• LBB
• leak before break
• PLBB
• probabilistic fracture mechanics

The Leak Before Break concept has gained considerable attentions in the past years, as the application of this criterion can reduce costs and facilitate inspections and maintenance procedures. The Leak Before Break argument consists in the demonstration that a trough-wall crack in a pressurized pipe will leak a detectable amount of coolant before it reaches the critical size. The objective of this work is to develop a better understanding of the parameters that influence the applicability of the criterion, the development of a probabilistic approach and a method for the optimization of deterministic safety factors. The deterministic model for the simplified leak before break procedure is implemented and validated; the model is then coupled with a probabilistic software and sensitivity and reliability analyses are carried out. Deterministic and probabilistic results are shown with the influence of the system parameters. A method for the optimization of the safety factors is developed and coupled with the deterministic and probabilistic analyses. Examples of possible results from the optimization are shown and compared with the NRC deterministic safety factors.