Evaluation of HDR cyclic thermal shock tests

The growth of a surface crack in a pressure vessel nozzle under thermal fatigue is discussed comparing theoretical predictions with experimental results from NDT-measurements. The temperature and the thermal stress distributions were calculated using two 2D-FE-analyses with different thermal boundary conditions. Plastic deformations were approximately taken into account. Two different calculational procedures allowing for two-dimensional stress distributions in the region of the crack surface are used to evaluate stress intensity factors for a semi-elliptical surface crack. Good agreement between the two procedures is achieved. The results of crack growth calculations depend strongly on the thermal boundary conditions and are also showing the importance to consider plastic deformations near the cooled nozzle surface. Reasons for the disagreement between theory and experiment are discussed. (orig.)