Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO3, U2O7, and UO4
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Earth and Environmental Sciences Division
- Univ. of California, Davis, CA (United States). Peter A. Rock Thermochemistry Lab. and NEAT ORU; Washington State Univ., Pullman, WA (United States). Gene and Lina Voiland School of Chemical Engineering and Bioengineering
- Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Sciences; Univ. of Notre Dame, IN (United States). Dept. of Chemistry and Biochemistry
- Univ. of California, Davis, CA (United States). Peter A. Rock Thermochemistry Lab. and NEAT ORU
The thermal decomposition of studtite (UO2)O2(H2O)2·2H2O results in a series of intermediate X-ray amorphous materials with general composition UO3+x (x = 0, 0.5, 1). As an extension of a structural study on U2O7, this work provides detailed calorimetric data on these amorphous oxygen-rich materials since their energetics and thermal stability are unknown. These were characterized in situ by thermogravimetry, and mass spectrometry. Ex situ X-ray diffraction and infrared spectroscopy characterized their chemical bonding and local structures. This detailed characterization formed the basis for obtaining formation enthalpies by high temperature oxide melt solution calorimetry. The thermodynamic data demonstrate the metastability of the amorphous UO3+x materials, and explain their irreversible and spontaneous reactions to generate oxygen and form metaschoepite. Thus, formation of studtite in the nuclear fuel cycle, followed by heat treatment, can produce metastable amorphous UO3+x materials that pose the risk of significant O2 gas. Quantitative knowledge of the energy landscape of amorphous UO3+x was provided for stability analysis and assessment of conditions for decomposition.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC52-06NA25396; SC0001089; DESC0001089
- OSTI ID:
- 1304726
- Alternate ID(s):
- OSTI ID: 1325346
- Report Number(s):
- LA-UR-16-23089
- Journal Information:
- Journal of Nuclear Materials, Vol. 478, Issue C; ISSN 0022-3115
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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