Abstract: Uranium nitride is an important candidate for Accident Tolerant Fuels（ATF） due to its high thermal conductivity and high heavy metal（HM） density. This paper introduced an enhancement of FUPAC by incorporating UN material property correlations and irradiation models. Some preliminary analyses of UN fuel performance at steady-states were also performed, and the results showed that UN fuel has good performance in aspects like fuel temperature, fission gas release, fuel rod pressure and cladding strain. Finally, future research and development works for UN fuel are discussed in this paper.