Thermodynamic studies of studtite thermal decomposition pathways via amorphous intermediates UO3, U2O7, and UO4

JOURNAL OF NUCLEAR MATERIALS

卷:478

Article

Guo, Xiaofeng¹  Wu, Di^2,3,4  Xu, Hongwu¹  Burns, Peter C.^5,6  Navrotsky, Alexandra^2,3 

[1] Los Alamos Natl Lab, Earth & Environm Sci Div, Los Alamos, NM 87545 USA

[2] Univ Calif Davis, Peter A Rock Thermochem Lab, Davis, CA 95616 USA

[3] Univ Calif Davis, NEAT ORU, Davis, CA 95616 USA

[4] Washington State Univ, Gene & Lina Voiland Sch Chem Engn & Bioengn, Pullman, WA 99163 USA

[5] Univ Notre Dame, Dept Civil & Environm Engn & Earth Sci, Notre Dame, IN 46556 USA

[6] Univ Notre Dame, Dept Chem & Biochem, Notre Dame, IN 46556 USA

关键词: UO2;    Studtite;    Calorimetry;    Enthalpy of formation;    Nuclear fuel alteration;   

DOI  :  10.1016/j.jnucmat.2016.06.014

来源: Elsevier

【 摘 要 】

The thermal decomposition of studtite (UO2)O-2(H2O)(2)center dot 2H(2)O 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. (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

Free