Frequency Domain Spectroscopy Analysis of EPR/CSPE Insulated Nuclear Power Plant Cable Samples Subjected to Irradiation Ageing and Combined Irradiation and Mechanical Ageing

Although the share of renewable sources is increasing in electrical energy generation, nuclear power plants (NPPs) still produce 10% of the total electricity worldwide. In addition, the lifetime extension of the existing fleet of NPPs has a crucial role in the cost-effective path to the decarbonisation of the electricity sector [1] . Long-term, safe operation of nuclear facilities relies on safety-related equipment, including cables, which have to fulfil their function in normal operation and all postulated events during their qualified lifetime [2] . The cables of nuclear facilities are exposed to many stressors ( Figure 1 ), causing chemical reactions such as oxidation, cross-linking, and chain scission in their polymeric insulation and jacket materials [3] , [4] . These processes cause the degradation in the chemical, mechanical and electrical properties of polymeric components of the cable, leading to loss of functionality. Traditionally in the nuclear industry, 50% of elongation at-break (EaB) is accepted as the end-of-life criteria for insulating polymers [5] . However, the measurement of EaB is also widely applied for determining the remaining lifetime, even though this is a destructive technique [6] , [7] .