Photoluminescence and Photoacoustic Investigations of U and Th in Nuclear Waste Glass

摘要

Photoluminescence (PL) and photoacoustic spectroscopic (PAS) studies were performed on uranium oxide and uranium oxide and thorium oxide immobilized in sodium barium borosilicate glasses. The glass composition was similar to that of the proposed Advanced Heavy Water Reactor nuclear waste glass. These investigations were aimed at understanding the oxidation state and coordination behavior of the uranium ion in the glass matrix and the effect of Th codoping on them. The PL spectrum of both the glasses showed a green emission band at 538nm without any vibronic structure along with excitation peaks at 275, 323, 348, and 412nm. These data indicated the presence of uranium as uranate (UO_6)~(6-) in the glass matrix. On codoping with Th, PL emission output as well as the lifetime was reduced. PAS utilizing nonradiative energy transfer revealed absorption peaks at 348 and 412nm, similar to those in the excitation spectrum indicating the stabilization of uranium in the hexavalent state. No absorbance peak corresponding to tetravalent U was observed. In accordance with the PL data, the PAS data revealed that the incorporation of ThO2 produces additional defect centers in the glass structure.