Life prediction of electrical cable equipment EPR insulating material

Cables in nuclear power stations are submitted to thermal and radiation stresses in their operating conditions. A study of the respective influences of temperature and radiation affords an accurate appreciation of the degradation processes of the insulating cable materials (EPR : ethylene propylene rubber). However, to be completely comprehensive, the study takes into account of the effects of the combined stresses irradiation-temperature. The main processes of degradation of these materials were studied by analysing sensitive properties to aging. In order to predict long-term behaviour, particularly beyond 30 years, we attempted to devise a prediction model based on the variation of the ultimate elongation, the most sensitive criterion to aging. The conclusions of the study suggest the degradation of the EPR as electrical cable insulators is low in nuclear power station environment after 50 years. This study provided an opportunity to predict the behaviour of the ultimate elongation versus time, temperature and irradiation. The originality of this research is based on the fact that it was possible to quantify the synergy effects on the basis of the analysis of the rate constant determined by the kinetic model