Superior Charpy impact properties of ODS ferritic steel irradiated in JOYO

The effect of neutron irradiation on Charpy impact properties of an ODS ferritic steel developed by PNC was studied. The miniaturized Charpy V-notch (MCVN) specimens (1.5 x 1.5 x 20 mm) of two orientations (longitudinal, called 1DS-L, and transverse, IDS-T) were irradiated to fluence levels of (0.3-3.8) x 10(26) n/m(2) (E-n > 0.1 MeV) between 646 and 845 K in JOYO, MCVN specimens before and after the irradiation were subjected to instrumented Charpy impact tests. The test results and fracture surface observations showed that in the unirradiated state the steel showed no ductile-to-brittle transition behavior until 153 K regardless of orientation and the upper shelf energy of the steel was as high as that of a high-strength ferritic steel without dispersed oxide. Such excellent impact properties were essentially maintained after the irradiation although an appreciable decrease in absorbed energy occurred by higher temperature irradiations at and above 793 K. (C) 1998 Elsevier Science B.V. All rights reserved.