Design and Verification Testing for Metallic Fuel Relocation Experiments with Pressure Injection in a Pin Bundle Core Structure of a Sodium-Cooled Fast Reactor

摘要

A pool-type sodium-cooled fast reactor (SFR) using metallic fuel has a number of inherent safety features that may support benign consequences for design basis accidents (DBAs). Even in postulated severe accident conditions, the molten core is designed to remain under sub-critical condition in a passive coolable geometry. Partial core melt down of Experimental Breeder Reactor-1 (EBR-1) provided some evidence of fuel relocation and dispersion behavior in a postulated severe accident. In the case of the postulated severe accidents in SFRs, relocating fuel in the active core area along the coolant channel is an important negative reactive feedback factor that lowers the reactor power level and consequently eliminates the possibility of recriticality. Therefore, understanding the relocation behavior of fuels and the coolability of the relocated fuels in the postulated severe accident is one of the most important factors in the safety assessment of SFRs. Research has continued to understand the relocation behavior of metallic fuels under the postulated severe accidents [1-13]. Early work focused on fragmentation behavior of molten metallic fuels in an open sodium pool and revealed high porosity of the fragmented fuels [1-7]. Recently, studies have been conducted on the relocation behavior of the metallic fuels in the realistic core channels [8-13]. Kim et al. studied the relocation behavior of the metallic fuel in single pin core structures using the Argonne's Metallic Uranium Safety Experiment (MUSE) facility [11, 12]. The relocation behavior of the metallic fuel was then investigated using pin bundle test sections in the MUSE facility. The pin bundle test sections were fabricated as a mock-up of the fuel assembly of the prototype generation-IV sodium-cooled fast reactor (PGSFR) which is developed by Korea Atomic Energy Research Institute (KAERI) [13]. This study showed that the relocated metal fuel could have a porous medium even in a pin bundle geometry.