Acta Metallurgica Sinica (English Letters) ›› 2021, Vol. 34 ›› Issue (12): 1758-1768.DOI: 10.1007/s40195-021-01230-4

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Preliminary Investigation of Preparing High Burn-Up Structure in Nuclear Fuel by Flash Sintering Using CeO2 as a Surrogate

Tongye Li1, Jing Yang1, Chong Yu1, Yihan Liang2, Yang Li2, Xinfang Zhang2()   

  1. 1Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu 610023, China
    2School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
  • Received:2020-11-07 Revised:2021-02-07 Accepted:2021-03-03 Online:2021-12-10 Published:2021-12-10
  • Contact: Xinfang Zhang
  • About author:Xinfang Zhang xfzhang@ustb.edu.cn

Abstract:

The high burn-up structure (HBS) is characterized by the grain size of 100-300 nm and a porosity of up to 20%, which is formed at the rim of the nuclear fuel pellet due to 2-3 times higher local burn-up during the in-pile irradiation. HBS is considered a new potential structure for high-performance fuels. However, it is difficult to prepare HBS by conventional sintering methods. In this study, flash sintering was used to prepare HBS using CeO2 as a surrogate for a preliminary investigation. A new experimental configuration for rapid sintering of CeO2 pellets was provided, in which the green body can be rapidly preheated and pressure-assisted by the induction heating electrodes. An insulated quartz tube was used as the die for the flash sintered samples, allowing the current to flow through the sample and providing a stable condition for applying an external pressure of approximately 5.3-7.0 MPa during flash sintering process. Using an initial electric field of 141 V cm-1 and holding for 1-7 min at the maximum current density of ~ 98 mA mm-2, CeO2 ceramics with a grain size of 114-282 nm and a relative density of 75.4-99.7% were prepared. The densification and microstructure evolution behaviors during flash sintering in this new experimental configuration have been discussed in detail. This new experimental configuration may provide a promising approach for preparing UO2 ceramics and their HBS.

Key words: High burn-up structure, Flash sintering, CeO2 ceramic, Grain growth