[en] The widespread use of nuclear technology has made the study of the effects of ionizing radiation on materials a very important topic, not only for applications in nuclear power plants, but also in radioactive waste disposal, fuel reprocessing plants and related research facilities. Materials based on organic polymers are widely used in nuclear technology because many advantages make them attractive for various applications including cable materials, coatings, seals, containers and many others. Polymers are used extensively as insulation and jacketing materials for cables. Cable integrity is of particular importance where safety instrumentation is involved. The condition of polymer-based cable materials can be best characterized by measuring elongation at break of their insulating materials. From practical point of view, the use of differential scanning calorimetry technique and of density gradient column technique is available for assessment of the cable lifetime. The results obtained with cables used in nuclear power plants are presented. (author)