Systematic experimental research on melt-jet fragmentation behavior under severe accident in sodium-cooled fast reactor using molten stainless steel

This study aims to provide a thorough analysis of corium-fragmentation characteristics under sodium-cooled fast reactor (SFR) severe accidents, with a special emphasis on quantitatively evaluating the properties of generated fuel fragments. A visualized thermo-hydraulic characteristics in a melt coolant interaction-II apparatus is designed and built, and an array of simulative tests are conducted by discharging a fused stainless-steel jet into the coolant. Quantitative data, including the agglomerate mass fraction, fragment-size distribution, fragment mean diameter, particle-bed porosity, and granule sphericity, are obtained, and the influences of melt temperature, water temperature, melt-penetration speed, melt mass, and water depth on the fragmentation behavior of the fused stainless-steel jet are systematically analyzed in detail. Moreover, we compare the experimental data with theoretical results. These experimental results provide data to support the development and verification of SFR severe-accident analysis codes in China. © The Author(s), under exclusive licence to China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society 2026.