Impurity Hot Atoms in Irradiated Metals with Different Nuclear History

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Abstract

General relationships in the effect of the nuclear history on the forms of stabilization of impurity hot atoms and on the diffusion mobility and specific features of the physicochemical behavior of radioactive micro-impurities in the course of annealing of radiation-induced perturbations and of structural transformations of irradiated metals were elucidated. The forms of stabilization of impurity hot atoms in metals after irradiation and in the course of annealing of radiation-induced perturbations and of structural transformations, were determined by emission Mössbauer spectroscopy. It was shown that the positions occupied by impurity atoms in irradiated metals are determined by the nuclear history and crystallographic features of these metals. Studies of how impurity hot atoms formed by nuclear transformations migrate in the course of annealing of the irradiated metals show that the rate of migration of radioactive micro-impurities is determined by the extent of the radiation damage of the targets and by the possible position of the impurity hot or daughter atom in the crystal lattice of the irradiated metal. The transport mechanism accounting for the anomalous behavior of impurities is suggested. Anomalies (accelerated diffusion in the bulk and in surface layers of irradiated metals and emanation into the gas phase) in the physicochemical behavior of impurity atoms in the course of structural transformations of irradiated metals were revealed. These anomalies depend on the nuclear and mechanical history of the samples and on the conditions of their annealing. The interrelation between the nuclear history, crystallographic position of impurity hot atoms, their physicochemical characteristics, and structural changes occurring in metals in the course of irradiation, annealing of radiation-induced perturbations, and structural transformations was demonstrated by X-ray phase analysis and various kinds of Mössbauer spectroscopy. For metals having several allotropic modifications (Mn, Fe, Sn), the effect of stabilization of high- and low-temperature structural phases at room temperature upon irradiation was discovered.

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