Technetium Oxidation State Adjustment for Hanford Waste Processing

Schroeder, Norman C.; Radzinski, Susan D.; Ashley, Kenneth R.; Truong, Anh P.; Szczepaniak, Patrycja A.

doi:10.1007/978-1-4899-1543-6_23

Cited by 13 publications

(40 citation statements)

References 11 publications

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“…While ion exchange is effective for many tanks, it fails for Complexant Concentrate (CC) waste tanks, including tanks SY-101 and SY-103, which contain the organic complexants nitrilotriacetate (NTA), ethylenediaminetetraacetate (EDTA), citrate, and gluconate. 4,5 In these tanks, the majority of technetium is present as a soluble, lower-valent, non-pertechnetate species that is not removed during pertechnetate ion exchange. 4 The identity of this species is unknown, but its behavior is intriguing and has hampered efforts to remove it.…”

Section: Manuscript Textmentioning

confidence: 99%

“…4,5 In these tanks, the majority of technetium is present as a soluble, lower-valent, non-pertechnetate species that is not removed during pertechnetate ion exchange. 4 The identity of this species is unknown, but its behavior is intriguing and has hampered efforts to remove it. It is not readily removed by ion exchange, and although the non-pertechnetate species is air-sensitive (it slowly decomposes to pertechnetate), it is difficult to oxidize in practice.…”

Section: Manuscript Textmentioning

confidence: 99%

“…All operations were carried out in a radiochemical laboratory equipped for handling this isotope. Technetium, as NH 4 9 9 TcO 4 , was obtained from Oak Ridge National Laboratory. The solid NH 4 9 9 TcO 4 was contaminated with a large amount of dark, insoluble material.…”

Section: Manuscript Textmentioning

confidence: 99%

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Identification of the Non-Pertechnetate Species in Hanford Waste Tanks, Tc(I)−Carbonyl Complexes

Lukens

Shuh

Schroeder

et al. 2003

Environ. Sci. Technol.

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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 9 9 Tc-NMR studies in nonradioactive simulants of these tank wastes.2 KEYWORDS Technetium, Hanford, high level waste, nuclear waste BRIEFS The soluble technetium species that have caused problems for the remediation of high level nuclear waste at Hanford are most likely Tc(I) carbonyl complexes.

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Section: Manuscript Textmentioning

confidence: 99%

Section: Manuscript Textmentioning

confidence: 99%

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Identification of the Non-Pertechnetate Species in Hanford Waste Tanks, Tc(I)−Carbonyl Complexes

Lukens

Shuh

Schroeder

et al. 2003

Environ. Sci. Technol.

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“…They find that oxidation of the reduced technetium species generally requires the oxidation of the nitrate and organic material present in the waste presumably due to the slow kinetics of oxidizing the reduced technetium species. However, based upon reports by Blanchard and Schroeder (Blanchard 1995, Schroeder 1998, the reduced technetium species in the CC waste are also air sensitive although they are oxidized slowly at ambient temperature. These species could conceivably be oxidized at a greater rate by aerating them at elevated temperatures in a manner analogous to that used to oxidize Cr(III) to CrO 4 2- (Rapko 1998).…”

Section: Relevance To Em Issuesmentioning

confidence: 97%

“…The oxidation of reduced technetium species has been addressed by Schroeder and coworkers for actual waste from tank AN-107 (Schroeder 1998). They find that oxidation of the reduced technetium species generally requires the oxidation of the nitrate and organic material present in the waste presumably due to the slow kinetics of oxidizing the reduced technetium species.…”

Section: Relevance To Em Issuesmentioning

confidence: 99%

Final Report, Research Program to Investigate the Fundamental Chemistry of Technetium

Lukens¹,

Fickes²,

Bucher³

et al. 2000

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The autoreduction of pertechnetate in aqueous, alkaline solutions

Berning

Schroeder

Chamberlin

2005

J Radioanal Nucl Chem

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The autoreduction of pertechnetate (99 TcO 4-) to Tc(IV/V) alkoxide complexes in aqueous, alkaline, solutions is described. Solutions of sodium pertechnetate (0.01M) reacted with nitrogen and oxygen donor ligands (1.0M) in 2M sodium hydroxide. Solutions containing nitrogen donor ligands (e.g., EDTA) showed the initial formation of lightly colored complexes followed by rapid decomposition in air. In contrast, stable, reduced complexes were formed within minutes of mixing pertechnetate with mono-and disaccharides in strong base, as indicated by a persistent color change. Chemical yields of these reactions were determined by thin layer chromatography or paper chromatography and radiochemically assayed with a Bioscan imaging scanner. Analysis by UV-vis spectroscopy suggested that Tc(IV) or Tc(V) complexes were produced, with the oxidation state dependent on the reducing ligand. These experiments may help explain the reduction of pertechnetate to the soluble complexes that have been found in the Hanford nuclear waste tanks.

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Technetium Oxidation State Adjustment for Hanford Waste Processing

Cited by 13 publications

References 11 publications

Identification of the Non-Pertechnetate Species in Hanford Waste Tanks, Tc(I)−Carbonyl Complexes

Identification of the Non-Pertechnetate Species in Hanford Waste Tanks, Tc(I)−Carbonyl Complexes

Final Report, Research Program to Investigate the Fundamental Chemistry of Technetium

The autoreduction of pertechnetate in aqueous, alkaline solutions

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