Behaviour of a PWR vessel dissimilar metal weld during a steam line break transient

This paper presents the results of a Finite Element analysis conducted on the behaviour of a 15 mm deep fully circumferential crack on the outer surface of a bi-metallic weld of a 900 MWe Pressurized Water Reactor vessel, during a Steam Line Break transient. The typical weld considered connects the stainless-steel hot leg with the ferritic vessel. This work is part of a Benchmark exercise organised in the framework of an European Commission (DG Environment) project on Transition Welds. However, the results presented here concern only those obtained at Framatome using SYSTUS + code and deal with the thermo-mechanical analysis, the evaluation of the crack driving energy (J-integral) and a discussion on crack stability. These results are compared with those obtained using a simplified method developed earlier and presented at one of the international conferences.