Radio-Oxidation Ageing of XLPE Containing Different Additives and Filler: Effect on the Gases Emission and Consumption

Abstract

In the lifetime extension of nuclear power plants (NPPs) context, aging of electric cables has to be very well understood in order to predict their end-of-life and thus to replace them on time. Therefore, evaluation and understanding of the ageing mechanism of the cable insulating material is mandatory under conditions as close as possible of those encountered in NPPs. In this context, different formulated crosslinked polyethylenes (XLPE)—one of the polymers used nowadays to manufacture the insulator layer—have been irradiated under oxidative conditions, at two different dose rates and at different aging doses. Gases emitted and consumed from the irradiated polymers were quantified to identify the primary processes happening in the materials and thus the interactions involved between the different molecules composing the formulated polymers.

Combining Experimental and Theoretical Tools to Probe Radio-Oxidation Products in Polyethylene

“…Ampoules were evacuated using a vacuum line and then filled with reconstituted air (20.0% O , 77.99% N , 2.01% Kr), with krypton being used as a tracer to determine the final pressure. Pictures of similar samples in their glass containers can be found in a previous paper [ 30 ]. At the end of the irradiation, sample masses were estimated to contain a final H content of about 1 vol%.…”

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

“…Samples were furnished by Nexans France under the form of tapes of about 500 µ m thick. In this work, different formulations (with the same nomenclature as proposed in a previous paper [21]) were evaluated: • secondary antioxidant Irganox PS802 (chemical formula given Figure 1B) • flame retardant ATH (aluminium trihydrate, whose chemical formula is Al(OH) 3 ).…”

“…Samples were furnished by Nexans France under the form of tapes of about 500 µm thick. In this work, different formulations (with the same nomenclature as proposed in a previous paper [21]) were evaluated:…”

“…Synthesis of crosslinked polyethylene XLPE has already been presented in a previous article [21]. The LLDPE chosen for this study has a density of 0.918 g•cm −3 , a melting point of 120 • C and contains a very small quantity of antioxidants (mainly BHT and Irganox 1076 [28]).…”

“…Keeping this objective in mind, the purpose of this article is to obtain a deeper knowledge on polymers ageing in conditions representative of those encountered in NPPs (50 • C and 0.1 Gy•h −1 in the reactor building during normal operations). To complete a series of studies [21][22][23][24][25][26][27], we decided to evaluate the ageing of different silane-crosslinked polyethylenes (XLPEs) at the atomic scale. To understand the role of each additive on the ageing mechanisms, formulated model XLPEs with an increasing number of added additives and fillers were irradiated under oxidative conditions at three different doses for one dose rate and at one dose for three dose rates.…”