| AVS 66th International Symposium & Exhibition | |
| Actinides and Rare Earths Focus Topic | Tuesday Sessions |
| Session AC+AS+LS-TuM |
| Session: | Chemistry and Physics of the Actinides and Rare Earths |
| Presenter: | David Shuh, Lawrence Berkeley National Laboratory |
| Authors: | D.K. Shuh, Lawrence Berkeley National Laboratory D. Caulder, Lawrence Berkeley National Laboratory L. Davis, Pacific Northwest National Laboratory M. Mara, University of California at Berkeley C.H. Booth, Lawrence Berkeley National Laboratory J. Darab, Pacific Northwest National Laboratory J. Icenhower, Pacific Northwest National Laboratory D. Strachan, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
One method for the safe disposal of actinides currently under consideration by the U.S. Department of Energy is immobilization of radionuclides in a glass or ceramic wasteform that will subsequently be stored in a geological repository. To develop successful, stable wasteforms, it is necessary to acquire an understanding of the fundamental chemistry of the actinides (U, Pu, etc.) and neutron absorbers (B, Gd, Hf) that will be incorporated into the glass or ceramic matrix. The X-ray absorption near edge structure (XANES) at the hafnium L3 and L1 absorption edges has been investigated to elucidate the local structure of Hf in wasteform glasses that are currently being considered as candidates for the immobilization of radionuclides. During our investigations of the structure of Hf, a neutron absorber and potential Pu(IV) surrogate, we noted an unusual feature at the white line maximum at the L3 absorption edge: The examination of a variety of Hf model compounds demonstrates that the second derivative of the Hf L3 XANES displays structure characteristic of crystal field splitting of the empty d-manifold. The peralkaline glasses studied exhibit L3 XANES spectra typical of Hf in an octahedral crystal field. The L1 XANES data corroborate these results, as the L1 spectra of the glasses also resemble that of an octahedral Hf siloxane model compound, distinct from spectra of other standards measured.