BINDING FORCES OF ACTINIDES IN WASTE-DISPOSAL GLASSES - A MOSSBAUER STUDY OF GLASSIFIED NEPTUNIUM

Np-237 Mossbauer-effect studies of glassified (3 wt.%) Np, in a glass labeled as SON 68 18 17 L1C2A2Z1 is reported. This glass was designed by the CEA-Marcoule (France) and is used in France for glassification of radioactive materials, especially fission products and actinides li ke Np, Pu and Am, for waste disposal. It is shown for the first time t hat the Lamb-Mossbauer factor (f) can give insight into the binding fo rces and the motional degrees of freedom of the bound actinide in a gl ass. We conclude that in the SON glass there exist two types of glassi fied Np. Both types show strong binding of the Np in the glass matrix. However, the first type (labeled as site 1 in the Mossbauer spectra) is much stronger bound to the glass matrix.