In this study, a novel alloy of modified Inconel 718 produced by laser powder bed fusion is studied before and after in-situ Kr irradiation up to 3 dpa at 200 and 450 degrees C. Before irradiation, the microstructure consists of dislocation cells having a misorientation angle less than 5 degrees and with an average size of -500 nm. There are also second phase particles of MC type carbides, Laves phase and oxides such as Y-O, Y-(Ti)-Al-O. While the microstructure consists of stacking fault tetrahedra, faulted and perfect loops after irradiation at 200 degrees C, dislocation loops are the primary defects at 450 degrees C. With increasing dose, the size of the defects remains similar at 200 degrees C while it increases at 450 degrees C. This has been attributed to the existence of vacancy type defects at 200 degrees C and the different defect transport mechanisms at different temperatures. Moreover, matrix and second phase particle compositions seem to be similar after irradiation. The sink strengths of the structures have been calculated and superior radiation resistance of this alloy has been attributed to the existence of fine cell boundaries stabilized by the second phase particles produced by additive manufacturing.