Fracture toughness of irradiated modified 9Cr–1Mo steel

The effects of irradiation on fracture toughness of modified 9Cr–1Mo steel in the transition region were investigated. Half size precracked Charpy specimens were irradiated up to 1.2 × 1021n/cm2 (E > 0.1 MeV) at 340 °C and 400 °C in the Korean research reactor. The irradiation induced transition temperature shift for a modified 9Cr–1Mo was evaluated by using the Master Curve methodology. The T0 temperature for the unirradiated specimens were measured as −67.7 °C and −72.4 °C from the tests with standard PCVN (precracked charpy V-notch) and half sized PCVN specimens, respectively. The T0 shifts of specimens after irradiation at 340 °C and 400 °C were 70.7 °C and 66.1 °C, respectively. The Weibull slopes for the fracture toughness data obtained from the unirradiated and irradiated modified 9Cr–1Mo steels were determined to confirm the applicability of master curve methodology to modified 9Cr–1Mo steel.