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