Oxygen potential, electrical conductivity and defect structure of titanium-doped uranium dioxide

Tsuji, Takeshi; Matsui, Tsuneo; Abe, Masahiro; Naito, Kunihiko

doi:10.1016/0022-3115(89)90576-x

Cited by 22 publications

(8 citation statements)

References 18 publications

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“…This thermal gradient serves as a conduit for the diffusion of the oxygen through the sample such that the cooler part of the sample acts as a reservoir for the oxygen. UO 2 has been shown to exhibit modest conductivity at modest temperatures . Once the temperature reaches a critical value, thermodynamics drives the transformation to the orthorhombic β-SrUO 4 form, however this is only possible if there is a source of oxygen available.…”

Section: Resultsmentioning

confidence: 99%

Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral–Orthorhombic Transition in SrUO₄

et al. 2016

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In situ neutron and synchrotron X-ray diffraction studies demonstrate that SrUO4 acts as an oxygen transfer agent, forming oxygen vacancies under both oxidizing and reducing conditions. Two polymorphs of SrUO4 are stable at room temperature, and the transformation between these is observed to be associated with thermally regulated diffusion of oxygen ions, with partial reduction of the U(6+) playing a role in both the formation of oxygen deficient α-SrUO4-δ and its subsequent transformation to stoichiometric β-SrUO4. This is supported by ab initio calculations using density functional theory calculations. The oxygen vacancies play a critical role in the first order transition that SrUO4 undergoes near 830 °C. The changes in the oxidation states and U geometry associated with the structural phase transition have been characterized using X-ray absorption spectroscopy, synchrotron X-ray diffraction, and neutron diffraction.

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Section: Resultsmentioning

confidence: 99%

Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral–Orthorhombic Transition in SrUO₄

et al. 2016

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“…A (eV) (Å) C (eVÅ 6 both UO 2 and ZrO 2 . The details of the potential parameters have been discussed elsewhere [20,42].…”

Section: Speciesmentioning

confidence: 99%

“…To improve the physical, chemical and thermodynamic properties of fuel matrix and reduce fission gas release during irradiation of the fuel, lots of dopants such as oxides of niobium [1][2][3], magnesium [4,5], titanium [6][7][8] chromium [9][10][11][12], and zirconium [13][14][15][16][17][18] have been investigated in the past few decades. The solid solutions of Zr-doped UO 2 have been identified as a high performance nuclear fuel due to its desirable properties which include [13,14]: (1) the swelling rate of Zr-doped UO 2 fuel is lower than the undoped UO 2 fuel under irradiation, (2) the corrosion resistance of the Zr-doped UO 2 fuel in the hightemperature water or steam is very excellent, and (3) the thermal conductivity of Zr-doped UO 2 fuel remains relatively unchanged with irradiation, even though it is somewhat lower than the pure UO 2 fuel.…”

Section: Introductionmentioning

confidence: 99%

Effects of Zr doping on the surface energy and surface structure of UO2: Atomistic simulations

Xiao

Long

Chen

et al. 2015

Applied Surface Science

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“…It is known that the electric conductivity of neat UO 2 is lower than that of UO 2 containing impurities. [11][12][13][14] Therefore, presence of such a neat UO 2 matrix on the dissolved surface brings to a decrease in the dissolution rate. Moreover, in garvanostatic electrolysis, a decrease of the electric conductivity leads to the increase in potential.…”

Section: Analyses Of the Surface Of The Simulated Fuel Pelletmentioning

confidence: 99%

“…It is known that electric conductivity of UO 2 is caused by non-stoichiometric and defective structures, and is promoted by presence of impurities. [11][12][13][14] Therefore, anodic dissolution of uranium component in spent fuels should be done more easily than neat UO 2 , because FP in the spent fuels play a role of impurities.…”

Section: Introductionmentioning

confidence: 99%

Anodic Dissolution of UO₂Pellet Containing Simulated Fission Products in Ammonium Carbonate Solution

Asanuma

Harada

Nogami³

et al. 2006

Journal of Nuclear Science and Technology

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We have proposed a reprocessing process based on the dissolution of spent fuels in aqueous carbonate solution. In order to develop such a reprocessing process, anodic dissolution experiments were carried out by using a simulated spent fuel pellet in (NH 4 ) 2 CO 3 solution. The dissolution rate constant of the simulated fuel pellet at 323 K was estimated as 3:1Â10 À6 molÁcm À2 Ámin À1 , which is comparable to that in 5 molÁdm À3 HNO 3 solution containing 0.01 molÁ dm À3 HNO 2 at 323 K. The dissolution rate and the current efficiency for the dissolution of simulated fuel pellet in (NH 4 ) 2 CO 3 solution were found to decrease with the elapse of time. Furthermore, in order to examine dissolution behavior, the surface conditions of the pellet before and after the dissolution experiments were analyzed with the scanning electron microscopy and the energy dispersive X-ray spectroscopy. It was found that neat UO 2 matrix exists on the dissolved surface and a decrease in the dissolution rate and the current efficiency is caused by the increase in such surface area on the pellet.During the dissolution experiments, precipitates of the simulated fission products were observed on the pellet and in (NH 4 ) 2 CO 3 solution used as the electrolytic solution. Analyses of the electrolytic solution revealed that most of the simulated fission products, i.e. alkaline earth and rare earth elements, are precipitated in high ratios. From these results, it is expected that the anodic dissolution of spent fuels and the separation of fission products by precipitation can be performed simultaneously.

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Oxygen potential, electrical conductivity and defect structure of titanium-doped uranium dioxide

Cited by 22 publications

References 18 publications

Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral–Orthorhombic Transition in SrUO₄

Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral–Orthorhombic Transition in SrUO₄

Effects of Zr doping on the surface energy and surface structure of UO2: Atomistic simulations

Anodic Dissolution of UO₂Pellet Containing Simulated Fission Products in Ammonium Carbonate Solution

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Oxygen potential, electrical conductivity and defect structure of titanium-doped uranium dioxide

Cited by 22 publications

References 18 publications

Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral–Orthorhombic Transition in SrUO4

Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral–Orthorhombic Transition in SrUO4

Effects of Zr doping on the surface energy and surface structure of UO2: Atomistic simulations

Anodic Dissolution of UO2Pellet Containing Simulated Fission Products in Ammonium Carbonate Solution

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Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral–Orthorhombic Transition in SrUO₄

Nonstoichiometry in Strontium Uranium Oxide: Understanding the Rhombohedral–Orthorhombic Transition in SrUO₄

Anodic Dissolution of UO₂Pellet Containing Simulated Fission Products in Ammonium Carbonate Solution