To describe the deformation and radiation aging of metallic materials by means of elastic-plastic models, the effective time is introduced and the corresponding equations of theory plasticity with isotropic and kinematic hardening are formulated. Much attention is given to the description of the effect of radiation swelling, and changes of the yield stress due to deformation and radiation aging. The theoretical relations are received and the numerical calculations are carried out. These relations are compared with the results of the yield stress changes of different alloys during the deformation and radiation aging. The important problem of embrittlement of metallic materials is also discussed. Traditionally the value of relative deformation and the value of relative changes of cross section area of a specimen at the fracture are used as embrittlement characteristics. As it is follows from our considerations the formal definitions of these parameters accepted in literature are not quite correct, so they can’t