Postirradiation tensile behavior of nickel-doped ferritic steels

Tensile specimens of normalized-and-tempered 9Cr-1MoVNb, 9Cr-1MoVNb-2Ni, 12Cr-1MoVW, 12Cr-1MoVW-1Ni, and 12Cr-1MoVW-2Ni were irradiated in the Experimental Breeder Reactor (EBR-II) at 390, 450, 500, and 5500C to displacement-damage levels of approximately 16 dpa. The nickel in these steels was added to produce helium during irradiation in a mixed-spectrum reactor. Irradiation of these steels in the fast-spectrum EBR-II, where little helium is formed, helped determine the effect of helium on properties. The nickel-doped steels were stronger prior to irradiation due to a lower tempering temperature. After irradiation, the properties of the steels with and without nickel were similar, indicating that the presence of nickel did not affect the behavior of the steels during irradiation. These fast-reactor results indicate that it is feasible to use the nickel-doped ferritic steels to study helium effects. (orig.)