Bubble formation and Kr distribution in Kr-irradiated UO2

He, Lingfeng; Valderrama, Billy; Hassan, Abdel-Rahman; Yu, Jianguo; Gupta, Malaya; Pakarinen, Janne; Henderson, Hunter B.; Gan, Jian; Kirk, Marquis A.; Nelson, Andrew T.; Manuel, Michele V.; El–Azab, Anter; Allen, Todd R.

doi:10.1016/j.jnucmat.2014.09.026

Cited by 34 publications

(22 citation statements)

References 47 publications

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“…This conclusion is in disagreement with the recent work of He et al [14] where formation of Kr nano-bubbles in UO 2 thin foils was followed by TEM. In this study, UO 2 samples were implanted at room temperature with krypton atoms up to a Kr-local concentration of 0.2 at.% which is close to the implantation conditions B and C used in the present work.…”

Section: Kr Incorporation In the Uo 2 Latticecontrasting

confidence: 99%

“…Based on the Kr atoms depth distribution determined by Atom Probe Tomography (APT), the authors assumed that these nano-objects are krypton bubbles. However, as pointed out by He et al [14], no Kr ion clusters have been detected during the APT analysis and as a consequence no experimental proof of Kr atoms presence within the nano-objects is provided. Based on the results shown in the present work and obtained by Sabathier et al [15], the nano-objects observed at room temperature after implantation by He et al [14] are most likely empty and Kr atoms observed by APT are located within bound Schottky defect.…”

Section: Kr Incorporation In the Uo 2 Latticementioning

confidence: 98%

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Behavior of fission gases in nuclear fuel: XAS characterization of Kr in UO2

Martin

Vathonne

Carlot

et al. 2015

Journal of Nuclear Materials

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a b s t r a c t X-ray Absorption Spectroscopy (XAS) was used to study the behavior of krypton as a function of its concentration in UO 2 samples implanted with Kr ions. For a 0.5 at.% krypton local concentration, by combining XAS results and DFT þ U calculations, we show that without any thermal treatment Kr atoms are mainly incorporated in the UO 2 lattice as single atoms inside a neutral bound Schottky defect with O vacancies aligned along the (100) direction (BSD1). A thermal treatment at 1273 K induces the precipitation of dense Kr nano-aggregates, most probably solid at room temperature. In addition, 26 ± 2% of the Kr atoms remain inside BSD1 showing that Kr-BSD1 complex is stable up to this temperature. Consequently, the (in-)solubility of krypton in UO 2 has to be re-evaluated. For high Kr concentration (8 at.%), XAS signals show that Kr atoms have precipitated in nanometer-sized aggregates with internal densities ranging between 4.15(7) g cm À3 and 3.98(5) g cm À3 even after annealing at 873 K. By neglecting the effect due to the UO 2 matrix, the corresponding krypton pressures at 300 K were equal to 2.6(3) GPa and 2.0(2) GPa, respectively. After annealing at 1673 K, regardless of the initial Kr concentration, a bi-modal distribution is observed with solid nano-aggregates even at room temperature and larger cavities only partially filled with Kr. These results are very close to those observed in UO 2 fuel irradiated in reactor. In this study we show that a rare gas can be used as a probe to investigate the defect creation and their stability in UO 2 .

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Section: Kr Incorporation In the Uo 2 Latticecontrasting

confidence: 99%

Section: Kr Incorporation In the Uo 2 Latticementioning

confidence: 98%

Behavior of fission gases in nuclear fuel: XAS characterization of Kr in UO2

Martin

Vathonne

Carlot

et al. 2015

Journal of Nuclear Materials

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“…This value of effective U corresponds to U = 4.50 eV and = 0.54 eV, which were determined in UO 2 by Yamazaki and Kotani [23] based on the analysis of X-ray photoemission spectra. To avoid local energy minima for finding low-energy 5 orbital occupations in UO 2 , the procedure of U-ramping method is used [24,25]. 2+ .…”

Section: Calculation Methods and Methodologymentioning

confidence: 99%

Near Surface Stoichiometry in UO₂: A Density Functional Theory Study

Valderrama

Henderson

et al. 2015

Journal of Chemistry

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The mechanisms of oxygen stoichiometry variation in UO 2 at different temperature and oxygen partial pressure are important for understanding the dynamics of microstructure in these crystals. However, very limited experimental studies have been performed to understand the atomic structure of UO 2 near surface and defect effects of near surface on stoichiometry in which the system can exchange atoms with the external reservoir. In this study, the near (110) surface relaxation and stoichiometry in UO 2 have been studied with density functional theory (DFT) calculations. On the basis of the point-defect model (PDM), a general expression for the near surface stoichiometric variation is derived by using DFT total-energy calculations and atomistic thermodynamics, in an attempt to pin down the mechanisms of oxygen exchange between the gas environment and defected UO 2 . By using the derived expression, it is observed that, under poor oxygen conditions, the stoichiometry of near surface is switched from hyperstoichiometric at 300 K with a depth around 3 nm to near-stoichiometric at 1000 K and hypostoichiometric at 2000 K. Furthermore, at very poor oxygen concentrations and high temperatures, our results also suggest that the bulk of the UO 2 prefers to be hypostoichiometric, although the surface is near-stoichiometric.

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“…These latter phenomena have been actively investigated by computational methods 19,45,46 and very little experimental data exist and are a subject of future work. 47,48 The stopping and range of ions in matter (SRIM) code was used to estimate the displacement damage. 49 Calculations were done using the Kinchin-Pease method and the Norgett, Robinson, and Torrens (NRT) model.…”

Section: Measurements In Ion Irradiated Materialsmentioning

confidence: 99%

Investigation of thermal transport in composites and ion beam irradiated materials for nuclear energy applications

et al. 2016

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Thermal transport in materials used for energy applications is a physical process directly tied to performance and reliability. As a result, a great deal of effort has been devoted to understanding thermal transport in materials whose ability to conduct heat is critical. Here, our objective is to discuss the utility of laser-based thermoreflectance (TR) approaches that provide microscale measurement of thermal transport. We provide several examples that implement the TR technique to investigate thermal transport in materials used in nuclear energy applications. First, we discuss utility of this technique to measure thermal conductivity in ion irradiated ceramic materials during investigations where the primary objective is to understand the impact of radiation induced crystalline structure defects on thermal transport. We also present the capability of TR approach to resolve thermal conductivity of each layer in tristructural isotropic fuel, silicon carbide fiber composites, and 2nd phase precipitates in uranium silicide. Finally, the ability to measure interface thermal resistance between adjacent layers in composites is demonstrated.

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Bubble formation and Kr distribution in Kr-irradiated UO2

Cited by 34 publications

References 47 publications

Behavior of fission gases in nuclear fuel: XAS characterization of Kr in UO2

Behavior of fission gases in nuclear fuel: XAS characterization of Kr in UO2

Near Surface Stoichiometry in UO₂: A Density Functional Theory Study

Investigation of thermal transport in composites and ion beam irradiated materials for nuclear energy applications

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Bubble formation and Kr distribution in Kr-irradiated UO2

Cited by 34 publications

References 47 publications

Behavior of fission gases in nuclear fuel: XAS characterization of Kr in UO2

Behavior of fission gases in nuclear fuel: XAS characterization of Kr in UO2

Near Surface Stoichiometry in UO2: A Density Functional Theory Study

Investigation of thermal transport in composites and ion beam irradiated materials for nuclear energy applications

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Product

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Near Surface Stoichiometry in UO₂: A Density Functional Theory Study