Reaction of uranium(IV) chloride with oxygen in alkali chloride melts: An electronic absorption spectroscopy study

Kozlova, A. A.; Рыжов, А. А.; Ivanov, Alexander B.; Maltsev, Dmitry S.; Shchetinskiy, A. V.; Новоселова, А. В.; Volkovich, Vladimir A.

doi:10.1063/1.5134185

Cited by 2 publications

(6 citation statements)

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“…Comparison of the results obtained here in LiCl melts with previous findings in LiCl-KCl eutectic 13 showed that under identical conditions (temperature, gas phase composition, O 2 : UCl 4 molar ratio) the amount of uranium precipitated from the melt was always considerably higher in LiCl based systems. Therefore, taking into account that no uranium precipitation was observed in cesium containing chloride melts (NaCl-KCl-CsCl and NaCl-CsCl eutectics) 13,14 it indeed appears that decreasing alkali cation radius (increasing polarizing ability of the cation) has a noticeable effect on the products of the reaction of oxygen with dissolved uranium tetrachloride. A possible reason for this might be increasing stability of uranyl chloro-ions in the melts with larger cations.…”

Section: Resultssupporting

confidence: 77%

“…Only in LiCl-KCl based melts a fraction of uranium was precipitated as an oxide. 13,14 In the melts with larger cations (NaCl-KCl-CsCl and NaCl-CsCl mixtures) bubbling oxygen through the melts did not result in decreasing uranium concentration. Lithium chloride offers the system with the smallest cations and it was selected to check whether the solvent salt indeed had the effect on the reaction products formed.…”

Section: Resultsmentioning

confidence: 96%

“…The amount of oxygen passed through the melt was varied to set different O 2 : UCl 4 molar ratios (from 5 to 50), similar to the previous studies in LiCl-KCl-UCl 4 melts. 13 Thermodynamic calculations (using HSC 6.1 software) indicated that uranium oxides (UO 3 and U 3 O 8 ) and oxychlorides were expected, Fig. 3.…”

Section: Resultsmentioning

confidence: 99%

“…Previous bulk studies of O 2 bubbling through LiCl-KCl-UCl 4 melts at 550 and 750 °C showed, however, that only a small fraction of uranium was precipitated. 13 Most uranium remained in the soluble form.…”

Section: Resultsmentioning

confidence: 99%

“…12 Treating solutions of uranium tetrachloride in fused alkali chlorides with oxygen or argon-oxygen mixtures resulted in partial precipitation of uranium as UO 2 ; most uranium was oxidized to uranyl species and remained in the soluble state in the melt. 13,14 Continuous oxygen bubbling through LiCl-KCl-UCl 4 melts resulted in less than 20% precipitation of uranium as uranium oxide, U 3 O 8 . 14 Using moist oxygen lowered and sometimes completely prevented formation of insoluble uranium compounds in LiCl-KCl eutectic based melts.…”

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confidence: 99%

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Reaction of Oxygen with Uranium (IV) Chloride in Fused Alkali Chlorides

Volkovich

Рыжов

2023

J. Electrochem. Soc.

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Reaction of oxygen with solutions of uranium(IV) chloride in fused LiCl and three alkali chloride eutectic mixtures (LiCl–KCl, NaCl–KCl–CsCl, and NaCl–CsCl) was investigated at 550–750°C. Bubbling oxygen or oxygen-containing gas mixtures (O2–H2O, O2–Ar, O2–H2O–Ar) through LiCl–UCl4 melts resulted in significant precipitation of uranium (up to 87%) in the form of oxides and alkali uranates. Increasing mean radius of the solvent melt cations decreased the degree of uranium precipitation and uranyl chloride (soluble in the melt) became the main product of the reaction. High-temperature spectroscopy measurements were employed to determine the kinetic parameters of the reaction in LiCl–KCl, NaCl–KCl–CsCl, and NaCl–CsCl melts. Reaction rates, order, rate constants, and activation energy values were estimated. Increasing temperature led to increased reaction rates but the effect of uranium chloride concentration depended on the cationic melt composition. Oxygen reacts with uranium(IV) containing melts much faster than with the melts containing rare earth chlorides and oxygen sparging can be implemented for separating uranium and rare earth fission products in pyrochemical reprocessing of spent nuclear fuels.

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Section: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Reaction of Oxygen with Uranium (IV) Chloride in Fused Alkali Chlorides

Volkovich

Рыжов

2023

J. Electrochem. Soc.

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Kinetics of Reaction of Oxygen with Uranium(IV) Chloride in Alkali Chloride Melts

et al. 2020

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Reaction of oxygen with solutions of uranium tetrachloride in molten alkali chlorides was studied. The experiments were performed in LiCl–KCl, NaCl–KCl–CsCl, and NaCl–CsCl eutectic based melts at 450–750oC. Pure oxygen and argon–oxygen mixtures (containing ca. 1 and 10% O2) were used. Amount of oxygen passed through the melt varied from less than one to over 100 moles per mole of uranium present. In addition the reaction of oxygen with the melts containing a mixture of uranium(IV) and neodymium chlorides was investigated. The course of the reactions was followed by in situ electronic absorption spectroscopy measurements with the spectra recorded at the certain time intervals. Depending on temperature, cationic melt composition, and oxygen-to-uranium molar ratio, the reaction resulted in oxidation of uranium(IV) to soluble uranyl chloride and/or precipitation of uranium oxide. Analysis of the spectra provided the information on kinetics of U(IV) concentration change and the reaction rates were determined. Increasing temperature, O2 : U(IV) molar ratio or decreasing mean radius of alkali cations of the solvent melt resulted in faster decrease of U(IV) concentration in the melt.

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Reaction of uranium(IV) chloride with oxygen in alkali chloride melts: An electronic absorption spectroscopy study

Cited by 2 publications

References 6 publications

Reaction of Oxygen with Uranium (IV) Chloride in Fused Alkali Chlorides

Reaction of Oxygen with Uranium (IV) Chloride in Fused Alkali Chlorides

Kinetics of Reaction of Oxygen with Uranium(IV) Chloride in Alkali Chloride Melts

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