Radio-Oxidation of Electric Cabled Models: Ageing Evaluation at the Atomic Scale

Abstract

The functionality of electric cables, being the safety components of plants, has to be ensured. In nuclear power plants, when they are in the reactor building, these cables can suffer γ irradiation even in normal operating conditions. Their ageing behaviour needs to be well understood to be able to determine a precise end-of-life criterion. As polymers are the most radiosensitive material of the cables, this paper focuses on the ageing of this kind of material and, more specifically, on the ageing of silane-crosslinked polyethylenes (XLPEs). XLPEs are now one of the most employed polymers to manufacture cables. We performed irradiation under oxidative conditions of several model silane-crosslinked polyethylenes with different additives and filler: at three different doses (0, 67, 220 and 374 kGy) for one dose rate (78 Gy·h−1) and at one dose (67 kGy) for three dose rates (8.5, 78 and 400 Gy·h−1). Modifications in the organic materials were followed by X-ray photoelectron spectroscopy. This analytical technique allows following the evolution of the different chemical products formed under irradiation. A better understanding at the atomic scale of the effect of additives on the degradation of polymers is proposed as a function of the ageing conditions.

Keywords

• formulated polyethylene
• γ irradiation
• radio-oxidation
• antioxidants
• flame retardant
• dose effect