X-ray absorption fine structure of aged, Pu-doped glass and ceramic waste forms

X-ray absorption spectroscopic (XAS) studies were performed on three compositionally identical, Pu-doped, borosilicate glasses prepared 15 years ago at different alpha-activities by varying the Pu-239/Pu-238 isotopic ratio. The resulting alpha-activities ranged from 1.9 x 10(7) to 4.2 x 10(9) Bq/g and have current, accumulated doses between 8.8 x 10(15) to 1.9 x 10(18) alpha-decays/g. Two ceramic, polycrystalline zircon (ZrSiO4) samples prepared 16 years ago with 10.0 wt% Pu was also investigated. Varying the Pu-239/Pu-238 isotopic ratio in these samples resulted in alpha-activities of 2.5 x 10(8) and 5.6 x 10(10) Bq/g and current, accumulated doses of 1.2 x 10(17) and 2.8 x 10(19) alpha-decays/g. The multicomponent composition of the waste forms permitted XAS investigations at six absorption edges for the borosilicate glass and at three absorption edges for the polycrystalline zircons. For both waste forms, analysis of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectra indicates that the local environment around the cations exhibits different degrees of disorder as a result of the accumulated alpha-decay dose. In general, cations with short cation-oxygen bonds show little effect from self-radiation whereas cations with long cation-oxygen bonds show a greater degree of disorder with accumulated alpha-decay dose. (C) 1998 Elsevier Science B.V.