The change of fracture toughness of martensitic steels after irradiation in SINQ target-3

Abstract Small bend specimens of martensitic steels T91, F82H and Optimax were irradiated in SINQ target-3 up to about 9 dpa in a temperature range of 100–250 °C. The single specimen method was used to determine the J -integral values. The specimens were tested in a temperature range from room temperature to 250 °C, mostly at irradiation temperatures. The results showed that the fracture toughness of the martensitic steels decreased with increasing irradiation dose. Specimens tested at the irradiation temperatures and 250 °C indicated that the fracture toughness of all three martensitic steels remained above 100 MPa m 1/2 . One T91 specimen irradiated to 4.3 dpa tested at room temperature was totally brittle and broke in the elastic deformation region. The fracture toughness value was only about 28 MPa m 1/2 , within the lower shelf of the fracture toughness. There was no obvious difference in the fracture toughness of the steels after irradiation.