Analysis of a bending test on a full-scale PWR hot leg elbow containing a surface crack

EDF, in co-operation with Framatome, has conducted a large research programme on the mechanical behaviour of thermally aged cast duplex stainless steel elbows, which are part of the main primary circuit of French PWRs. One important task of this programme consisted of testing a full-scale PWR hot leg elbow. The elbow contained a semi-elliptical circumferential notch machined on the outer surface of the intrados, as well as casting defects located on the flanks. To simulate the end-of-life condition of the component regarding material toughness, it had previously undergone a 2400-h ageing heat treatment at 400°C. The test preparation and execution, as well as the material characterization programme, were handled by MPA. The test was conducted under constant internal pressure and in-plane bending (opening mode) at 200°C. For safety reasons, it took place at an open air-site: the Meppen military test ground. At the maximum applied moment (6000 kN m), the notch did not initiate. This paper presents the results of the experiment and the results of the fracture mechanics analysis, based on finite element calculations.