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

Lukens, Wayne W.; Shuh, David K.; Schroeder, Norman C.; Ashley, Kenneth R.

doi:10.1021/es034318d

Cited by 72 publications

(106 citation statements)

References 26 publications

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“…The Department of Energy Hanford Site in eastern Washington State is the largest nuclear waste storage site in the United States, with 54 million gallons of radioactive waste contained underground in storage tanks [1][2][3]. The first tank leak, reported in 1956, was a result of corrosion, with about 67 tanks believed to have leaked about 0.75-1.5 million gallons of radioactive waste into the soil, resulting in the contamination of the vadose zone [4].…”

Section: Introductionmentioning

confidence: 99%

Pertechnetate immobilization with amorphous iron sulfide

Liu

Terry

Jurisson³

2008

Radiochimica Acta

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Section: Introductionmentioning

confidence: 99%

Pertechnetate immobilization with amorphous iron sulfide

Liu

Terry

Jurisson³

2008

Radiochimica Acta

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“…The chemical form of technetium in the raw tank waste is usually pertechnetate, but lower valent complexes may be present in some tanks. [12][13][14][15][16] When the waste is incorporated into glass, the nitrate and nitrite will oxidize all of the organic compounds and will oxidize technetium to Tc(VII) (fused nitrate is an extremely powerful oxidizing agent). At the maximum temperature of the glass melt, Tc(VII) can lose oxygen and drop to a lower oxidation state, which likely will have a different solubility in the glass than Tc(VII).…”

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confidence: 99%

Redox-dependent solubility of technetium in low activity waste glass

Soderquist

Schweiger

Kim

et al. 2014

Journal of Nuclear Materials

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The solubility of technetium was measured in a Hanford low activity waste glass simulant. The simulant glass was melted, quenched and pulverized to make a stock of powdered glass. A series of glass samples were prepared using the powdered glass and varying amounts of solid potassium pertechnetate. Samples were melted at 1000°C in sealed fused quartz ampoules. After cooling, the bulk glass and the salt phase above the glass (when present) were sampled for physical and chemical characterization. Technetium was found in the bulk glass up to 2000 ppm (using the glass as prepared) and 3000 ppm (using slightly reducing conditions). The chemical form of technetium obtained by x-ray absorption near edge spectroscopy can be mainly assigned to isolated Tc(IV), with a minority of Tc(VII) in some glasses and TcO 2 in two glasses. The concentration and speciation of technetium depends on glass redox and amount of technetium added. Solid crystals of pertechnetate salts were found in the salt cake layer that formed at the top of some glasses during the melt. BackgroundRadioactive waste from decades of plutonium production is currently stored in large underground tanks at the Hanford Site. This waste will be mixed with glass formers and then vitrified. 1 The Hanford tank wastes vary widely in composition, but are typically largely sodium nitrate, nitrite, and carbonate with a small amount of hydroxide.2; 3 Aluminum, iron and zirconium comprise 20% or more of the waste in some cases. Chromium and manganese may be present up to several percent. not recover all of the plutonium from the irradiated uranium, and a small amount of plutonium, uranium and americium are also found in the tanks. Many of the waste components do not incorporate well into silicate glasses. A number of ionic compounds such as sulfates have low solubility in silicate glasses and may form a separate salt phase.The current plan is to chemically separate the waste into a small volume of high-level waste, intensely radioactive from 90 Sr and 137 Cs, and a large volume of low-activity waste (LAW). 1 These two fractions will be vitrified separately. Technetium will report to the low-activity waste and will be vitrified in that fraction. Tc in LAW GlassPage 2 of 21Technetium incorporates poorly into silicate glass in traditional glass melting. Technetium readily evaporates during melting of glass feeds (waste + additives) and out of the molten glass, leading to low retention in a final glass product. [4][5][6][7] To effectively manage technetium retention in the Hanford LAW glass, it is critical to understand if the solubility of technetium is a controlling factor. The speciation of technetium in glass has been previously studied, and the technetium species present in waste glass have been previously reported; [8][9][10][11] however, the solubilities of these species are unknown.The solubility of technetium and many other waste constituents depends partly on their chemical forms.A particular constituent may be better incorporated into the glass if it is adde...

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“…Because X-ray spectroscopic techniques do not destroy the sample, spectra can be obtained for several different elements in the same sample and the sample can be subsequently used for further experiments. X-ray spectroscopic techniques have been used to determine uranium speciation in soils from the deep subsurface in the northwestern USA [45] and from Kuwait [46], to analyze mercury speciation in soils [47 ], and to determine the chemistry of technetium in wastes [48]. Oliver et al [49,50] used X-ray spectroscopy to monitor Cr(VI) reduction in soil microcosms and this method was also used to monitor the microbial reduction of technetium [51] and uranium [52] by pure cultures, as well as to study uranium in microcosm studies [42 ].…”

Section: Solid Phase Based Methods For Metal Analysismentioning

confidence: 99%