Investigation on validation of scale-up manufacture technologies of overcoating particles for HTR fuel elements

A set of overcoating equipment with a single batch output of 80–100 kg overcoated particles was developed. The experimental results obtained by using the optimized process validated that the equipment and process can not only maintain a high yield within a wide range of process parameters, but also be suitable for producing in a wide range of batch size. By studying the particle size distributions (PSDs) of different batches of overcoated particles and the transformations of PSDs and sphericity during a single batch production, combined with the movement law of particles in the overcoating drum, the reasons for the transformation of PSDs from near normal to positive skewness to negative skewness during the overcoating process was revealed. The origin of the formation of abnormal particles with different shapes was explained by analyzing the details of the defects of odd-shaped particles. The technology in this study can effectively improve the productivity, production efficiency and quality of overcoated particles, which can meet the demand of mass manufacture of fuel elements for HTR.