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.