In-reactor creep behavior of selected ferritic alloys

An experiment was conducted in the Experimental Breeder Reactor-II (EBR-II) to investigate the in-reactor creep behavior of selected ferritic alloys. Pressurized tube creep specimens fabricated from the following ferritic alloys: HT9, 9Cr-2Mo, and 2-l/4Cr-1Mo, were irradiated in EBR-II to a peak fluence of 2.8 x 1022 n/cm2 (E > 0.1 MeV) at irradiation temperatures of 443, 505 and 5720C. Each alloy had four specimens with midwall hoop stresses of 0, 50, 75 and 100 MPa at each irradiation temperature. Measurements of the zero-stressed specimens indicate that none of the ferritic alloys are exhibiting swelling or phase transformations at these irradiation conditions. In general, the measure creep strains from this experiment were small (less than 0.4%) except for the alloy 2-1/4Cr-1Mo at the highest temperature. The in-reactor creep strains for all ferritic alloys investigated were similar for irradiation temperatures of 443 and 5050C. At 5720C, 2-1/4Cr-1Mo shows a breakdown in its creep strength when compared to the other ferritic alloys which continue to exhibit good creep resistance. For these irradiation temperatures, the ferritic alloys are more resistant to creep when compared to 316 stainless steel