Life performance of an EPR-insulated power cable exposed in service beyond 3 MGy in high-level radiation area

Abstract Mechanical and electrical test results are reported for a power cablethat has been installed for three and a half years in a high-level radiation area at the European Organization for Nuclear Research (CERN). The degradation of selected mechanical properties as a function of absorbed doseis compared with results of a short-term irradiation in a nuclear reactor. The tensile test specimens have been taken from the ethylene propylene rubber insulation and the polyvinyl chloridesheath material of the cable after exposure in service. For the measurement of breakdown voltage, short portions of insulated cable have been used. The aim of this work was to verify that the combined functional and environmental stress factors did not lead to more damage of the cable than was expected from the value of absorbed dose, and eventually to predict more precisely the service life of similar cables. The ratios of doses after service and short-term irradiation at 50% reduction of elongation at break were about 0.5 for the insulation and 1.0 for the sheath material at a dose of about 1 MGy. However, the breakdown voltagedid not show any significant variation in the dose range covered up to 3.6 MGy. Therefore, a safe lower dose limit may readily be derived from accelerated tests, but the margin until failure in service remains to be determined.