Oxidation behavior of unirradiated UO2 pellets

Bae, Ki Kwang; Kim, B.G.; Lee, Y.W.; Yang, Mino; Park, Hee Sung

doi:10.1016/0022-3115(94)90263-1

Cited by 37 publications

(18 citation statements)

References 10 publications

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“…A post-oxidation examination using SEM shows that the nanometric powder is not cracked contrarily to the other powders. On the contrary, a post-oxidation Contrarily to Bae et al ex situ analysis, 8 spalling was not observed during the in situ ESEM experiments. With ESEM, samples did not need to be handled in order to perform observations, but they turned to powder as soon as they were removed out ESEM.…”

Section: Comparison Between Morphologic Evolution and Kinetic Curves contrasting

confidence: 63%

“…They showed that the oxidation kinetics can be described by a rate-limiting step of growth which does not change the over all reaction. But, thanks to a comparative study of UO 2 pellet morphology and their weight gain curves, Bae et al 8 stated that, for pellet oxidised at 400 • C, "after incubation time, crack propagation rate could control the constant oxidation rate". Considering these two papers, the physical origin of the sigmoid curve remains unclear and controversial.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the origin of the sigmoid shape in the UO2 oxidation weight gain curves

Quémard

Desgranges

Bouineau

et al. 2009

Journal of the European Ceramic Society

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International audienceCracking and spalling are known to occur during the oxidation of UO2. However, these phenomena are not considered by the existing kinetic models of the oxidation of UO2 into U3O8. In this study the oxidation of UO2 samples of various sizes from the single crystal to nanopowders, has been followed by isothermal and isobaric thermogravimetry, environmental scanning electron microscopy and in situ X-ray diffraction at temperatures ranging from 250 to 370°C in air. It has been shown that cracking occurs once a critical layer thickness of intermediate oxide has been reached, which corresponds to the beginning of the sigmoid kinetic curve. Cracking contribution to the sigmoid kinetic curve is then discussed as a function of temperature, and on the basis of nucleation and growth processes

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Section: Comparison Between Morphologic Evolution and Kinetic Curves contrasting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

On the origin of the sigmoid shape in the UO2 oxidation weight gain curves

Quémard

Desgranges

Bouineau

et al. 2009

Journal of the European Ceramic Society

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show abstract

“…And the reaction rate considerably decreases at the low temperature of 325 C. The oxidation of UO 2 in air to U 3 O 8 is a multistep reaction. [9][10][11][12][13][14][15] The UO 2 is oxidized to U 3 O 8 via intermediate phases of U 4 O 9 and U 3 O 7 , or a mixture of these two phases. 7,9,11,[13][14][15] The formation of U 3 O 7 /U 4 O 9 on UO 2 shows diffusion-controlled kinetics and follows the discretelayer mechanism.…”

Section: Methodsmentioning

confidence: 99%

Recycling Process for Sinter-Active U3O8 Powders

Yang

Kang

KIM

et al. 2010

J. Nucl. Sci. Technol.

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The effect of the oxidation temperature of UO 2 pellets on the powder properties of oxidized U 3 O 8 powders has been investigated. The powder morphology, crystalline size, and BET surface area of recycled U 3 O 8 could be modified by controlling the oxidation temperature of the UO 2 pellets. Recycled U 3 O 8 powder with a high BET surface area and a small particle size could be obtained by lowering the oxidation temperature. It was also found that this low-temperature-oxidized sinter-active U 3 O 8 powder is effective in mitigating the density drop of the UO 2 pellets when the recycled U 3 O 8 powder is added. Moreover, the recycled powder acted as a grain-size-enlarging promoter in the UO 2 pellets.

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“…This seems to be related to the specific surface area of the oxidized U 3 O 8 powders. Bae et al 9) reported that the specific surface area of the oxidized powder decreased with an increase in oxidation temperature. The high specific surface area of the oxidized powders showed the poor compactability and good sinterability of the pellet.…”

Section: Evolution Of Reoxidized U 3 O 8 Powder Morphologymentioning

confidence: 99%

Improvement of UO2 Pellet Properties by Controlling the Powder Morphology of Recycled U3O8 Powder

Kang

Yang

KIM

et al. 2008

J. Nucl. Sci. Technol.

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Powder morphology evolution of recycled U 3 O 8 according to the thermal treatments has been studied. The defective UO 2 pellets are oxidized to U 3 O 8 powders at a conventional temperature of 350 or 450 C in air. Those powders are pressed into green pellets and then sintered at 1,500 and 1,730 C in H 2 gas flow. Final reoxidized U 3 O 8 powers are obtained by reoxidizing those sintered pellets at 450 C in air. This paper shows that the reoxidized U 3 O 8 powder morphology and the BET surface areas are greatly dependent on the density of sintered UO 2 pellets before reoxidation. Reoxidized U 3 O 8 powders are added to virgin UO 2 powders to fabricate UO 2 pellets and the effect of such addition on the UO 2 pellet properties is investigated. The reoxidized U 3 O 8 powders having a certain range of BET surface area significantly promote the grain growth of UO 2 pellets.

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Oxidation behavior of unirradiated UO2 pellets

Cited by 37 publications

References 10 publications

On the origin of the sigmoid shape in the UO2 oxidation weight gain curves

On the origin of the sigmoid shape in the UO2 oxidation weight gain curves

Recycling Process for Sinter-Active U3O8 Powders

Improvement of UO2 Pellet Properties by Controlling the Powder Morphology of Recycled U3O8 Powder

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