A PRACTICAL METHOD BASED ON STRESS EVALUATION (SIGMA(D) CRITERION) TOPREDICT INITIATION OF CRACK UNDER CREEP AND CREEP-FATIGUE CONDITIONS

The behavior of defects like cracks in nuclear components operating at high temperature, where creep is significant, must be under control. There exists the need to have a practical method of analysis, which ca n be used by engineers, to calculate the time of initiation for defect s existing at the start of life of nuclear components. This study pres ents the background, the development, the application, and results con cerning validation work made for a simplified method named sigma(d) of prediction of initiation for nuclear structures made of 316L austenit ic steel and operating at temperature where creep is significant. This method relies on the evaluation of real stress-strain history on a sm all distance d (d = 0.05 mm) close to the crack front and material cha racteristics (limiting stresses) that are available in nuclear codes l ike ASME Code cases or RCC-MR.