摘要
Abstract
To reduce the dust dispersion,improve the flowability of uranium plutonium mixed oxide fuel(MOX fuel)powders,and decrease the production scrap rate,the Al2O3 powders were used to simulate the MOX fuel powders,and the dry-granulation integrated technology of MOX fuel powders was systematically studied.The influence of rolling pressure,granulation time,rolling gap,and spheroidization time on the bulk packing density and granulation rate of the MOX fuel powders was investigated by metallographic microscopy,scanning electron microscopy,and screening analysis methods.The results show that with the rolling pressure increasing from 2 kN·cm-1 to 18 kN·cm-1,the bulk packing density gradually increases from 0.752±0.002 g·cm-3 to 0.813±0.002 g·cm-3,and the granulation rate(mass fraction)shows a trend of increasing first and then decreasing,with a peak of(87.50±0.30)％.The number of crack defects inside the particles increases significantly when the pressure exceeds 10 kN·cm-1.When the granulation time increases from 1 to 6,the bulk packing density continues to rise,but the granulation rate shows the characteristics of rising first and stabilizing.After 4 times of granulations,the powder proportion(mass fraction)above 150 mesh reaches(84.10±0.15)％,but after 6 times of granulations,it only rises to(84.50±0.12)％,indicating that the granulation process tends to be stable after 4 times of granulation.The increase of rolling gap causes the bulk packing density to rise first and then fall,with a peak value of 0.738±0.002 g·cm-3,meanwhile,the granulation rate continues to decline.As the spheroidization time extends,the bulk packing density gradually increases and tends to be stable,the particle shape also changes from irregular to spherical.To sum up,the spherical particles with high bulk packing density(0.815±0.004 g·cm-3)can be stably obtained when the dry granulation process parameters are comprehensively regulated as:the rolling pressure should be inferior to 10 kN·cm-1 to suppress the particle cracks,the effective granulation saturates at 4 times,the rolling gap is best to be within 1.0～2.0 mm,and the optimal spheroidization time is 2.0 h,which can effectively improve the compression and filling performance of MOX fuel powders,and provide a key technical support for the engineering application of MOX fuels.关键词
干法制粒/MOX燃料粉末/松装密度/制粒率Key words
dry granulation/MOX fuel powders/bulk packing density/granulation rate分类
矿业与冶金
