An approach to the probabilistic justification of a leak before break concept and break elimination for VVER secondary circuit pipelines

The paper describes a methodology for calculating break probability and the applicability of a leak-before-break (LBB) concept for the secondary circuit pipelines at nuclear power plants with VVER reactors. As well as a calculation based on the LBB concept, an example of break elimination using probabilistic approaches is presented. The study was carried out on the feedwater and main steam pipelines of an AES-2006 project. As well as taking into account the known defectiveness, data setting used a calculation method in the absence of such information. An example of calculating secondary circuit pipelines using experimentally obtained defectiveness data is presented. The leak probability for various nominal crack diameters is provided taking into account the detection of cracks during non-destructive testing, as well as cases of non-detection.