CFD study on the supercritical carbon dioxide cooled pebble bed reactor

• An innovation concept of supercritical carbon dioxide cooled pebble bed reactor is proposed.
• Body-centered cuboid (BCCa) arrangement is adopted for the pebbles.
• S-CO2 would be a good candidate coolant for using in pebble bed reactor.

The thermal hydraulic study of using supercritical carbon dioxide (S-CO2), a superior fluid state brayton cycle medium, in pebble bed type nuclear reactor is assessed through computational fluid dynamics (CFD) methodology. Preliminary concept design of this S-CO2 cooled pebble bed reactor (PBR) is implemented by the well-known KTA heat transfer correlation and Ergun pressure drop equation. Eddy viscosity transport turbulence model is adopted and verified by KTA calculated results. Distributions of the temperature, velocity, pressure and Nusselt (Nu) number of the coolant near the surface of the middle spherical fuel element are obtained and analyzed. The conclusion of the assessment is that S-CO2 would be a good candidate coolant for using in pebble bed reactor due primarily to its good heat transfer characteristic and large mass density, which could lead to achieve lower pressure drop and higher power density.