[en] X-ray and neutron diffraction studies were performed on nonstoichiometric α-U₂N_3+X having a composition range 1.68< N/U<1.84. It was confirmed that the crystal structure of α-U₂N_3+X in this composition range was a distorted Mn₂O₃-type structure. Structure parameters of U and N atoms were determined. Results showed that the positions of U atoms varied continuously with increasing nitrogen content. No evidence of the modification from bcc to fcc could be obtained. Interatomic distances of U-U and U-N were calculated. The position parameter of N atoms showed that the position of N atoms slightly deviated from the tetrahedral site. (orig.)