Comparative study on different methods for determination of activation energies of nuclear cable materials

During the design stage of a nuclear power plant, the qualification testing is obliged to be conducted on the electrical equipment like cables to ensure the reliability and to predict the service lifetime of them under the operational conditions. Thereinto, thermal and oxidative degradation of the cable insulations and sheaths that are made of polymeric materials is the priority concern, and the renowned Arrhenius model is always referred to, which consequently calls for determination of the imperative kinetic constant - the activation energy. Actually, diverse methods for activation energies have been established by the scientists and applied by the engineers, but consensuses still have not been reached for such a method that is both convenient and conservative, and for such value ranges that are both reasonable and representative. Hence, in this paper, totally five different testing and data processing methods including thermal ageing test, differential scanning calorimetry and thermogravimetry analysis were utilized to determine the activation energies of three domestic polymeric materials that are intended for nuclear cables of the advanced pressurized water reactors in China. The results were then collected and the reasons for the differences among them were discussed, based on which the advantages and disadvantages of these methods were compared, and finally a compromising approach was proposed. •Different methods for determining activation energies were reviewed, that is important for life prediction of nuclear cables.•Five prevailing testing and data processing methods were used to determine activation energies of three polymeric materials.•The activation energies determined from these methods were compared and reasons for the difference among them were discussed.•A balanced approach taking consideration of the advantages of each method was proposed for qualifying nuclear cables.•Achievement of this paper will help to optimize qualification testing and improve manufacturing of nuclear cables in China.