Identification of the non-pertechnetate species in Hanford waste tanks, Tc(I)--carbonyl complexes.

Immobilization of the high-level nuclear waste stored at the Hanford Reservation has been complicated by the presence of soluble, lower-valent technetium species. Previous work by Schroeder and Blanchard has shown that these species cannot be removed by ion-exchange and are difficult to oxidize. The Tc K-edge XANES spectra of the species in Tanks SY-101 and SY-103 were reported by Blanchard, but they could not be assigned to any known technetium complex. We report that the XANES spectra are most likely those of Tc(I)-carbonyl species, especially fac-Tc(CO)3(gluconate)(2-). This is further supported by EXAFS and 99Tc-NMR studies in nonradioactive simulants of these tank wastes.