Consolidation of commercial-size UO 2 fuel pellets using spark plasma sintering and microstructure/microchemical analysi
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Research Letter
Consolidation of commercial-size UO2 fuel pellets using spark plasma sintering and microstructure/microchemical analysis Bowen Gong, and Tiankai Yao, Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA Cai Lu, Peng Xu, and Edward Lahoda, Westinghouse Electrical Company, Hopkins, SC 29061, USA Jie Lian, Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA Address all correspondence to Jie Lian at [email protected] (Received 22 May 2018; accepted 25 June 2018)
Abstract The development of advanced fuel fabrication technologies is important for developing accident-tolerant fuels and engineering fuels for safer and more effective nuclear energy systems. In this work, commercial-size uranium dioxide (UO2) fuel pellets with a theoretical density of 95% were consolidated by spark plasma sintering (SPS) at 1600°C for 5 min. Systematic investigations suggest uniform densification and stoichiometric UO2 with an ideal fluorite structure across the commercial-size fuel pellet, but with a distributed grain structure because of non-uniform distribution of temperature during sintering. This work demonstrates a great potential of using SPS for fabricating nuclear fuels at a cost-effective manner.
Introduction Uranium dioxide (UO2) is a widely used nuclear fuel because of its vast application in almost all types of commercial nuclear reactors, such as boiling water reactor and pressurized water reactor.[1] During severe conditions, such as Fukushima accident, zirconium metals may react with water at elevated temperature, leading to the fuel failure and the generation of hydrogen with the risk of explosion.[2] Extensive efforts are focused on the development of advanced fuels with enhanced performance and accident tolerance to improve the safety margin of the current light water reactor fleets and the development of future advanced nuclear systems. New concepts of fuels such as engineering fuels with increased grain size by sintering additive, composite fuels and high-density fuels are proposed to improve fuel behavior, performance, and safety of UO2 with the focus on fuel fabrication of UO2,[3–6] mechanical properties[3,7,8] and thermal properties.[9–12] As oxide fuels are typically fabricated by high-temperature sintering (over 1700°C) for a long duration (several tens of hours) in a reducing atmosphere,[5,6] it is highly desired to develop new fuel fabrication technologies for new concept fuel types. UO2 can also be sintered using hot pressing,[3,4] where a pressure is applied to the pellet at elevated temperature and held for a certain period of time to enhance the fuel fabrication. For example, Amato et al.[4] investigated the hot-pressing sintering mechanisms and achieved over 95% theoretical density by hot pressing at 8000 psi and 1200°C for 60 min. In addition to hot pressing, spark plasma sintering (SPS) is a field-assisted sintering technology (FAST) that works by applying high DC current
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