On the Correlation of Crack Resistance Curves on Upper Shelf Energy for German RPV Steels

J-crack resistance (J-R) curves, numerically determined and based on correlation formulas with the upper shelf energy level (USE) of the Charpy transition curve have been compared with measured J-R curves for German RPV steels, determined from single specimen tests. The USE were determined as mean values of the results above 95% ductile fracture appearance, as available from usual application in irradiation surveillance programs and averaging the temperature effect. The J-R curves numerically determined by the Gurson material model give a good representation of the measured crack resistance curves and the application of the correlation with USE in U.S. NRC Regulatory Guide 1.161 results in enveloping approximations with conservativeness increasing with crack growth.