Studies on plant aging of light water reactors using the Fugen NPS

Ebine, Noriya 

In order to provide the technical information for the safety regulation on the aging management technical evaluation for the current commercial light water reactors (LWRs), wall thinning of the steel piping and verification of the countermeasures against SCC using the served materials of "Fugen" Power Station retired after 25 years operation have been investigated. Reliability of the wall thinning rate of the steel piping was examined referring the inspection data and the predicted calculations. Using these results, wall thinning data base was established. The validity of the management of pipe wall thinning at Fugen was examined. For SCC, there was no observed crack by metallurgical structure observations and ultrasonic inspections. It was thought that SCC was controlled judging also from the measurements of residual stress and the analysis of heat affected zone. The effectiveness of SCC management techniques at Fugen was examined.