This paper investigates the changes in electrical and physico-chemical properties of lowvoltage power cables for nuclear application when subjected to the combined effects of gamma radiation and temperature. Electrical response is evaluated by means of the dielectric spectroscopy, while the physicochemical changes are analyzed at different structural scales through five complementary techniques (OIT measurements, FTIR spectroscopy, swelling measurements, DSC analysis and micro-indentation). The dielectric spectroscopy and the first two chemical techniques are shown to be appropriate for evaluating the development of radio-thermal ageing in low-voltage cables. Hence, the results reported in this article suggest the effectiveness of dielectric spectroscopy as a non-destructive technique for on-site cable diagnosis.

This study aims at investigating the blooming of Irganox 1076® onto the surface of a silane-crosslinked polyethylene. Preliminary studies on the commercial Irganox 1076® powder enabled to identify its crystalline structure and determine its main physico-chemical properties (characteristic IR absorption bands, melting properties, etc.). Then, the behaviour of Irganox 1076® in silane-grafted polyethylene was studied. Several films containing a concentration of Irganox 1076® ranged between 0.1 wt% and 2.1 wt% were characterized with FTIR spectroscopy and DSC. A peculiar attention was paid to the phase separation within the polymer bulk and the blooming of the antioxidant onto the polymer film surface. Then, this methodology was transposed to an industrial silane-crosslinked polyethylene containing at least 1 wt% of Irganox 1076® as in-service protective antioxidant. For this latter, optical microscopy was of great help for monitoring the blooming of Irganox 1076® onto the polymer film surface. In addition, the polymorphism phenomenon of Irganox 1076® was revealed by FTIR spectroscopy and DSC after thermal treatment at 70 C under vacuum.