Study by XRD of the lattice swelling of PuGa alloys induced by self-irradiation

Plutonium aging leads to the creation of decay products, such as americium, uranium and helium and self-irradiation defects such as vacancies, vacancy clusters, self-interstitials and helium bubbles. As these self-irradiation defects accumulate in plutonium–gallium alloys, the lattice parameters of the material change. Thus, this work is an X-ray diffraction (XRD) study of the lattice parameter changes, such as kinetics and amplitude, as a function of self-irradiation dose for non-homogenized and homogenized samples. The results have shown no incubation time before the beginning of lattice swelling. Moreover, whereas the lattice swelling amplitude seems to be influenced by the gallium segregation to the border of grain in non-homogenized samples, it is not strongly influenced by the gallium concentration. An average lattice parameter increase of about 4.5 × 10−3 Å is observed for homogenized alloys at saturation. This equilibrium is achieved after a dose of 0.1 dpa. A discussion of possible causes leading to these observations and their effects is presented.