Reliability Assessment of Boiling Water Reactor Pressure Vessels Having Marshall-Type Initial Cracks
Date Issued
2010
Date
2010
Author(s)
Lee, Li-Chuan
Abstract
The reactor pressure vessel (RPV) is the most important pressure boundary component in a nuclear power plant. The failure of RPV will cause serious hazard, and the vertical welds of RPV attribute very high probability of failure. The failure probability of RPV in general increases along with time owing to crack growth in welds of RPV. The increase is even more significant when radiation embrittlement is taken into consideration. In the present study, Monte Carlo Simulation (MCS) and Probabilistic Fracture Mechanics are employed to study the reliability of a Boiling Water Reactor Pressure Vessel (BWRPV). It is assumed that a predominant initial crack exists in the vertical welds of the RPV. When subjected to environmental conditions, the crack grows which, in turn, increases the failure probability of the vessel. In the modeling and analysis, the initial crack distribution, crack growth mechanism, low temperature over pressurization (LTOP) transients, radiation embrittlement, NDT examination, renew process and uncertainty of material properties are all considered. The result indicates that the probability of failure (POF) of the analyszed RPV is 4.32×10-5 after 40 years of operation if non-destructive inspection is employed and renewal action is taken every 10 years. Under the same inspection and repair condition, the POF decreases to 5.94×10-5 after 60 years of operation. It reflects that the POF of BWRRPV can be reduced effectively through periodic inspections and complete repair actions afterwards.
Subjects
Reactor Pressure Vessel
Probabilistic Fracture Mechanics
Low Temperature Over Pressure
Crack Growth
Radiation Embrittlement
Reliability
Type
thesis
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