Statistical analysis of steam generator tube lifetime and probabilistic method for tube bundle inspection

Optimization of PWR 900 Steam Generator tube bundle in service inspection programs is developed from probabilist analysis of the results of checks carried out on equipment in service in France since 1977. After classifying the different types of defect observed, and grouping the steam generators by family, various statistical analysis methods are used to model tube failure distribution, applying the Weibull distribution function. A probabilistic method for selecting a sampling and inspection plan is then established, according to the specific statistical properties of each potential degradation zone, with a first plan to reveal the beginning of a degradation process, and a second plan to control and limit the number of degraded and defective tubes in each steam generator. (author)