Solubility and oxidation state of uranium under anoxic conditions (N2 atmosphere)

Kaija Ollila, Markus Olin, Maija Lipponen

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

The UO2-matrix solubility is a critical parameter for predicting the stability of spent nuclear fuel under disposal conditions. This paper presents the results obtained from the dissolution experiments of unirradiated sintered polycrystalline UO2 pellets in deionized water, in NaHCO3 solutions, and in two different synthetic groundwaters under anoxic conditions (N2) at 25°C. The oxidation state of uranium in solution was determined experimentally using a method based on the separation of the tetravalent and hexavalent states by ion-exchange chromatography in HCl medium. The uranium contents of each fraction were analysed by ICP-MS. In order to study the controlling phase for the concentration of uranium at steady state in the solutions, a comparison of the experimental data was made with the solubilities calculated with the geochemical code EQ3/6. The measured concentrations were at the level of the solubilities of the mixed valence oxide, U4O9, in all solutions. The dominant oxidation state was the U(VI) state.
Original languageEnglish
Pages (from-to)9-13
Number of pages5
JournalRadiochimica Acta
Volume74
Issue numberS1
DOIs
Publication statusPublished - 1996
MoE publication typeA1 Journal article-refereed

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Uranium
uranium
solubility
Solubility
atmospheres
Oxidation
oxidation
spent fuels
inductively coupled plasma mass spectrometry
Deionized water
nuclear fuels
Spent fuels
disposal
Nuclear fuels
chromatography
ground water
Chromatography
pellets
Oxides
Groundwater

Cite this

Ollila, Kaija ; Olin, Markus ; Lipponen, Maija. / Solubility and oxidation state of uranium under anoxic conditions (N2 atmosphere). In: Radiochimica Acta. 1996 ; Vol. 74, No. S1. pp. 9-13.
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Solubility and oxidation state of uranium under anoxic conditions (N2 atmosphere). / Ollila, Kaija; Olin, Markus; Lipponen, Maija.

In: Radiochimica Acta, Vol. 74, No. S1, 1996, p. 9-13.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Solubility and oxidation state of uranium under anoxic conditions (N2 atmosphere)

AU - Ollila, Kaija

AU - Olin, Markus

AU - Lipponen, Maija

PY - 1996

Y1 - 1996

N2 - The UO2-matrix solubility is a critical parameter for predicting the stability of spent nuclear fuel under disposal conditions. This paper presents the results obtained from the dissolution experiments of unirradiated sintered polycrystalline UO2 pellets in deionized water, in NaHCO3 solutions, and in two different synthetic groundwaters under anoxic conditions (N2) at 25°C. The oxidation state of uranium in solution was determined experimentally using a method based on the separation of the tetravalent and hexavalent states by ion-exchange chromatography in HCl medium. The uranium contents of each fraction were analysed by ICP-MS. In order to study the controlling phase for the concentration of uranium at steady state in the solutions, a comparison of the experimental data was made with the solubilities calculated with the geochemical code EQ3/6. The measured concentrations were at the level of the solubilities of the mixed valence oxide, U4O9, in all solutions. The dominant oxidation state was the U(VI) state.

AB - The UO2-matrix solubility is a critical parameter for predicting the stability of spent nuclear fuel under disposal conditions. This paper presents the results obtained from the dissolution experiments of unirradiated sintered polycrystalline UO2 pellets in deionized water, in NaHCO3 solutions, and in two different synthetic groundwaters under anoxic conditions (N2) at 25°C. The oxidation state of uranium in solution was determined experimentally using a method based on the separation of the tetravalent and hexavalent states by ion-exchange chromatography in HCl medium. The uranium contents of each fraction were analysed by ICP-MS. In order to study the controlling phase for the concentration of uranium at steady state in the solutions, a comparison of the experimental data was made with the solubilities calculated with the geochemical code EQ3/6. The measured concentrations were at the level of the solubilities of the mixed valence oxide, U4O9, in all solutions. The dominant oxidation state was the U(VI) state.

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