Calculation of the PWR-1300 H3 Sequence with ASTEC V1.2 Code and Comparison with CATHARE2 V2.5 Code

The accidental H3 sequence on the French PWR-1300 reactor has been simulated using both ASTEC V1.2 and CATHARE2 V2.5 codes. The full CESAR-DIVA calculation has been performed with ASTEC until care melting and relocation in the lower plenum and vessel failure. The CATHARE2 calculation stops after core uncovery and the onset of significant fuel rod heatup. The CESAR results before DIVA start have been compared with CATHARE2 results to investigate the differences in reactor thermal-hydraulic behaviour.The ASTEC input deck has been then modified according to the CATHARE2 one, in order to batter compare the two code results. Moreover, insights from the analysis of Bethsy experiments have been taken into account in the plant modelling with ASTEC. Finally, the full CESAR-DIVA calculation has been performed using the modified ASTEC input deck and some sensitivity studies have been conducted on more uncertain key parameters.