Two-Dimensional Thermal-Hydraulic Calculations for the Mol 7C Experiments with the Computer Code BACCHUS

The computer code BACCHUS has been developed for thermal-hydraulic calculations of coolant flows in reactor geometries with hexagonal pin arrangements. It has been used in its two-dimensional single-phase version for the interpretation of the first three experiments of the in-pile series Mol 7C in a sodium-cooled 37-pin bundle. The modeling of experimental details is described. Results for the coolant flow and temperature distributions in the blocked region are presented for selected Mol 7C cases for steady-state and transient conditions up to boiling inception. The extrapolation of the results to reactor conditions is done in several steps. First, the features that are specific for the Mol 7C experiments are removed, and then the bundle is enlarged to a size typical for reactors.