The influence of nuclear transmutations on phase stability of v-alloys and low activation ferritic steel under neutron irradiation

Full text of publication follows: There are many processes takes place in materials under neutrons irradiation including the transformation of chemical elements due to nuclear transmutations. Burning up and formation of the main elements of alloys may stimulate essential phase modifications, which may control the properties of metallic materials changing at high temperatures. To study this problem the computations of the chemical composition changes while neutrons irradiation of low activation ferritic steel (Fe9Cr2WVMn) and vanadium-based alloys (V-4Ga, V-3,6Ga-0,82Si and V-4Cr-4Ti) have been carried out as well as the activation of these materials has been estimated. The following data have been used for computations : neutron spectrum DEMO, fluence - 2.1027 n/m2, duration of irradiation - 10 years, the results of panoramic element analysis of the samples (ICP MS data). The analysis of the results obtained shows that duration of cooling of V-alloys to reach dose which fits to hand-on limit is about 25 years, whereas the correspondent period for low activation ferritic steel is slightly less than 100 years. The burning up and formation of chemical elements in the irradiated ferritic steel is insignificant. In V4GaSi alloy gallium has the highest burning up percentage (∼3%). For V4Cr4Ti alloy one can state that titanium is burning up noticeably (∼7,5%) and chromium concentration is incrementing (∼2,4%). But according to phase diagrams the results of transmutations do not result in changes of phase composition, in the contrast to steels under thermal neutrons irradiation [1]. A special study has been paid to formation of gas forming elements (H, He, N, C) in the vanadium-based alloys. References 1. Alenina et al. Journal of Advance Materials, 2000(3), p.54. (authors)