Investigation of metallic fuel relocation in a 19-pins bundle structure of a sodium-cooled fast reactor using Wood's metal

Since there are different fuel relocation behaviors between the metallic and oxide fuel, the metal-fueled SFRs have advantages rather than that of oxide fuel for safety issues. Gabor et al. investigated fragmentation experiments using the metallic fuel in an open sodium pool. They found highly porous debris bed which would be able to form coolable geometry. It has been also known that the molten metallic fuel would be swept out above of the core after cladding failure. Flow blockages would not also be formed due to chemical compatibility between the metallic fuel and sodium coolant. They were conducted in no coolant flow condition. As a result, eutectic mixtures between the fuel and HT-9M cladding were formed, but they were frozen in a channel. Previous studies have conducted the fuel relocation experiments. They focused on understanding of the fuel behavior and assessment of safety characteristics for the metallic fuel. Most of fuel relocation experiments were conducted in an open pool or a single-pin structure. They were useful to provide fundamental knowledge. However, it is necessary conduct fuel relocation tests in actual fuel assembly geometry and transient condition to provide experimental database for validation of in-house code. In the present study, the fuel relocation experiments were conducted in 19-pins bundle geometry. The objective of the study is to setup the experimental methods and understand thermal-hydraulic phenomena of fuel relocation. The Wood's metal was used as simulant for the metal fuel. Radiographic images were taken to observe frozen Wood's metal without any disturbance.