Analysis of heat transfer behaviors in EAGLE ID1 test using particle-based simulation method

In the EAGLE in-pile ID1 test, which has been performed by Japan Atomic Energy Agency (JAEA) to demonstrate early fuel discharge from a fuel subassembly with an inner duct structure (FAIDUS), it was deduced that observed early duct wall failure was initiated by high heat flux from the molten pool of fuel and steel mixture. The posttest analyses suggest that pool-to-duct wall heat transfer might be enhanced effectively by the molten steel in the pool without the presence of fuel crust on the duct wall. In the present study, mechanisms of effective heat transfer from the molten pool to the duct wall was analyzed using a fully Lagrangian approach based on the finite volume particle (FVP) method for multi-component, multi-phase flows. Material distribution as well as steel droplet size in the molten pool after its formation was considered as parametric simulations. The present 2D particle-based simulations demonstrated that large thermal load that leads to early duct wall failure can be caused by local contact of molten steel to the duct wall as well as discrete formation of fuel crust on the duct wall.