Master curve characterization of the fracture toughness in unirradiated and irradiated RPV steels using full- and 1/3-size pre-cracked Charpy specimens

Cleavage initiation fracture toughness (K(JC)) tests have been performed with full-size (10 x 10 x 55 mm³) and 1/3-size (3.3 x 3.3 x 18.3 mm³) pre-cracked Charpy (PCVN) specimens in the transition temperature region. IAEA reference reactor pressure vessel (RPV) steels, JRQ and JFL, and Korean SA508-3 forging steels were used in this study. Some specimens were irradiated to a neutron fluence of 4.5 x 10¹⁹ n/cm² (E > 1 MeV) at 288°C. For the JRQ steel, the transition temperature shift (ΔT₀) due to neutron irradiation is about 134°C from PCVN testing, which is greater than ΔT(41J) from the conventional Charpy impact testing. However, in a modern RPV steel, the transition temperature shift was almost negligible. The reference temperature T₀ values showed some dependence on the test temperature and specimen geometry, while the median and probabilistic bound lines of the Master Curve well described the population of the measured fracture toughness data. In general, the deviation of the measured T₀ values from different test conditions was about 10-15°C. Compared with the full-size PCVN data, the 1/3-size PCVN specimens may also give a reasonable result if the test conditions are adequately selected. (C) 2000 Elsevier Science Ltd. All rights reserved.