Service lifetime estimates for nuclear medium voltage (MV) cables in nuclear power plants often do not match the actual performance lifetime in service conditions, particularly under immersion. With the majority of submerged MV cable insulation in NPPs being EPR and XLPE, a study was done to determine thermally aged EPR lifetime. However, with 34 EPR insulation failures reported within 30 years of installation, their 300-year predicted lifetime does not match the later survey. Current lifetimes are estimated using various accelerated ageing tests mostly dry, but these tests are not tuned for the material in its specific application, which may experience a range of environmental factors that change the modes or kinetics of degradation. This paper outlines a testing procedure utilizing different environments to expand more accurate life estimates on the effects of cyclic and permanent immersion in water, Harrison solution, and copper sulfate on polypropylene and polyethylene at elevated temperatures. Current results after 16 weeks suggest immersion and cycling show greater UTS impact. After further analysis and more tests, this research will propose either a correlation between the lifetime estimate of dry-aged polypropylene and polyethylene to cycled and immersed polypropylene and polyethylene or advocate for additional time or research correlated with electrical properties.
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