Tham khảo tài liệu 'nuclear power operation safety and environment part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Simulation of Ex-Vessel Steam Explosion 229 Global KH-2_02 KH-1_10 Global KH-2_02 KH-1_10 w 0 3 0 25 0 2 0 15 0 1 0 05 0 0 45 0 4 0 35 0 2 4 6 Time s 8 10 Fig. 10. Calculated maximum pressures in the cavity left and maximum pressure impulses at the cavity walls right for performed explosion phase simulations jet breakup model Global KH-2_02 KH-1_10 . The time axis denotes the explosion triggering times. Influence of melt droplets solidification In the explosion simulations it was assumed that the corium droplets in the premixture can potentially undergo fine fragmentation and so contribute to the explosion escalation if the droplets bulk temperature is higher than the corium solidus temperature. This overpredicts the ability of corium droplets to efficient participate in the explosion since in reality during premixing a crust is formed on the corium droplets much earlier than the droplets bulk temperature drops below the solidus temperature Huhtiniemi et al. 1999 Dinh 2007 . This crust inhibits the fine fragmentation process and if the crust is thick enough it completely prevents it. To find out the impact of the melt droplets solidification on the explosion results for the most explosive central melt pour case C2-60 additional explosion simulations were performed considering different corium droplet bulk temperatures below which the fine fragmentation process is suppressed. In this parametric study for the minimum fine fragmentation temperatures MFFT the corium solidus temperature 2700 K default the liquidus temperature 2800 K and the temperature 2750 K in-between were taken. The simulation results are presented in Fig. 11. It may be observed that MFFT has a significant influence on the strength of the steam explosion. As is summarized in Table 9 both the maximum pressure in the cavity and the maximum pressure impulse at the cavity walls decrease with increasing MFFT. This was expected since with a higher MFFT a smaller fraction of the corium in the premixture
