S3{112} grain boundary (GB) is known to exhibit plastic slip in bcc metals, which overall contributes to the good ductility and toughness of such metals as iron, matrix element for the steels applied in nuclear industry. During nuclear operation, the neutron irradiation causes formation of point defects and their clusters which lead to the non-equilibrium mass transport and agglomeration of nanoscale defects inside grains and near the grain boundaries. Due to the effect of chemical segregation, GBs can encounter sessile obstacles preventing the GB plastic slip. Understanding the influence of the irradiation defects segregated at the grain boundaries is important for the development of structural steels for nuclear fusion and fission applications. The present paper studies the influence of the irradiation defects, such as Cr precipitates, He bubbles and voids on the plastic slip of the GB interface. The studied defects are found to act as strong obstacles to the glide of the elementary disconnections responsible for the shear-coupled GB migration. The interaction between a single elementary disconnection and a series of them provided by a source has been studied. As a result of the interaction with impenetrable defects the formation of residual defects such as loops is observed.