[en] Auxilliary piping elbows of PWR reactors are assembled by longitudinal submerged arc weld of two halves. The elbows are made of ICL 167 CN similar to AISI 316. During fabrication and erection on site some of them have been cut and repaired because of lack of penetration, causing important costs and delays. The studies performed and presented here were conducted in order to evaluate the possible serious consequences of this defect and allow predicting for the future in case of existence of such defect in a weld: how it will cause a crack propagation and how it will be possible to detect and measure it from the outside. Tests have been performed on fatigue specimens cut in the weld of an elbow (with real defect, and with artificial machined crack) in air and PWR environment. (Auth.)