Aging and Reliability Assessment of Recirculation Piping in Nuclear Power Plants
Date Issued
2008
Date
2008
Author(s)
Cheng, Yu-Liang
Abstract
Nowadays, we are facing problems of global energy crisis and the greenhouse effect. The advantage of low cost and small amount of discharge of makes life extension of existed nuclear power plants an important research topic. The first task of life extension of a power plant is the aging assessment of its components. And one of the most important components of a nuclear power plant is its piping systems. Therefore, in the present study, the aging assessment of reactor recirculation system of an existed nuclear power plant is assessed. In general, after a long period of operation, piping of a reactor recirculation system faces various aging problems that affect the safety of the plant. In the first half of the study, in consideration of fatigue crack growth, probabilistic fracture mechanics software PRAISE (Piping Reliability Analysis Including Seismic Events) is applied to find failure probabilities of welds of the system based on stress data of a BWR (Boiling Water Reactor) plant. The result shows that failure probabilities of welds range from to , and the difference is not significant when evaluated, respectively, after 40-year and 60-year of operation. It indicates that life extension of the system can be considered. In the second half of the study, a rather simple and convenient aging assessment model for the fatigue crack growth problem of nuclear piping is proposed. Like PRAISE, it is also based on the deterministic fatigue crack growth model and can be used to evaluate failure probabilities of piping welds through a probabilistic analysis. The calculated result indicates that failure probabilities of those studied welds are between and . They are compatible with but more conservative than those obtained by PRAISE. Therefore, if PRAISE is not available, the proposed method can be used for the aging assessment and failure probability estimation of a piping system.
Subjects
recirculation piping
failure probability
probabilistic fracture mechanics
Type
thesis
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