Dissolution of TcO<sub>2</sub> in Aqueous Solutions under Various Conditions

Lieser, Κ. H.; Bauscher, Ch.; Nakashima, Tsunehiko

doi:10.1524/ract.1987.42.4.191

Cited by 22 publications

(16 citation statements)

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“…Similarly, the differences in electrode potential observed by different investigators [15] may also be the results of differences in structure and composition. Anhydrous technetium oxide, Tc0 2 , can be prepared by high temperature preparative techniques; however, attempts to measure the electrode potential [16] and Tc(IV) solubility [17] of this material have not been successful. Apparently it is a much less soluble form of Tc(IV) oxide, and the only observed dissolution was the formation of Tc(VII), which depended upon the amount of dissolved oxygen [17].…”

Section: Discussionmentioning

confidence: 99%

Solubilities of Tc(IV) Oxides

et al. 1991

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Solubilities of Tc(IV) oxides have been determined in a number of solutions in the pH range 1 to 10. Technetium oxide was prepared by precipitation upon purified sand with a 30% excess of hydrazine and by electrodeposition. The oxide-covered sand was transferred to a small column, and the solutions to be studied were continuously cycled through the column. The electrodeposited oxide was formed on a platinum mesh electrode, and after careful rinsing, the solution to be studied was added to the electrolytic cell. The concentrations of total technetium and Tc(IV) species in the solutions were periodically determined by separating the oxidized and reduced technetium species using a solvent extraction procedure and counting the beta activity of the "Tc with a liquid scintillation counter. In basic solutions, the concentrations of Tc(IV) species in equilibrium with the oxide were in the range of 10" 8 to 10 ~ 9 mol/1 and tended to increase slightly with pH. In acid solutions the concentrations were much higher and were consistent with literature data on the hydrolytic species of Tc(IV). Solubilities appeared to reach a minimum in the intermediate pH range, and they were generally a factor of three or four lower for oxides electrodeposited in basic solutions compared to those for oxides electrodeposited from acid solution. The oxides were hydrated, and assuming a formula of Tc0 2 · nH 2 0, the value of η was found to be 1.63 ± 0.28. These data can be used to estimate Tc(IV) solubilities for cases where solubility limits transport of technetium in reducing environments of high-level waste repositories.

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Section: Discussionmentioning

confidence: 99%

Solubilities of Tc(IV) Oxides

et al. 1991

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“…In presence of water, however, the following scenario has to be considered: corrosionleaching (dissolution) -transport (migration). TCO4 is dissolved quickly, whereas TCO2 shows diflferent behaviour under aerobic and anaerobic conditions [15], as shown in Fig. 3.…”

Section: Technetium In the Environmentmentioning

confidence: 91%

Technetium in the Nuclear Fuel Cycle, in Medicine and in the Environment

Lieser

1993

Radiochimica Acta

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110

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Technetium / Nuclear fuel cycle / Medicine / Environment / Radionuclide generator / Radionuclide purity SummaryFormation of ''To in nuclear reactors and the fate of Tc in reprocessing plants are described. "Mo/'''"Tc radionuclide generators for use in nuclear medicine, the production of the importance of nuclear purity control and the selection of suitable Compounds of Tc are discussed. The ways by which Tc may enter the environment, the dissolution of TCO2 and the different migration and Sorption behaviour of Tc(IV) and Tc(Vll) are explained and the importance of the interaction of Tc with organic Compounds is emphasized.

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“…The behavior of Tc(IV) species is very different from Tc(VII), and Tc(IV) may become complexed and strongly sorbed onto mineral surfaces [245]. The solubility limiting phase is expected to be TcO2 under most conditions [246]. …”

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The effects of the glass surface area/solution volume ratio on glass corrosion: A critical review

Ebert

1995

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Argonne National Lahoratory. wi1th facilitie, in the states of liiinois and Idaho. is owned by the united States govern lent, and operated by The Un diversity of Chicago under the provisions of a contract with thie department of Enery. DISCLAIM ER THE FFFECTS OF THE GLASS SURFACE AREA/SOLUTION VOLUME RATIO ON GLASS CORROSION: A CRITICAL REVIEW William L. Ebert ABSTRACTThis report reviews and summarizes the present state of knowledge regarding the effects of the glass surface area/solution volume (SA/V) ratio on the corrosion behavior of borosilicate waste glasses. The SA/V ratio affects the rate of glass corrosion through the extent of dilution ok corrosion products released from the glass into the leachate solution: glass corrosion products are diluted more in tests conducted at low SA/V ratios than they are in tests conducted at high SAN ratios. Differences in the solution chemistries generated in tests conducted at different SA/V ratios then affect the observed glass corrosion behavior. Corrosion of borosilicate waste glasses results in the dissolution of soluble components and the accumulation of sparingly soluble components in a layer on the surface of the corroding glass. Laboratory tests performed to distinguish the effects of the solution chemistry and the surface layer on the glass corrosion rate have shown the rate to be controlled primarily by the solution chemistry. Therefore, any testing parameter that affects the solution chemistry will also affect the glass corrosion rate. The results of static leach tests conducted to assess the effects of the SAN are discussed with regard to the effects of SAN on the solution chemistry. The effects of the SA/V ratio observed in static tests can be understood based on the effects of the solution chemistry on glass corrosion behavior. Test results show several remaining issues with regard to the long-term glass corrosion behavior: Can the SAN ratio be used as an accelerating parameter to characterize the advanced stages of glass corrosion relevant to long disposal times? Is the alteration of the glass surface the same in tests conducted at different SAN, and in tests conducted with monolithic and crushed glass samples? What are the effects of the SAN and the extent of glass corrosion on the disposition of released radionuclides? These issues will bear on the prediction of the long-term performance of waste glasses during storage. The results of an experimental program conducted at ANL to address these and other remaining issues regarding the effects of SA/V on glass corrosion are described. I 2 SUMMARYThis report reviews and summarizes the present state of knowledge regarding the effects of the glass surface area/solution volume ratio (SA/V) on the corrosion behavior of borosilicate waste glasses. The effects of the SA/ occur through dilution of corrosion products and through the effects of the corrosion products on the glass corrosion mechanism and rate. Therefore, the effects of the SA/V on glass corrosion are discussed in terms of the various effects of t...

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Dissolution of TcO₂ in Aqueous Solutions under Various Conditions

Cited by 22 publications

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Solubilities of Tc(IV) Oxides

Solubilities of Tc(IV) Oxides

Technetium in the Nuclear Fuel Cycle, in Medicine and in the Environment

The effects of the glass surface area/solution volume ratio on glass corrosion: A critical review

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Dissolution of TcO2 in Aqueous Solutions under Various Conditions

Cited by 22 publications

References 0 publications

Solubilities of Tc(IV) Oxides

Solubilities of Tc(IV) Oxides

Technetium in the Nuclear Fuel Cycle, in Medicine and in the Environment

The effects of the glass surface area/solution volume ratio on glass corrosion: A critical review

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Dissolution of TcO₂ in Aqueous Solutions under Various Conditions