Positron annihilation study of radiation damage in neutron-irradiated zirconium and its alloys

Abstract

Nominally pure zirconium and its alloys Zr1wt.%Nb and Zrwt.% Cu0.40wt.% Fe0.55wt.% Mo-0.20wt.% V irradiated at 60, 300 and 450°C to fast neutron fluences of 10 21, 10 22 and 10 23 m −2 (E >1 MEV) were studied by the angular correlation positron annihilation (PA) method. A pronounced dependence of PA parameters on the irradiation temperature indicates that there is a decrease in the amount of defects of an open-volume nature which are sampled by the positron at higher irradiation temperatures. At lower temperatures there is a particularly strong increase in the parabolic (free electron) annihilation component of the multicomponent alloy: this is tentatively associated with self-interstitial trapping at undersized solute atoms. High dislocation densities present in pure zirconium and the Zr1 wt.%b alloy before irradiation seem to have little effect on positron trapping at irradiation defects in these materials and on the irradiation damage processes.