made with a discussion of future strategies to efficiently immobilize Pu or minor actinides in the zircon structure.},
doi = {10.1021/acs.inorgchem.0c01476},
journal = {Inorganic Chemistry},
number = 18,
volume = 59,
place = {United States},
year = {2020},
month = {9}
}

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This content will become publicly available on September 1, 2021
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