Influence of Gamma Irradiation on Electric Cables Models: Study of Additive Effects by Mid-Infrared Spectroscopy
Abstract
Cables, especially their insulation and jacket materials made of polymers, are vulnerable to
ageing degradation during normal operation. However, they must remain functional for the entire
life of a nuclear power plant, or even in the event of an accident for cables with a safety requirement.
This study focuses on models of crosslinked polyethylene (XLPE)-based insulation of cables and
deals with the structure modification and the behavior of XLPE for nuclear applications due to the
effect of additives. Various additives are added to the polymer formulation to evaluate their impact
on ageing. The samples are irradiated at room temperature by several gamma doses, up to 374 kGy,
with two dose rates (40 Gy/h and 300 Gy/h) and compared with a non-irradiated sample used as
reference. To understand the impact of gamma irradiation on the materials, the principal component
analysis (PCA) method is applied on spectra recorded through attenuated total reflectance–Fourier
transform infrared (ATR-FTIR) spectroscopy. The results highlight the effects of ageing depending on
the dose rate and on the formulation of the materials, with the identification of different degradation
products. A curve resolution study compares the effects of different additives on polymer oxidation
and shows that the low dose rate leads to a higher degradation than the high dose rate.
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