In the frame of the SARNET-2 project the models implemented into the fuel-coolant interaction codes were analysed and compared. A summary of knowledge gained regarding understanding and improvements of modelling was provided, as well as priorities for further research activities.
COBISS.SI-ID: 27889447
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
Melt droplet solidification is one major phenomenon acting on the mitigation of the strength of vapour explosions in situations related to nuclear safety. The modelling of solidification effects is then an important challenge for the evaluation of fuel–coolant interaction. An attempt for modelling the crust that might develop around melt droplets and its effect on the fine fragmentation within an Eulerian formulation of the flow equations, with application to the MC3D code, is presented. A physically-based modelling of the melt droplets temperature profile and a fragmentation criterion for partly solidified droplets is used in the proposed approach. Also the potential effect of solidification on the vapour explosion strength is shown.
COBISS.SI-ID: 28297767
The modelling capabilities of fuel-coolant interaction codes to study the vapour explosion phenomenon in light-water reactors were already proven in the frame of the OECD SERENA and EU SARNET programmes. On the other hand, the applicability of the codes for the fuel-sodium interaction must still be assessed because thermo-dynamical properties of sodium are very different from those of water. In the paper, the applicability of the MC3D code (IRSN, France) was examined. The main objectives were to improve the heat transfer modelling and to simulate the mixing of the melt with sodium. For that purpose, the FARO-TERMOS (JRC Ispra, Italy) experiments were analysed and simulated. The analyses of experimental results highlighted the importance of the melt solidification and the sodium vapour pressure curve on the strength of the vapour explosion. The sensitivity study highlighted the effect of the melt droplet quenching and jet inflow modelling on the simulation results.
COBISS.SI-ID: 28547623
One of the important safety issues during a severe accident in innovative sodium cooled fast reactors is the likelihood and the consequences of a vapour explosion. In the paper a comparative analysis of the melt-sodium and melt-water mixing is used to analyse the vapour explosion potential for sodium. Additionally, the sensitivity study on the mixing of the melt with sodium is presented and discussed. The relevance of the jet inflow conditions, the melt initial temperature, and the coolant sub-cooling on the premixing conditions are highlighted. The results indicate that the potential of vapour explosion is lower in sodium than in water.
COBISS.SI-ID: 29175079