Steam Generator Tube Integrity Assessment Using a Probabilistic Approach

摘要

The rupture of a steam generator tube is one of the accidents that affects availability and safety of nuclear plants. Tornreduce the probability of occurrence of this problem, the utilities have implemented a maintenance program that consists inrninspect the tubes by eddy current test (ECT). The dimensions of the possible defects are compared with specified limits, andrnin case of non-compliance, the tubes are removed from service (plugged). Data from several plants in the world indicate thatrnthe initiation and propagation of the crack is due to stress corrosion cracking (SCC). The international experience shows arngrowing number of tubes removed by damage caused by SCC. As similar tendency has been verified in Angra 1 NuclearrnPower Plant, it turned out to be necessary to develop an action plan to manage the life of the steam generator. One of thernobjectives of this plan is to define the maintenance program that allows extending the residual life of the equipment. Therninitial results, restricted to the activities related to the structural area, are presented in this work. The approach for the analysisrnconsiders the technology of probabilistic fracture mechanics and aims to: a) define the statistical distribution of the mainrnparameter involved in the problem; b) establish an approach of plugging that allows the tubes to be longer in service withoutrncompromising the safety of Plant.