LIMIT LOAD ANALYSIS AND SAFETY ASSESSMENT OF AN ELBOW WITH A CIRCUMFERENTIAL CRACK UNDER A BENDING MOMENT

The use of the leak-before-break concept in the design of a Primary He at Transport (PHT) piping system for nuclear power plants requires pos tulation of the largest credible flaws at highly stressed points and d emonstration of system stability under the most severe loading conditi ons. In the PHT piping system, the elbows and branch tees are normally found to be among the most highly stressed piping components. This ne cessitates detailed flaw evaluation of these components. In the presen t paper, safety assessment of a pump discharge elbow of 500 MWe Indian PHWR with a throughwall circumferential crack under a bending moment is carried out using the R6 approach. The stress intensity factors (SI F) have been computed by using a database of SIF for elbows with crack s which was generated in one of our recent studies. Limit loads at pla stic collapse have been evaluated by carrying out non-linear finite el ement analysis. Finally, the safety assessment of the pump discharge e lbow is performed by doing a sensitivity study on crack length, applie d moment and material fracture toughness.