Zircon(ZrSiO4)is the most thoroughly studied of all candidate ceramic phases for the stabilization of plutonium. Self-radiation damage from &agr;-decay of the239Pu,which releases a 5.16 MeV &agr;-particle and a 0.086 MeV235Urecoil nucleus, can significantly affect the structure and properties of zircon. Recent computer simulations using energy minimization techniques indicate that the lowest energy configuration occurs for a defect cluster composed of two near-neighborPu3+substitutions onZr4+sites and a neighboring charge-compensating oxygen vacancy. ©2000 American Institute of Physics.