Densification of uranium dioxide pellets by microwave sintering for nuclear applications - CEA - Commissariat à l’énergie atomique et aux énergies alternatives
Communication Dans Un Congrès Année : 2021

Densification of uranium dioxide pellets by microwave sintering for nuclear applications

Résumé

Mixed oxides (MOX) made of PuO2 and UO2, in the form of sintered pellets, are used as fuel in nuclear reactors. The sintering step is generally carried out at high temperature (about 1700°C) in an electrical resistance furnace. Therefore, there is a need to optimize manufacturing processes and especially to reduce economic and energetic costs. In this context, microwave heating has been extensively studied as an alternative technology for sintering of ceramics. In this process, the ceramic components are directly heated by absorption of the microwaves, leading to substantial savings in processing time and energy. Up to now, few studies reported the densification of UO2 pellets by microwave sintering. The main issues of these studies are the poor reproducibility and the lack of relevant comparison between conventional and microwave sintering. Therefore, the main aim of this work is to perform a careful study of the microwave sintering of UO2 pellets. For this purpose, a suitable cavity for multimode microwave sintering was designed and fabricated. The cavity was developed to allow for heating of UO2 at high temperature under a controlled atmosphere. A sintering cell was also designed with the aim of uniformly heating the sample. The cavity and the cell were fabricated and optimized thanks to finite element simulations and preliminary tests with a surrogate of UO2. The measurement of temperature and of the sample’s shrinkage are important to control the heating cycle and to highlight possible microwave effects during sintering. For this purpose, different devices were added around the cavity for contactless measurement of the temperature (pyrometer) and of the shrinkage (optical dilatometry). Densification of the pellets was achieved in this microwave cavity with a shorter thermal cycle (lower than 4 hours) compared to conventional furnace. Different thermal treatments were tested with various temperatures and holding times. Final density and grain size of the samples were then determined. Sintered pellets with high relative densities (i.e., 91-95 % of theoretical density) and an average grain size in the range 9-11 µm were obtained.
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Dates et versions

cea-04741813 , version 1 (17-10-2024)

Identifiants

  • HAL Id : cea-04741813 , version 1

Citer

Clémence Petit, François Valdivieso, Christophe Meunier, Jérémy Croquesel, Sylvie Pillon-Eymard, et al.. Densification of uranium dioxide pellets by microwave sintering for nuclear applications. STPMF 2021, Jul 2021, Saint Etienne, France. ⟨cea-04741813⟩
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