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A microcell UO2 pellet, as an accident-tolerant fuel pellet, is being developed to enhance the accident tolerance of nuclear fuels under accident conditions as well as the fuel performance under normal operation conditions.Improved capture-ability for highly radioactive and corrosive fission product (Cs and I) is the distinct feature of a ceramic microcell UO2 pellet, and the enhanced pellet thermal conductivity is that of a metallic microcell UO2 pellet. The fuel temperature can be effectively decreased by enhanced thermal conductivity.In this study, the material concepts of metallic and ceramic microcell UO2 pellets were designed, and the fabrication process of microcell UO2 pellets embodying the designed concept was developed. We successfully implemented the microcell UO2 pellets and produced microcell UO2 pellets.In addition, an assessment of the out-of-pile properties of a microcell UO2 pellet was performed, and the in-reactor performance and behavior of the developed microcell pellets were evaluated through a Halden irradiation test. According to the expectations, the excellent performance of the microcell UO2 pellets was confirmed by the online measurement data of the Halden irradiation test. Keywords: Accident-Tolerant Fuel, Fission Product Retention, Halden Irradiation Test, Microcell UO2 Pellet, Thermal Conductivity
Kim et al. (Thu,) studied this question.