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Zirconolite is recognized as one of the most durable waste matrices for the disposal of high-level radioactive wastes (HLWs). In this study, HfO2 was employed as the surrogate of tetravalent actinides. Hf-bearing zirconolite-based composite waste forms (CaZr1-xHfxTi2O7) were rapidly prepared by combustion synthesis (CS) using CuO as the oxidant, where quick pressing (QP) was introduced to obtain densified samples. Similar as solid state reaction process, the Zr site of zirconolite can be totally occupied by Hf (x = 1.0) under the CS reaction. The original 2M zirconolite structure was maintained and a small amount of perovskite impurity phase was generated in the final products. The aqueous durability of representative sample (Cu-Hf-0.6) was tested, where the 42-day normalized leaching rates (LRi) of Ca, Cu, and Hf are 0.25, 3.10×10-2, and 1.11×10-8 g·m-2·d-1.


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Combustion synthesis of Hf-doped zirconolite-rich composite waste forms and the aqueous durability

Show Author's information Kuibao ZHANGa,b( )Dan YINaZongsheng HEaBaozhu LUOaHaibin ZHANGc
State Key Laboratory of Environment-friendly Energy Materials, Southwest University of Science and Technology, Mianyang 621010, China
National Defense Key Discipline Lab of Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang 621010, China
Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China

Abstract

Zirconolite is recognized as one of the most durable waste matrices for the disposal of high-level radioactive wastes (HLWs). In this study, HfO2 was employed as the surrogate of tetravalent actinides. Hf-bearing zirconolite-based composite waste forms (CaZr1-xHfxTi2O7) were rapidly prepared by combustion synthesis (CS) using CuO as the oxidant, where quick pressing (QP) was introduced to obtain densified samples. Similar as solid state reaction process, the Zr site of zirconolite can be totally occupied by Hf (x = 1.0) under the CS reaction. The original 2M zirconolite structure was maintained and a small amount of perovskite impurity phase was generated in the final products. The aqueous durability of representative sample (Cu-Hf-0.6) was tested, where the 42-day normalized leaching rates (LRi) of Ca, Cu, and Hf are 0.25, 3.10×10-2, and 1.11×10-8 g·m-2·d-1.

Keywords:

combustion synthesis (CS), nuclear waste, HfO2, zirconolite, aqueous durability
Received: 22 January 2019 Revised: 23 April 2019 Accepted: 03 May 2019 Published: 31 July 2019 Issue date: September 2019
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Publication history

Received: 22 January 2019
Revised: 23 April 2019
Accepted: 03 May 2019
Published: 31 July 2019
Issue date: September 2019

Copyright

© The author(s) 2019

Acknowledgements

We sincerely appreciate the projects supported by the National Natural Science Foundation of China (Nos. 51202203 and 51672228), the Project of State Key Laboratory of Environment-friendly Energy Materials (Nos. 16kffk05 and 17FKSY0104, Southwest University of Science and Technology), and Science Development Foundation of China Academy of Engineering Physics.

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