Dynamic Elastic-Plastic Behavior of Circumferential Cracks in a Pipe Subject to Seismic Loading Conditions

Abstract

An analytical study is performed to investigate the structural stability, and inherent integrity, of a Pressurized Water Reactor primary coolant loop cold leg pipe containing a through-wall circumferential crack. The purpose of this study is to gain a better understanding of the mechanisms and extent of crack opening behavior in a real piping system, and, thus, establish the basis for improved pipe break criteria. Cracks extending one-half the circumference or greater are considered in the pipe. Combined operating pressure plus external seismic loads are applied simultaneously to cause a maximum crack opening effect. A dynamic elastic-plastic analysis is performed to calculate stress intensity factors at the crack tip. The results are compared with experimental fracture toughness data to assess the material’s capability to resist crack extension. A fatigue crack growth study is also performed to determine the range of initial flaw sizes which could grow and extend during normal operation to threaten the integrity of the cold leg pipe.