Phasengleichgewichte in den systemen uranoxid-oxide der seltenen erden (Ho, Er, Tm, Yb, Lu)

Keller, C.; Engerer, H.; Leitner, L.; Sriyotha, U.

doi:10.1016/0022-1902(69)80144-2

Cited by 29 publications

(5 citation statements)

References 14 publications

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“…The formation enthalpy of U 1-z Ln z O 2 compounds ( Ln = La, Nd, Y) becomes strongly more negative with the Ln fraction, z , for 0 < z < 0.5. The stability of these compounds correlates with an independent observation that Ln -doped solid solutions of intermediate compositions (0.5 < z < 0.67) synthesized in strongly oxidizing conditions at temperatures of about 1273 K after achieving the stoichiometric relationship of O/M ~ 2 do not oxidize further to hyper-stoichiometry 25 – 30 . Based on the measured endothermic energies Mazeina et al 23 suggested that the activity of the UO 2 endmember is greatly reduced in doped fluorite solid solutions making them less prone to oxidation.…”

Section: Introductionsupporting

confidence: 72%

“…The and parameters of the endmember were estimated with the additivity rule. The parameter of the endmember endmember and the Margules parameter for the interaction between and species were adjusted such that at T > 1173 K in air the model predicted a strong partitioning of Ln O 1.5 into the fluorite phase, consistently with the high-temperature equilibrium data 25 – 30 , while at T < 973 K the same model predicted the destabilization of fluorite relative to a Ln -rich M 3 O 8 phase, consistently with the air oxidation experiments of Potts et al 50 .…”

Section: Methodsmentioning

confidence: 62%

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Thermodynamic model of the oxidation of Ln-doped UO2

Vinograd,

Bukaemskiy,

Deissmann

et al. 2023

Sci Rep

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Ln-doped UO2 is often considered as a model system of spent nuclear fuel (SNF) helping to reveal effects of fission and activation products on its chemical stability. Comparing thermodynamics of UO2-UO3 and LnO1.5-UO2-UO3 systems provides a means to understand the phenomenon of an increased resistivity of Ln-doped UO2 to oxidation in air relative to pure UO2. Here a thermodynamic model is developed and is applied to investigate detailed phase changes occurring along the oxidation of Ln-doped fluorite to U3O8. The study proposes that an enhanced resistivity to oxidation of Ln-doped UO2 is likely caused by a thermodynamically driven partitioning of Ln between a fluorite-type phase and a U3O8 polymorph, which at ambient temperatures becomes hindered by slow diffusion.

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Section: Introductionsupporting

confidence: 72%

Section: Methodsmentioning

confidence: 62%

Thermodynamic model of the oxidation of Ln-doped UO2

Vinograd,

Bukaemskiy,

Deissmann

et al. 2023

Sci Rep

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“…Oxygen potentials that give the stoichiometry at each temperature were defined as those showing steep increases with increase of O/M ratio. This definition is appropriate considering the similarity between the Lu-U-O system and other RE-U-O systems [16] which show the steep increase of DG O 2 at the stoichiometry. Fig.…”

Section: Methodsmentioning

confidence: 99%

Oxygen potential of hypo-stoichiometric Lu-doped UO2

Osaka

Tanaka

2008

Journal of Nuclear Materials

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a b s t r a c tOxygen potentials of hypo-stoichiometric Lu-doped UO 2 , (U 0.80 Lu 0.20 )O 2Àx , were experimentally investigated by thermogravimetric analysis using H 2 O/H 2 gas equilibria at 1173, 1273 and 1473 K. The oxygen potentials of (U,Lu)O 2Àx were higher than those of other forms of rare earth-doped UO 2 , specifically (U,Nd)O 2Àx , (U,Gd)O 2Àx , and (U,Er)O 2Àx . Slope analyses for plots of oxygen potential versus deviation from stoichiometry indicated that (U 0.80 Lu 0.20 )O 2Àx had a similar defect structure to that of the other forms of rare earth-doped UO 2 . A relationship between the effective ionic radii and oxygen potentials was found for the hypo-stoichiometric rare earth-doped UO 2 .

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“…Oxygen non-stoichiometric (U,Ln)O 2±x (Ln: Lanthanide elements) are of particular importance from the viewpoint of evaluation of irradiation behavior of UO 2 -based nuclear fuels. Lanthanides have generally high fission yields and form solid solutions with UO 2 over a wide range of Ln contents [1]. This fact requires a systematic database of thermochemial and thermophysical properties for the (U,Ln)O 2±x in order to evaluate the irradiation behavior.…”

Section: Introductionmentioning

confidence: 99%

“…The stoichiometry, O/M=2.00, at each temperature was defined as that showing the steep increase of oxygen partial pressure with an increase of the O/M ratio. This definition is appropriate considering the similarity between the La-U-O system and other RE-U-O (RE: Rare-earth) systems[1] which show the steep increase of around the stoichiometry. Estimated errors of the oxygen potential, which is defined by using Eq.…”

mentioning

confidence: 99%

Oxygen potential of hypo-stoichiometric La-doped UO2

Yoshida

Arima

Inagaki

et al. 2011

Journal of Nuclear Materials

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Oxygen potential of hypo-stoichiometric (U 0.8 La 0.2)O 2-x was measured as a function of oxygen-to-metal ratio (2-x) at the temperature range from 1173 K to 1473 K. Comparing with uranium oxides doped with other lanthanides, e.g. Lu, Er, Gd and Nd, the relationship between 2 O ΔG and the oxygen-to-metal ratio obtained for this sample showed almost the same trend, and for the relatively large oxygen non-stoichiometry x, its significance was comparable with that of

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Phasengleichgewichte in den systemen uranoxid-oxide der seltenen erden (Ho, Er, Tm, Yb, Lu)

Cited by 29 publications

References 14 publications

Thermodynamic model of the oxidation of Ln-doped UO2

Thermodynamic model of the oxidation of Ln-doped UO2

Oxygen potential of hypo-stoichiometric Lu-doped UO2

Oxygen potential of hypo-stoichiometric La-doped UO2

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