Design and fabrication of Gd2Zr2O7-based waste forms for U3O8 immobilization in high capacity

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• 作者：Xiaoyan Shu ; Xirui Lu ; Long Fan ; Ruizhu Yang ; Yi Ding…
• 刊名：Journal of Materials Science
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：51
• 期：11
• 页码：5281-5289
• 全文大小：3,643 KB
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• 作者单位：Xiaoyan Shu (1)
  Xirui Lu (1) (2)
  Long Fan (1)
  Ruizhu Yang (2)
  Yi Ding (1)
  Sheqi Pan (2)
  Ping Zhou (2)
  Yanlin Wu (3)
  
  1. Key Subject Laboratory of National Defense for Radioactive Waste and Environmental Security, Southwest University of Science and Technology, Mianyang, 621010, Sichuan, People’s Republic of China
  2. China Academy of Engineering Physics, Mianyang, 621900, Sichuan, People’s Republic of China
  3. Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 9808577, Miyagi, Japan
  
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Materials Science
  Characterization and Evaluation Materials
  Polymer Sciences
  Continuum Mechanics and Mechanics of Materials
  Crystallography
  Mechanics
  
• 出版者：Springer Netherlands
• ISSN：1573-4803

文摘

For the long-term radiotoxicity of uranium in nuclear waste, U₃O₈ were immobilized into Gd₂Zr₂O₇ by ceramics solidification technology. Systematic samples (Gd_1−4x U_2x )₂(Zr_1−x U _x )₂O₇ (0 ≤ x ≤ 0.25) were designed and prepared simultaneously via lattice substitution. The immobilization effects were identified by XRD, BSE, EDS, SEM, TEM, and XPS. The results show that 38.83 wt% U₃O₈ gets dissolved in Gd₂Zr₂O₇ as a single phase (corresponding to 0 ≤ x ≤ 0.14 in (Gd_1−4x U_2x )₂(Zr_1−x U _x )₂O₇), with U6+ occupies 56 at.% of the Gd3+ positions and U4+ occupies 14 at.% of the Zr4+ sites. The XRD patterns indicate that the solid solutions transform from pyrochlore to defective fluorite structure with enhanced uranium, and this is due to the difference in ionic radii between dopant ions (U6+ and U4+) and the host ions (Gd3+ and Zr4+). Grain coarsening and densification are observed with the increased uranium. Tetravalent and hexavalent uranium in waste forms are confirmed through XPS. This research reveals the good adaptability of Gd₂Zr₂O₇ in immobilizing U₃O₈.