Irradiation creep behavior of V-4Cr-4Ti alloys irradiated in a liquid sodium environment at the JOY fast reactor

Irradiation experiments on V-4Cr-4Ti alloys with sodium-enclosed irradiation capsules in the JOYO fast reactor were conducted using pressurized creep tubes (PCTs). The irradiation creep strain was significantly larger than the thermal creep strain below 686 degrees C, but there was no swelling of the neutron-irradiated V-4Cr-4Ti alloys. At temperatures below 500 degrees C, the irradiation creep was found to be proportional to the square root of the neutron dose and linear with the stress level. Above 500 degrees C, it was expected to be proportional to the stress level to a power greater than unity, because the irradiation creep mechanism could change from the stress-induced preferred absorption mechanism (SIPA) to the preferred absorption glide mechanism (PGA). By comparing annealed PCT specimens with cold-worked specimens, the cold-worked V-4Cr-4Ti alloys exhibited a larger irradiation creep strain compared with the annealed alloys. The irradiation creep compliance of the V-4Cr-4Ti alloys were 10 x 10(-6) MPa-1 dpa(-1) below 500 degrees C and 50-200 x 10(-6) MPa-1 dpa(-1) above 500 degrees C, a value greater than that of commercial V-4Cr-4Ti alloys, austenitic steels and ferritic steels. 2013 Elsevier B.V. All rights reserved.