Prediction of thermal-hydraulics behaviour of wall blockages in a fuel subassembly with the code BACCHUS-3D

The computer code BACCHUS has been developed for thermal-hydraulic calculations of coolant flows in fast breeder reactor geometry. It is used in its three-dimensional single-phase version to assess important thermal-hydraulic parameters for the planned 19-pin bundle in-pile local blockage experiment Mol 7C/7. Sensitive parameters of the test are identified and the safety margin of the scheduled experiments for the preirradiation period before the start of the transient is assessed. To enable application of the experimental results to reactor conditions the effect of special features of the experiment are pointed out. (orig.)