A criterion for the determination of the critical conditions for the hydrodynamic fine fragmentation of partly solidified melt droplets was introduced. Based on the performed experimental analysis, together with the theoretical analysis, the range of the critical conditions for the fine fragmentation of partly solidified droplets was established. The performed analysis for the corium material showed that a crust thickness of greater than 20% of the droplet radius can be considered as strong enough to prevent any fine fragmentation during a typical fuel coolant interaction explosion phase.
COBISS.SI-ID: 27691559
The analyses of the effect of the sodium properties on the key processes of the vapour explosion phenomenon have indicated that it appears difficult to have a strong escalation of pressure through a vapour explosion in sodium. Therefore, it seems that the current range of the tables applied in the MC3D code is sufficient for realistic situations. It was shown that the discrepancy between the MC3D tables and other available tables is acceptable at the present status of analyses and considering other uncertainties in the fuel coolant interaction modelling. The heat transfer modelling needs an improvement in the transition boiling regime, which is the predominant regime during the mixing of the melt droplets with sodium.
COBISS.SI-ID: 27751719
As observed from quenching experiments with sub-cooled water, the transition boiling regime could be divided into two modes: contact and non-contact. With analyses of the experiments and literature review, empirical correlations for the temperature ranges of the transition boiling regime and their modes were proposed. Also an empirical correlation for the heat transfer modelling during the non-contact mode was proposed. The correlations were fitted to the experimental data.
COBISS.SI-ID: 28326695