Abstract: Focusing on the notable radiation swelling deformation of metallic pellet,a tightly coupled multi-physics numerical model for fuel rod has been proposed and employed in a Numerical Fuel Rod code YUAN,which integrates neutronics,thermal-hydraulics and mechanics,and etc.based on unique floating finite element grids,to model the coupled fuel rod behavior of thermal conduction,mechanical deformation,neutron transport and isotopes depletion of fuel pellet/cladding.Typical metallic fuel is simulated by YUAN,and the deformation-caused multi-physical effects on thermal conduction and neutronics is analyzed.