Neutron diffraction study of delta -alloy Pu super(242)-Ga aging

In this paper, we report on a continuing neutron, diffraction study of the mean-square atom displacements occurring during the long-term self-irradiation of a Pu-Ga alloy. The measurements were performed at room temperature using the sample based on the isotope Pu super(242) with low neutron absorption cross-section to which the short-lived isotope Pu super(238) (1.4 wt.%) was added to accelerate self-irradiation. We obtain the maximum self-irradiation equivalent time of 35.5 years, 12 years longer than in our previous papers. In the entire range of self-irradiation time a single fee phase is preserved. It was found that after the two stages of change in the mean-square displacements we observed earlier (rapid growth up to ~5-6 equivalent years and a slow decline in the range of ~6-25 years), comes a stage of stabilization (after ~25 years). The stabilization can be explained by the emergence of a balance between the formation of point defects and their absorption by helium bubbles and dislocation loops which accumulated over time.