PRODUCTION, PRECISION FORMING, AND SINTERING OF CERAMIC-GRADE UO2

摘要

A process has been developed for the consistent production of high-quality, sinterable UO2 powder. The precision forming of the powder and sintering of the green compact to a high-density body were also studied. Ammonium diuranate was precipitated from solutions of uranyl fluoride and/or uranyl nitrate and then continuously converted to UO2 in a rotating kiln. By care¬fully maintaining control conditions throughout the process, the powder produced had the property of forming green compacts of various shapes at low forming pressures without the use of binders or lubricants. The compacts sintered to a high density (> 94% of theoretical) at moderate temperatures while maintaining clean, chip-free surfaces and edges. Close diameter tolerances, ± 0.001 to ± 0.003 Inch (depending on size and shape), were met consistently without the use of a grinding operation. This departure from the conventional procedure (use of binders, lubricants, high forming pressures, and grinding to final dimensions) was developed with the aim of lowering production costs of sintered UO2 shapes. A more efficient process was needed due to the anticipated future Increase in demand for UO2 re¬actor fuel elements, as required in the Gas Cooled Reactor Programs.