Three-dimensional simulation of fuel relocation during loss-of-coolant accidents based on the coupled FEM-DEM approach

•Three-dimensional simulation (3D) of fuel relocation under loss-of-coolant accident is performed by using discrete element method.•The 3D simulation of fuel relocation is firstly validated by the in-pile experiments.•The critical parameters like fuel stack reduction, mass fraction and filling ratio are influenced by the mean diameter of fuel fragments.•The exponentially fitting correlations are proposed for the fuel stack reduction as a function of the relative cladding volume increase.•The exponentially fitting correlations are proposed for the mass fraction and filling ratio as a function of the cladding circumferential strain.