Theoretical and experimental research progress on pebble flow and effective thermal conductivity in pebble-type HTGR

Pebble flow and effective thermal conductivity are essential for design, operating, and safety analysis of pebble-type HTGR. The Institute of Nuclear and New Energy Technology at Tsinghua University has recently conducted experimental, theoretical and simulation studies on the pebble flow and effective thermal conductivity. The mechanisms of pebble flow, pebble spindle and radial diffusion, geometrical optimization of pebble bed, effects of physical parameters, pebble flow regime characterization, and modeling methods of thermal radiation in pebble beds have been well explored. After a comprehensive review, the next research program was pointed out in the paper. (authors)