Identification of the non-pertechnetate species in Hanford waste tanks, Tc(I) carbonyl complexes Page: 3 of 13
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upon the energy of its absorption edge, which occurs at 7 eV lower than that of TcO . This energy is
similar to that of TcO2, which is 7 eV lower than that of TcO .7
1.5 - - - - - - - _ -
I
b
21000 21050 210)
Photon cnerg3 (cV)
Figure 1. Tc K-edge XANES spectra of the non-pertechnetate species in tanks a) SY-103, b) SY-101
reported by Blanchard and coworkers in Ref. 6.
Identification of the non-pertechnetate species has been complicated by the fact that the ligands present in
CC waste form few lower valent technetium complexes that are hydrolytically stable in strongly alkaline
solution. While Tc(IV) aminopolycarboxylate complexes are well-known and stable towards oxidation,'9
they decompose to form TcO2.2H20 in alkaline solution.10 However, a number of Tc(IV) alkoxide
complexes are stable in alkaline solution,""12 and previous studies have shown that stable Tc(IV) alkoxide
complexes can be formed by radiolysis in alkaline solution.10 However, the alkoxides examined in
previous studies are not present in sufficient quantities in CC waste to account for the amount of non-
pertechnetate species found in tanks SY-101 and SY-103. We report the results of XANES, extended X-
ray absorption fine structure (EXAFS), and 99Tc-NMR studies on lower valent technetium complexes that
are potentially present in CC waste.
Experimental procedures. Caution: 99Tc is a P-emitter (Ema = 294 keV, T2 = 2 x 105 years). All
operations were carried out in a radiochemical laboratory equipped for handling this isotope. Technetium,
as NH499TcO4, was obtained from Oak Ridge National Laboratory. The solid NH499TcO4 was
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Lukens, Wayne W.; Shuh, David K.; Schroeder, Norman C. & Ashley, Kenneth R. Identification of the non-pertechnetate species in Hanford waste tanks, Tc(I) carbonyl complexes, article, October 16, 2003; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc782186/m1/3/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.