Sodium fire is one of the accidental events in case of sodium leak of sodium-cooled fast reactor. This event is basically the reaction between liquid sodium and oxygen with exothermic heat. The transport behavior of the aerosol as reaction product (sodium oxide) by sodium fire through the air duct between cells may cause damage and failure of the control devices and harmful effect against human body. Previously, many experimental works on sodium fire have been carried out in single cell. However, the finding on the sodium fire experiments using multiple cells is quite limited. Thus, the elucidation of aerosol transport phenomenon between cells is indispensable for validation of sodium fire analysis code.
In this study, in order to obtain the fundamental information on aerosol transport behavior between cells, the development of Multiple cells with Expandable connecting pipe Test (hereinafter referred to as “MET”) facility and related experimental devices have been carried out since 2016. The MET facility comprises 3 cells and several expandable connecting pipes and has the flexible cells arrangement capability for desired multiple cells layout. Also, the size of the cell was determined on the basis of Grashof number to simulate the condition of natural convection heat transfer in case of sodium fire. Each cell comprises 6 wall panels made of both acryl and matte black coating aluminum. For simulant of sodium fire aerosol, silica particle (approximately 2.2 g/cm3, 1μm) was used to simulate the density of sodium oxide produced by sodium fire and primary particle size of the aerosol based on the results obtained by in-situ measurement using laser diagnostics for sodium-oxygen counter flow in our previous work.
The preliminary experiments using 2 cells connected with horizontal or vertical pipe were performed to observe the particle diffusion and transport behavior. The stable particle supply was confirmed in the particle supply cell, and the basic feature on transport behavior between 2 cells was observed by using video camera. After experiment, the particle settled in the floor of each cell was collected and weighed. As a result, certain amount of particle sedimentation was detected in the adjacent cell, which is evident from observation of the particle diffusion and transport behavior. Thus, the basic feature on transport behavior and sedimentation of the particles in the MET facility were confirmed.