The lifetime extension of the nuclear power stations is considered as an energy challenge worldwide. That is why, the risk analysis and the study of various effects of different factors that could potentially represent a hazard to a safe long term operation are necessary. These structures, often of great dimensions, are subjected during their life to complex loading combining varying mechanical loads, multiaxial, with non-zero mean values associated with temperature fluctuations and also PWR environment.

The methodology for fatigue dimensions of the Pressurized Water Reactor components (PWR) (ASME, RCC-M, KTA, ...) is based on the use of design curves established from test carried out in air at 20°C on smooth specimens by integrating safety coefficient that covers the dispersion of tests associated with the effects of structures.

In the framework of fatigue design rules upgrading (RCC-M, RCC-MRx), the uniaxial reference fatigue curve was altered by taking into account effects like: Multiaxiality, Mean stress or strain, Surface roughness (polished or ground), Scale effect, Loading History. In addition to this effect, Environmentally Assisted Fatigue is also receiving nowadays an increased level of attention.

In order to take into account the effects of these aggravating factors, two experimental device are developed at LISN with same specimen geometry:

The first device (FABIME2) is to determinate the effect of equi-biaxiality and mean strain/ stress on the fatigue behavior of 316L and 304L-CLI austenitic stainless steel. A second and a new device (FABIME2E) based on FABIME2 is developed to study the impact of the environmental effect in the biaxial fatigue.

The first results obtained with this new test stand FABIME2E of biaxial fatigue in the PWR environment will be presented. Their numerical interpretations using the engineering methods, provide answers to the different aggravating effects of fatigue in the components of nuclear reactors.