Effect of bed configuration on pebble flow uniformity and stagnation in the pebble bed reactor

•Pebble flow uniformity and stagnation characteristics are very important for HTR-PM.•Arc- and brachistochrone-shaped configuration effects are studied by DEM simulation.•Best bed configurations with uniform flow and no stagnated pebbles are suggested.•Detailed quantified characteristics of bed configuration effects are shown for explanation.

Pebble flow uniformity and stagnation characteristics are very important for the design of pebble bed high temperature gas-cooled reactor. Pebble flows inside some specifically designed contraction configurations of pebble bed are studied by discrete element method. The results show the characteristics of stagnation rates, recycling rates, radial distribution of pebble velocity and residence time. It is demonstrated clearly that the bed with a brachistochrone-shaped configuration achieves optimum levels of flow uniformity and recycling rate concentration, and almost no pebbles are stagnated in the bed. Moreover, the optimum choice among the arc-shaped bed configurations is demonstrated too. Detailed information shows the quantified characteristics of bed configuration effects on flow uniformity. In addition, a good design of the pebble bed configuration is suggested.