Static Stress Analysis of Steam Generator Shell Nozzle Junction for Leak Before Break Analysis

Abstract

The present power scenario in India is characterized by major contribution from fossil power stations. Under these circumstances, introduction of Fast Breeder Reactors (FBR) on commercial scale is possible only if their economic competitiveness is demonstrated viz-a-viz fossil power stations. For Sodium Fast Reactors, the Steam Generator is known to be a key component in terms of competitiveness and plant availability with safety implications through the sodium/water reaction. One of the critical locations in SG is the shell nozzle junction. This junction is subjected to an end bending moment and internal pressure. Since the shell nozzle junction is the critical location of SG a double-ended guillotine rupture will result in leakage of large quantity of sodium, which is not desirable. Hence safety requirements demand that LBB criteria with assumed initial flaw have to be demonstrated. For all these analysis, the basic requirement is to predict the state of stress precisely in the shell nozzle junction under various loading conditions. An efficient finite element modeling for shell nozzle junction has been presented in which shell elements are employed to idealize the whole region. The stress and deformation values are presented and compare with experimental study. Based on these analysis, the crack is initiated at the intersection of straight vertical shell and the cone ie. at the pullout region. These results are used for the analysis of leak before break concept.