Fragmentation of fuel particles in rolling U3Si2-Al dispersion fuel plates

Abstract

The Nuclear and Energy Research Institute (IPEN-CNEN/SP) has recently developed a process to produce the nuclear fuel required to run the Brazilian Multipurpose Reactor (RMB), using U3Si2-Al dispersion in plate-type fuel elements. Since the late 1980s, regular production of dispersion-based fuel plates has kept the maximum fines content (<44 μm) of 20 wt%. However, IPEN’s U3Si2 powder manufacturing process typically generates fines between 25 and 30 wt%, making it necessary to discard and recycle about 5 to 10 wt% of the powder during manufacturing. The severe fines requirements necessitate careful comminution with multiple intermediate screening steps, which has a negative impact on RMB’s fuel production scalability (60 elements per year). To improve the current fines content specification for the powder, this study focuses on looking into U3Si2 particle fragmentation during fuel plate manufacturing. Quantitative microscopy methods and image analysis were employed. The findings revealed a significant increase in fines content during the rolling process, with levels reaching up to 59 wt%. Hence, to ensure high-quality dispersion, it becomes crucial to specify the fines content in the fuel plate obtained after rolling rather than just in the original powder. The results recommend that a new U3Si2 powder specification could allow a maximum fine content of 30 wt%. More research is ongoing to confirm this recommendation.