In this paper, the defects caused by the currently dominant degradation mechanism (ODSCC at tube support plates) are statistically analyzed. The main results of the analysis include the status and predictions of:

• Number of defects;

• Distribution of defect sizes;

• Initiation and growth rates of defects.

The expected survival time of defects is studied in some detail. It is namely observed that a considerable amount of detected defects survive a few inspection cycles before they exceed the allowable size at which the tube is repaired.A special emphasis is given to the development and survival times of multiple defects on a single tube, especially at the lower support plates where a possibility of sleeving exists

Based on the results of statistical analysis, some predictions are given concerning the remaining lifetime of the steam generators. Those predictions also include other types of observed defects and may contribute to the optimum performance of the plant until the replacement of steam generators.