Background: A core drop accident causes the core barrel and supporting structure to drop and impact on the bottom of the reactor vessel.Purpose: To ensure the scram functionality is maintained.Methods: The stress-strain curves applicable to the material are approximated by Ludwik’s expression.Considering the core deadweight

buoyancy force and heat expansion

material train ratios for both cold and hot conditions are calculated.Results: Vessel impact load（8294482N in cold condition & 6064537N in hot condition） is determined

which remains within the vessel design specification limits.The calculated drop length（47.44 mm in cold condition & 27.63 mm in hot condition） is less than the fuel pin full-diameter engagement length

so the fuel assembly top nozzle will remain engaged during a core drop.Finally the compressive assemblies are evaluated

which would not buckle due to the core drop accident loads.Conclusions: A core drop will not affect the scram function.