UO2 MICROSPHERE PREPARATION for a HTGR NUCLEAR FUEL In KOREA

The weak points of fossil fuel utilization include its limited supply, air pollution, and carbon dioxide emissions. Carbon dioxide emissions, are thought to be responsible for global warming, and are now international issues. This paper describes aspects of an R&D project of an HTGR nuclear fuel particle preparation in Korea. In this study, to obtain a spherical UO₂ kernel which is the core material of the TRISO coated particle, the most important factors for the spherical UO₂ kernel preparation were the changes of the composition ratio, the viscosity of the broth solution, the frequency/amplitude of the vibrator in the wet process part, and the heating modes and gases atmosphere in the dry process part. The uranium concentration and the viscosity are 0.5~0.8 mol/L and 50~80 centi-Poise of the broth solution respectively, and the vibration frequency of the dropping system is about 100~120Hz for the most thoroughly prepared condition. Also the heating rate in the calcination process of the dried-ADU gel particles must be kept below 3^oC/min. in an air atmosphere, and the optimum conditions for the sintering process of reduced UO₃ were in a H₂ gas atmosphere and a 3 steps heating mode up to 1650 ^oC.