Preliminary results of electric insulation void content growth fromsimulated exposure to a nuclear power plant's high energy line breakevent

摘要

A need exists to confirm the remaining life of electric cable usedin nuclear power stations. Remaining life must include margins forsurviving the potential harsh environment effects of a design basisevent (DBE) after up to 60 years of normal operation. Typically a DBEwould be a postulated break in the largest high temperature pressurizedline leading to elevated temperatures (accelerated aging conditions) inthe surrounding environment. Previous research has shown that voidcontent within polyolefin electric insulation grows during normalthermal aging and that oxygen diffusion plays a role in this growth.Under accelerated aging conditions, oxygen diffusion is limited reducingchemical reaction rates, and potentially affecting the aging process.This paper discusses preliminary experimental results indicative ofaccelerated aging for three commonly used polyolefin materials. Eachsample was re-examined after thermal annealing for 17 hours at 120 C.Results indicate the void content increased dramatically from thepre-aged sample values