Preliminary Analysis of Fission-Induced Dimensional Changes in Single Crystals of Uranium

Paine, S.H.; Kittel, J.H.

doi:10.2172/4282942

Cited by 7 publications

(7 citation statements)

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“…One relevant behavior is the anisotropic irradiation growth of α-U (Leggett et al, 1963), which can lead to the tearing along grain boundaries and the formation of crystallographically aligned pores. These porosities are believed to form due to the interaction of lattice defects and stresses induced by irradiation and a temperature gradient and result in significant volume changes of α-U (Paine and Kittel, 1958;Leggett et al, 1963). A full understanding of the relationship between point defects, lattice strains, and the generation of pores, has not been established either experimentally or via computational methods.…”

Section: Introductionmentioning

confidence: 99%

Determination of Thermal Expansion, Defect Formation Energy, and Defect-Induced Strain of α-U Via ab Initio Molecular Dynamics

et al. 2021

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Uranium (U) is often alloyed with molybdenum (Mo) or zirconium (Zr) in order to stabilize its high-temperature body-centered cubic phase for use in nuclear reactors. However, in all metallic fuel forms, the α phase of U remains in some fraction. This phase decomposition due to temperature or compositional variance can play an outsized role on fuel performance and microstructural evolution. Relatively little is known about fundamental point defect properties in α-U at non-zero temperatures, from either computational or experimental studies. This work performs the first thorough evaluation of the α phase of U via ab initio molecular dynamics (AIMD). A number of thermophysical properties are calculated as a function of temperature, including equilibrium lattice parameters, thermal expansion, and heat capacity. These results indicate a two-region behavior, with the transition at 400 K. The thermal expansion/contraction in the a/b direction occurs rapidly from 100 up to 400 K, after which a more linear and gradual change in the lattice constant takes place. The volumetric expansion matches experiments quantitatively, but the individual lattice constant expansion only matches experiments qualitatively. Point defect formation energies and induced lattice strains are also determined as a function of temperature, providing insight on defect populations and the fundamentals of irradiation growth in α-U. Interstitials induce significantly more strain than vacancies, and the nature of that strain is highly dependent on the individual lattice directions. The direction of point defect-induced lattice strain is contrary to the irradiation growth behavior of α-U. This work shows that isolated point defects cannot be the primary driving force responsible for the significant irradiation-induced growth of α-U observed experimentally.

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Section: Introductionmentioning

confidence: 99%

Determination of Thermal Expansion, Defect Formation Energy, and Defect-Induced Strain of α-U Via ab Initio Molecular Dynamics

et al. 2021

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“…0 because twinning is not expected to operate under compressive stress. The critical resolved shear stress is given as [15,16] τ α c = Γ τ α 0 + τ α f or + τ α sub (6) where τ α c is the friction stress, τ α f or is the stress arising from the presence of forest dislocations, τ α sub is the stress arising from the presence of a dislocation substructure, and Γ is a temperature-dependent factor for hardening. The stress from forest dislocations is given as [15]…”

Section: Modelsmentioning

confidence: 99%

“…∂β is a constant for irradiation induced growth strain and β is the burnup. The irradiationinduced growth strain is related to the growth coefficients G i [6] as…”

Section: Modelsmentioning

confidence: 99%

“…The swelling mechanism is hypothesized to be mechanical cavitation resulting from irradiation-induced shape changes of αuranium crystals. Irradiation (i.e., fuel burnup) causes single crystals of α-uranium to change shape macroscopically, shrinking in the [100] direction, growing in the [010] direction, and unchanged in the [001] direction [6].…”

Section: Introductionmentioning

confidence: 99%

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Lower length scale informed improvements to Bison U-Pu-Zr fuel swelling model

Aagesen

Jokisaari

2020

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Due to renewed interest in metallic fuels from the U-(Pu)-Zr material system, significant improvements have recently been made to BISON's capability to simulate metallic fuel, particularly in the area of swelling. In this report, lower length scale simulations that have been conducted to inform the engineering-scale models in BISON during FY20 are described. For the high-temperature regions of the fuel that are dominated by the γ phase of U-(Pu)-Zr, two new models for swelling have implemented in BISON. Phase-field simulations were conducted to calculate parameters for these and other BISON models that control when gaseous swelling ceases and fission gas release begins. For the low-temperature regions of the fuel dominated by the α phase of uranium, microstructurally resolved simulations of pore growth and crystal deformation were performed to understand the effect of irradiation-generated crystal shape changes. Conformally meshed microstructures with pores were simulated with a crystal plasticity model and with a burnup eigenstrain model. Plastic deformation will not cause pore size to increase; burnup eigenstrain (irradiation-induced crystal shape changes) will increase the volume of existing porosity and cause it to become anisotropic in shape. Additional model development work for early-stage fission gas cluster/bubble formation in the γ phase were performed, by coupling with defect clustering within cluster dynamics framework. Sensitivity analysis were conducted to identify the critical thermo-kinetic parameters needed for rigorous assessment.

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“…The U-5Fs metal alloy provided sufficient phase stability, irradiation growth resistance, and allowable operating temperature range for irradiation in EBR-II, so long as the metal fuel did not exhibit a crystallographic texture that led to anisotropic growth during irradiation [27,28]. Crystallographic texture is commonly referred to as preferred orientation of grains (i.e.…”

Section: Ebr-iimentioning

confidence: 99%

A US perspective on fast reactor fuel fabrication technology and experience part I: metal fuels and assembly design

Burkes

Fielding

Porter

et al. 2009

Journal of Nuclear Materials

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Preliminary Analysis of Fission-Induced Dimensional Changes in Single Crystals of Uranium

Cited by 7 publications

References 1 publication

Determination of Thermal Expansion, Defect Formation Energy, and Defect-Induced Strain of α-U Via ab Initio Molecular Dynamics

Determination of Thermal Expansion, Defect Formation Energy, and Defect-Induced Strain of α-U Via ab Initio Molecular Dynamics

Lower length scale informed improvements to Bison U-Pu-Zr fuel swelling model

A US perspective on fast reactor fuel fabrication technology and experience part I: metal fuels and assembly design

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