The examination results of nuclear power plants pipelines of large diameter show that the welded joints of the pipelines might contain many flaws located along the circumference of the joint. If the pipeline, the welded joint of which contains the detected flaw set, is planned to be allowed for further operation the necessity of the safe operation justification of the pipeline occurs. In accordance with requirements of the Russian federal standards and rules in the field of atomic energy use when justifying the safe operation of the pipeline, it is necessary to idealize the flaw in a form of ellipse when the flaw comes out on the surface of the welded joint or semi-ellipse otherwise. Since the flaws are located along the perimeter of the welded joint and at great distance from each other, idealization of the flaw set is impossible in compliance with normative documentation. A conservative method of idealization of a flaw set in circumferential welding of pipelines of nuclear power plants independently to relative position of the flaws is proposed. With this conservative approach to idealization of the flaw set, all the flaws are unified at one place forming a single large-size “supercrack”. All the necessary assumptions and mathematical description of the method are provided. Moreover, an example of application of the method and an example of failure possibility analysis of a pipeline containing a flaw set forming a single “supercrack” are given.
Keywords: flaw, crack, pipelines of nuclear power plants, welded joint, failure possibility.
Article language: Russian. Pp. 20–28. DOI: 10.26277/SECNRS.2021.100.2.002.
