TY - JOUR
T1 - Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO3, U2O7, and UO4
AU - Guo, Xiaofeng
AU - Wu, Di
AU - Xu, Hongwu
AU - Burns, Peter C.
AU - Navrotsky, Alexandra
N1 - Funding Information:
Calorimetric studies at UC Davis and data analysis were supported by the Materials Science of Actinides, an Energy Frontier Research Center funded by the U.S. Department of Energy , Office of Science , Office of Basic Energy Sciences under Award DESC0001089 . X. G was supported by a Seaborg postdoctoral fellowship from the Laboratory Directed Research and Development (LDRD) program, through the G. T. Seaborg Institute, of Los Alamos National Laboratory (LANL), which is operated by Los Alamos National Security LLC, under DOE Contract DE-AC52-06NA25396 . We thank Sabrina Labs and Dirk Bosbach for providing the initial studtite sample. Appendix A
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2016/9/1
Y1 - 2016/9/1
N2 - 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.
AB - 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.
KW - Calorimetry
KW - Enthalpy of formation
KW - Nuclear fuel alteration
KW - Studtite
KW - UO
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U2 - 10.1016/j.jnucmat.2016.06.014
DO - 10.1016/j.jnucmat.2016.06.014
M3 - Article
AN - SCOPUS:84975514362
SN - 0022-3115
VL - 478
SP - 158
EP - 163
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
ER -