This title appears in the Scientific Report :
2020
Please use the identifier:
http://hdl.handle.net/2128/25872 in citations.
Please use the identifier: http://dx.doi.org/10.1016/j.jnucmat.2020.152454 in citations.
Structural changes of Nd- and Ce-doped ammonium diuranate microspheres during the conversion to U$_{1-y}Ln_y$O$_{2\pm x}$
Structural changes of Nd- and Ce-doped ammonium diuranate microspheres during the conversion to U$_{1-y}Ln_y$O$_{2\pm x}$
The structural changes of ammonium diuranate (ADU) microspheres, prepared by the sol-gel route via internal gelation, were investigated during thermal treatments in oxidative and reducing conditions. In particular, $in-situ$ simultaneous thermogravimetric analyses and $in-situ$ high-temperature scan...
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Personal Name(s): | Schreinemachers, Christian (Corresponding author) |
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Leinders, Gregory / Podor, Renaud / Lautru, Joseph / Clavier, Nicolas / Modolo, Giuseppe / Verwerft, Marc / Binnemans, Koen / Cardinaels, Thomas | |
Contributing Institute: |
Nukleare Entsorgung; IEK-6 |
Published in: | Journal of nuclear materials, 542 (2020) S. 152454 |
Imprint: |
Amsterdam [u.a.]
Elsevier Science
2020
|
DOI: |
10.1016/j.jnucmat.2020.152454 |
Document Type: |
Journal Article |
Research Program: |
GEN IV Integrated Oxide fuels recycling strategies Nuclear Waste Management |
Link: |
Published on 2020-08-17. Available in OpenAccess from 2022-08-17. Restricted Published on 2020-08-17. Available in OpenAccess from 2022-08-17. Restricted |
Publikationsportal JuSER |
Please use the identifier: http://dx.doi.org/10.1016/j.jnucmat.2020.152454 in citations.
The structural changes of ammonium diuranate (ADU) microspheres, prepared by the sol-gel route via internal gelation, were investigated during thermal treatments in oxidative and reducing conditions. In particular, $in-situ$ simultaneous thermogravimetric analyses and $in-situ$ high-temperature scanning electron microscopy investigations were carried out on un-doped ADU microspheres, and ADU microspheres doped with 10 mol% neodymium or 10 mol% cerium. Calcination in air caused the surface of the particles to crack, but with increasing temperature up to 900 °C some healing, and additionally, shrinkage occurred. The extent of the fractures and the amount of shrinkage was, however, significantly more pronounced in a particle prepared with a tetravalent Ce precursor, as compared to particles prepared with a trivalent Nd or Ce precursor. The macroscopic behaviour could be related to the release of volatile decomposition products and the calcined compositions were identified as ($Ln$-doped) α-U$_3$O$_8$ by X-ray powder diffraction. During thermal treatment in reducing conditions a transition from a ($Ln$-doped) α-U$_3$O$_8$ phase to a ($Ln$-doped) UO$_{2±x}$ phase was observed. After exposure to a hydrogen containing gas mixture, this transition occurred rapidly in un-doped particles, and in particles prepared with trivalent Nd or Ce dopant precursors at 700 °C. Despite the fast reduction reaction, severe fractures appeared in the particles above temperatures of 850 °C, indicating that such behaviour is mainly attributed to sintering effects and less to the phase transition. In contrast, a more delayed reduction reaction was observed in particles prepared with a tetravalent dopant precursor and the described effects appeared less severe. |