Tensile properties of the NLF reduced activation ferritic/martensitic steels after irradiation in a fast reactor spectrum to a maximum dose of 67 dpa

The NLF series of steels are reduced activation ferritic–martensitic (RAFM) steels that are a part of the Japanese program to produce a suitable reduced activation ferritic–martensitic steel for the ITER project. Published reports on the NLF steels after about 35 dpa at 400 °C by Kurishita et al., indicate that these steels have similar strength and better ductility than other RAFM steels such as the JLF steels and F82H irradiated at 400 °C to similar doses. The tensile properties of NLF steels irradiated at ∼400 °C to doses as high as 67 dpa are presented here. Tensile tests were conducted at a strain rate of 5 × 10−4 s−1 at 25, 400 °C, and 500 °C. Variations in irradiation temperature in the range of 390–430 °C had a relatively small, but definite effect on the tensile properties for tests conducted at 25, 400, and 500 °C. The strongest hardening is observed for specimens irradiated at 390 °C, and very little hardening is observed for specimens irradiated at 430 °C. Strain rate jump tests were performed on NLF-0 and NLF-1 at 400 °C after irradiation to 52 dpa. The rate sensitivity, m, is quite low, 0.003–0.005 and does not appear to be affected by irradiation at 52 dpa for an irradiation temperature of 430 °C.