First-principles calculations of the stability and incorporation of helium, xenon and krypton in uranium

Beeler, Benjamin; Good, Brian S.; Rashkeev, Sergey N.; Deo, Chaitanya; Baskes, M. I.; Okuniewski, Maria A.

doi:10.1016/j.jnucmat.2011.08.014

Cited by 24 publications

(26 citation statements)

References 17 publications

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“…The elastic interaction among gas bubbles and the cladding constraint in monolithic fuels might be important for gas bubble nucleation as well as growth kinetics. Thermodynamic and kinetic properties of UMo alloys and defects including Xe, vacancies, and U interstitials in bcc U single crystals have been investigated by experiments [25][26][27][28] and theoretical simulations with density functional theory (DFT) [29][30][31][32][33] and the molecular dynamics (MD) method [31,[34][35][36]. The results show that Xe substitution is stable; the dumbbell configurations of U interstitials along [100] and [110] are energetically favored; and the migration barrier of U interstitials is about 0.1 eV, which is much smaller than that of vacancies (0.5eV).…”

Section: Gas Bubble Structures Have Been Examined In Post-irradiationmentioning

confidence: 99%

Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

Hu¹,

Burkes²,

Lavender³

et al. 2016

Journal of Nuclear Materials

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Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the formation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was developed. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn't cause the gas bubble alignment, and fast 1-D migration of interstitials along <110> directions in the body-centered cubic U matrix causes the gas bubble alignment along <110> directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of an fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

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Section: Gas Bubble Structures Have Been Examined In Post-irradiationmentioning

confidence: 99%

Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

Hu¹,

Burkes²,

Lavender³

et al. 2016

Journal of Nuclear Materials

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“…The properties of defectsin bcc U single crystals have been investigated via experiments [4,[11][12][13], density functional theory (DFT) [14][15][16][17][18], and molecular dynamics (MD) method [1,16,19,20].The results show that 1) Xe is stableas a substitutional defect, and Xe migrates through vacancy-assisted mechanisms, presumably as a complex consisting of one Xe and two vacancies (XeV 2 complex), 2) the dumbbell configurations of U interstitials along the [100] or [110] direction are energetically favored, and 3) the migration barrier of U interstitials is about 0.1 eV, which is much smaller than that of vacancies (0.5eV).The defect generation and spatial distribution during cascades in bcc U were simulated using MD methods [21,22].The results show that most of the surviving interstitials form a [100] or [110] dumbbell.Almost all the interstitials remain isolated, while vacancies tend to cluster into polyhedral voids [22].The equation of state (EOS) of the Xe gas phase has been examined by experiments [23][24][25] and atomistic simulations [26]. Very recently, Xiao et al simulated the pressure inside Xe bubbles with different Xe concentrations in bcc U10Mo alloys [27].…”

Section: Introductionmentioning

confidence: 99%

Atomistic simulations of thermodynamic properties of Xe gas bubbles in U10Mo fuels

Joshi

Lavender

2017

Journal of Nuclear Materials

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Xe gas bubble superlattice formation is observed in irradiated uranium-10 wt% molybdenum (U10Mo) fuels. However, the thermodynamic properties of the bubbles(the relationship among bubble size, equilibrium Xe concentration, and bubble pressure)and the mechanisms of bubble superlattice formation are not well known.In this work, the molecular dynamics (MD) method is used to study these properties and mechanisms. The results provide important inputs for quantitative mesoscale models of gas bubble evolution and fuel performance. In the MD simulations, the embedded-atom method (EAM) potential of U10Mo-Xe[1] is employed. Initial gas bubbles with a low Xeconcentration(underpressured) are generated in a body-centered cubic(bcc)U10Mo single crystal.Then Xeatoms aresequentiallyadded into the bubbles one by one, and the evolution of pressure and dislocation emission around the bubbles is analyzed. The relationship between pressure, equilibrium Xe concentration, and radiusofthe bubblesis established.It was found that an overpressuredgas bubble emits partial dislocations witha Burgers vector along the <111> direction and a slip plane of (11-2). Meanwhile, dislocation loop punchout was not observed.The overpressured bubble also induces an anisotropic stress field. A tensile stress was found along <110> directions around the bubble, favoring the nucleation and formation of aface-centered cubic bubble superlattice in bccU10Mo fuels.

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“…The present contribution focuses on the effect of grain boundary embrittlement of sulfur segregation at a nickel grain boundary [23,24]. Precipitation and segregation to GBs are related to the diffusion barrier of the elements.…”

Section: Introductionmentioning

confidence: 99%

Stress effects on stability and diffusion behavior of sulfur impurity in nickel: A first-principles study

Dong

Zhang

Liu

et al. 2014

Computational Materials Science

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a b s t r a c tA systematic investigation regarding the effect of stress on the stability and diffusion behavior of S impurity in Ni was carried out via first-principles methods. A comparison of the formation energy of S in Ni indicated that S more easily forms as a solution atom with increasing S concentration in Ni supercells, but the binding energy showed that as the concentration of S that dissolved into Ni increased, the structure became less stable. The diffusion barrier via the octahedral-tetrahedral-octahedral site path was always lower than that via the octahedral-octahedral site path. The diffusion barrier of single S decreased with increase in tensile stress. S diffusion accelerated under applied tensile stress, which was disadvantageous in suppressing S retention in Ni. These results implied that even at a low concentration, dissolved S still had a tendency of precipitating from the Ni matrix, to further increase the stability of the system.

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First-principles calculations of the stability and incorporation of helium, xenon and krypton in uranium

Cited by 24 publications

References 17 publications

Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

Atomistic simulations of thermodynamic properties of Xe gas bubbles in U10Mo fuels

Stress effects on stability and diffusion behavior of sulfur impurity in nickel: A first-principles study

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