Review of the behavior of helium bubbles in aged plutonium and their influence on material properties

The latest understanding of helium (He) bubbles in aged plutonium (Pu) and their effects on the properties and behavior of Pu is reviewed and compared to results from our laboratory. The radioactive decay of Pu atoms leads to the generation of uranium (U) atoms and alpha particles, the latter resulting in the evolution of He atoms, which aggregate over time to form He bubbles in the Pu lattice. A variety of techniques have been used to understand the He diffusion in aged Pu and the mechanisms of bubble formation. Also discussed are the effects of He bubbles on the mechanical properties (e.g., strength and hardness) as a result of the continuing formation of He bubbles over time.