Characteristics of melt-jet fragmentation behavior in coolant in nuclear reactor based on VTMCI experiments

Aimed at systematically investigating the mechanisms underlying the melt-jet fragmentation behavior in liquid metal cooled fast reactors, several series of experiments were skillfully engineered and carried out. Different molten metals were released into a water pool using the VTMCI facility. The molten metals used included the Bi-Sn-In alloy, lead-bismuth eutectic (45 wt% Pb-55 wt% Bi), lead, and lead-bismuth non-eutectic (70 wt% Pb-30 wt% Bi). This study presents a comprehensive synthesis and detailed comparative analysis of experimental data, examining the potential impact of key parameters on melt-jet fragmentation behavior. The results show that the increase in water subcooling results in an increase in particle size by up to 70%, an increase in the debris bed porosity by up to 67%, and a reduction in the debris sphericity by up to 78%. Raising the melt superheat causes particle size to decrease by as much as 33%, debris bed porosity to drop by up to 34%, and debris sphericity to rise by as much as 144%. Higher melt penetration velocity or smaller jet cross section diameter results in smaller fragment sizes by up to 34%. Increasing the water depth leads to a decrease in particle size of up to 9%, a reduction in debris bed porosity by as much as 7%, and an enhancement in debris sphericity of up to 76%. The article offers a wealth of experimental data that can enhance the validation of reactor safety analysis codes in China.

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