[en] In order to simulate the behavior of a circumferential crack in a RPV-cylinder wall under pressurized thermal shock (PTS) conditions a large plate made of RPV-steel 22NiMoCr37 was tested under four point bending. The depth of the surface crack was 35% of the wall thickness with a c/a-ratio of 2.5. J_R-curves for the material were measured from side-grooved and smooth CT-specimens of different dimensions. The aim of the test was to achieve crack initiation and some amount of ductile crack growth and to verify ductile fracture mechanics analysis and assessment methods, including the transferability of material parameters measured on small-scale specimens to the plate. Therefore, analytical and three-dimensional elastic-plastic finite element analyses had been carried out to predict and to simulate the initiation and stable crack growth. Based on the J-integral concept the agreement between the experiment and the numerical simulation was improved if open-quotes constraint-modifiedclose quotes J_R-curves were taken into account. 7 refs., 13 figs., 2 tabs