Abstract
Nuclear power plants (NPPs) are operating beyond their original 40-year operating lifetime, with more than 80% operating on the first license renewal for an extended 20-years. To sustain the effective and cost-effective operation of their electrical cables, understanding cable material performance in current and future environments can lead to effective maintenance strategies and condition monitoring protocols. Addressing the issue of long-term operation and viability, accelerated aging was carried out on chlorosulfonated polyethylene (CSPE) / ethylene propylene rubber (EPR) insulations that were removed from harvested electrical cables. Cables were obtained as part of the Light Water Reactor and Sustainability (LWRS) Zion Harvesting Project in cooperation with Energy Solutions and the U.S. NRC. Zion NPP was in operation for 25 years prior to decommissioning before its 40-year operation license had expired.
For the Boston Insulated Wire (BIW) manufactured EPR insulation with outer CSPE jackets, degradation was observed in mechanical properties with respect to time and temperature was observed. This degradation was impacted by the outer CSPE jacket as the increase in to the time to degradation at the same temperature was observed for EPR insulations with the outer CSPE jacket removed prior to aging. The correlation of IM and density to EAB also suggested that these parameters could also be used effectively in the estimates of activation energy with additional data. Arrhenius analysis on the mechanical degradation as measured by EAB for the two types of BIW EPR insulations with outer CSPE jackets estimated activation energies slightly different (BIW-A without outer CSPE jacket 1.58 eV, BIW-B with outer CSPE jacket 1.10 eV) than the 1.24 eV found in from analysis of EAB data found in Zion NPP BIW insulation documentation. These values were higher than those previously reported of 0.90 eV to 0.96 eV for CSPE and EPR materials in the literature and additional measurements are needed to further validate the increase in activation energy for these harvested materials and possible impact on remaining useful life estimation. Finally, FTIR analysis showed differences in the oxidation as measured by decrease in C-H bonds in EPR insulation and CSPE jackets and increase in C-O bonds in certain cases.
