DEM in analyses of nuclear pebble bed reactors

Abstract

Pebble bed reactors are innovative fission reactors with improved efficiency and unique safety features. These reactors differ from the conventional reactors mainly by their fuel design, which instead of rods, is based on coated fissile particles enclosed inside graphite spheres. The reactor core is a packed bed consisting of these spheres, through which the reactor coolant flows. In the research documented in this paper, DEM code LIGGGHTS is used for various analyses of pebble bed reactors: DEM is used to produce realistic reactor core geometries for subsequent reactor physical, coolant flow and heat transfer analyses. DEM analyses are also performed to investigate various reactor operation aspects, such as the flow of the spherical fuel elements through the cylindrical core geometry and insertion of a control blade into the pebble bed. DEM has been found as a very effective tool for reactor analyses.