Modeling cascade and fission damage evolution of actinide materials of all kinds is essential for understanding their aging characteristics. As an example of how exotic some of the damage evolution behavior can be, plutonium-gallium (Pu-Ga) alloys in the δ-phase (fcc lattices) are explored. Aging emanates from the wide variety of spontaneous decay and fission products that, in the case of the Pu, are such species as helium (He) and uranium, among others, as well as interstitials, and vacancies. To aid in our understanding, the modified embedded atom method (MEAM) formalism is applied to the Pu-Ga-He system. The behavior of defects in the fcc (δ) phase of Pu-based materials is strongly influenced by the metastability of this phase. The influence of this metastability on minimum displacement threshold energy, point defect characteristics and He bubbles is delineated. The roles of short-range ordering and transformations of voids into stacking fault tetrahedra in the aging process are also examined.