The effect of neutron irradiation on vanadium alloys

Abstract

Neutron-irradiated vanadium alloys were evaluated for their susceptibility to irradiation hardening, helium embrittlement, swelling, and residual radioactivity, and the results were compared with those for the austenitic and ferritic stainless steels. The VANSTAR-7 and V-15Cr-5Ti alloys showed the greatest hardening between 400 and 600°C while V-3Ti-Si and V-20Ti had lower values that were comparable to those of ferritic steels. The V-15Cr-5Ti and VANSTAR-7 alloys were susceptible to helium embrittlement caused by the combination of weakened grain boundaries and irradiation-hardened grain matrices. Specimen fractures were entirely intergranular in the more severe instances of embrittlement. The V-3Ti-1Si and V-20Ti alloys were most resistant to helium embrittlement. Except for VANSTAR-7 irradiated to 40 dpa at 520°C, all of the vanadium alloys exhibited low swelling that was similar to the ferritic steels. Swelling was greater in specimens that were pre-implanted with helium using the tritium trick. The radioactive decay characteristics of vanadium alloys will simplify waste disposal for spent reactor components, compared to the requirements for conventional ferrous alloys.