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Title: Development of molecular dynamics potential for uranium silicide fuels

Abstract

Use of uranium–silicide (U-Si) in place of uranium dioxide (UO2) is one of the promising concepts being proposed to increase the accident tolerance of nuclear fuels. This is due to a higher thermal conductivity than UO2 that results in lower centerline temperatures. U-Si also has a higher fissile density, which may enable some new cladding concepts that would otherwise require increased enrichment limits to compensate for their neutronic penalty. However, many critical material properties for U-Si have not been determined experimentally. For example, silicide compounds (U3Si2 and U3Si) are known to become amorphous under irradiation. There was clear independent experimental evidence to support a crystalline to amorphous transformation in those compounds. However, it is still not well understood how the amorphous transformation will affect on fuel behavior. It is anticipated that modeling and simulation may deliver guidance on the importance of various properties and help prioritize experimental work. In order to develop knowledge-based models for use at the engineering scale with a minimum of empirical parameters and increase the predictive capabilities of the developed model, inputs from atomistic simulations are essential. First-principles based density functional theory (DFT) calculations will provide the most reliable information. However, it is probably not possiblemore » to obtain kinetic information such as amorphization under irradiation directly from DFT simulations due to size and time limitations. Thus, a more feasible way may be to employ molecular dynamics (MD) simulation. Unfortunately, so far no MD potential is available for U-Si to discover the underlying mechanisms. Here, we will present our recent progress in developing a U-Si potential from ab initio data. This work is supported by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program funded by the U.S. Department of Energy, Office of Nuclear Energy.« less

Authors:
; ;
Publication Date:
Research Org.:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE)
OSTI Identifier:
1358201
Report Number(s):
INL/CON-16-37586
DOE Contract Number:
DE-AC07-05ID14517
Resource Type:
Conference
Resource Relation:
Conference: Top Fuel 2016, Boise, ID, September 11–16, 2016
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; accident tolerance fuels; density functional theory; molecular dynamics potential; uranium–silicide

Citation Formats

Yu, Jianguo, Zhang, Yongfeng, and Hales, Jason D. Development of molecular dynamics potential for uranium silicide fuels. United States: N. p., 2016. Web.
Yu, Jianguo, Zhang, Yongfeng, & Hales, Jason D. Development of molecular dynamics potential for uranium silicide fuels. United States.
Yu, Jianguo, Zhang, Yongfeng, and Hales, Jason D. 2016. "Development of molecular dynamics potential for uranium silicide fuels". United States. doi:. https://www.osti.gov/servlets/purl/1358201.
@article{osti_1358201,
title = {Development of molecular dynamics potential for uranium silicide fuels},
author = {Yu, Jianguo and Zhang, Yongfeng and Hales, Jason D.},
abstractNote = {Use of uranium–silicide (U-Si) in place of uranium dioxide (UO2) is one of the promising concepts being proposed to increase the accident tolerance of nuclear fuels. This is due to a higher thermal conductivity than UO2 that results in lower centerline temperatures. U-Si also has a higher fissile density, which may enable some new cladding concepts that would otherwise require increased enrichment limits to compensate for their neutronic penalty. However, many critical material properties for U-Si have not been determined experimentally. For example, silicide compounds (U3Si2 and U3Si) are known to become amorphous under irradiation. There was clear independent experimental evidence to support a crystalline to amorphous transformation in those compounds. However, it is still not well understood how the amorphous transformation will affect on fuel behavior. It is anticipated that modeling and simulation may deliver guidance on the importance of various properties and help prioritize experimental work. In order to develop knowledge-based models for use at the engineering scale with a minimum of empirical parameters and increase the predictive capabilities of the developed model, inputs from atomistic simulations are essential. First-principles based density functional theory (DFT) calculations will provide the most reliable information. However, it is probably not possible to obtain kinetic information such as amorphization under irradiation directly from DFT simulations due to size and time limitations. Thus, a more feasible way may be to employ molecular dynamics (MD) simulation. Unfortunately, so far no MD potential is available for U-Si to discover the underlying mechanisms. Here, we will present our recent progress in developing a U-Si potential from ab initio data. This work is supported by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program funded by the U.S. Department of Energy, Office of Nuclear Energy.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 9
}

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  • Use of uranium–silicide (U-Si) in place of uranium dioxide (UO2) is one of the promising concepts being proposed to increase the accident tolerance of nuclear fuels. This is due to a higher thermal conductivity than UO2 that results in lower centerline temperatures. U-Si also has a higher fissile density, which may enable some new cladding concepts that would otherwise require increased enrichment limits to compensate for their neutronic penalty. However, many critical material properties for U-Si have not been determined experimentally. For example, silicide compounds (U3Si2 and U3Si) are known to become amorphous under irradiation. There was clear independent experimentalmore » evidence to support a crystalline to amorphous transformation in those compounds. However, it is still not well understood how the amorphous transformation will affect on fuel behavior. It is anticipated that modeling and simulation may deliver guidance on the importance of various properties and help prioritize experimental work. In order to develop knowledge-based models for use at the engineering scale with a minimum of empirical parameters and increase the predictive capabilities of the developed model, inputs from atomistic simulations are essential. First-principles based density functional theory (DFT) calculations will provide the most reliable information. However, it is probably not possible to obtain kinetic information such as amorphization under irradiation directly from DFT simulations due to size and time limitations. Thus, a more feasible way may be to employ molecular dynamics (MD) simulation. Unfortunately, so far no MD potential is available for U-Si to discover the underlying mechanisms. Here, we will present our recent progress in developing a U-Si potential from ab initio data. This work is supported by the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program funded by the U.S. Department of Energy, Office of Nuclear Energy.« less
  • Recent experimental observations on low temperature swelling of irradiated uranium silicide dispersion fuels have indicated that the growth of fission gas bubbles appears to be affected by fission rate. The swelling curve of the material exhibits a distinct knee'' that shifts to higher fission density with increased fission rate due to higher enrichments. Current state-of-the-art models for fission gas behavior do not predict such a dependence. Indirect evidence from various experiments leads the present authors to speculate that a dense network of subgrain boundaries forms at a dose corresponding to the knee'' in the swelling curve, upon which gas bubblesmore » nucleate and then grow at an accelerated rate compared to those in the bulk material. A theoretical formulation is presented wherein the stored energy in the material is concentrated on a network of crystallization'' sites which diminish with dose due to interaction with radiation produced defects (vacancy-impurity pairs). Recrystallization is induced by statistical fluctuations when the energy per site is high enough such that the creation of grain boundary surfaces is offset by the creation of strain free volumes with a resultant net decrease in the free energy of the material. This formulation is shown to provide a reasonable interpretation of the observed phenomena. 11 refs., 7 figs.« less
  • While developing KMRR fuel fabrication technology an atomizing technique has been applied in order to eliminate the difficulties relating to the tough property of U{sub 3}Si and to take advantage of the rapid solidification effect of atomization. The comparison between the conventionally comminuted powder dispersion fuel and the atomized powder dispersion fuel has been made. As the result, the processes, uranium silicide powdering and heat treatment for U{sub 3}Si transformation, become simplified. The workability, the thermal conductivity and the thermal compatibility of fuel meat have been investigated and found to be improved due to the spherical shape of atomized powder.more » In this presentation the overall developments of atomized U{sub 3}Si dispersion fuel and the planned activities for applying the atomizing technique to the real fuel fabrication are described.« less
  • This report summarizes the progress on the interatomic potential development of triuranium-disilicide (U 3Si 2) for molecular dynamics (MD) simulations. The development is based on the Tersoff type potentials for single element U and Si. The Si potential is taken from the literature and a Tersoff type U potential is developed in this project. With the primary focus on the U 3Si 2 phase, some other U-Si systems such as U 3Si are also included as a test of the transferability of the potentials for binary U-Si phases. Based on the potentials for unary U and Si, two sets ofmore » parameters for the binary U-Si system are developed using the Tersoff mixing rules and the cross-term fitting, respectively. The cross-term potential is found to give better results on the enthalpy of formation, lattice constants and elastic constants than those produced by the Tersoff mixing potential, with the reference data taken from either experiments or density functional theory (DFT) calculations. In particular, the results on the formation enthalpy and lattice constants for the U 3Si 2 phase and lattice constants for the high temperature U 3Si (h-U 3Si) phase generated by the cross-term potential agree well with experimental data. Reasonable agreements are also reached on the elastic constants of U 3Si 2, on the formation enthalpy for the low temperature U 3Si (m-U 3Si) and h-U 3Si phases, and on the lattice constants of m-U 3Si phase. All these phases are predicted to be mechanically stable. The unary U potential is tested for three metallic U phases (α, β, γ). The potential is found capable to predict the cohesive energies well against experimental data for all three phases. It matches reasonably with previous experiments on the lattice constants and elastic constants of αU.« less
  • The world will continue to rely on liquid fuels to fulfill the world's transportation energy needs. The demonstrated coal reserves in the world would last for 220 years at the world's annual consumption rate in 1996, while the known oil reserves as of 1997 would last a mere 40 years at the world's consumption rate of 1996. Thus the conversion of coal derived liquids into transportation fuels will be an area of long-term research. Heightened awareness and knowledge on the detrimental effects of automobile emissions and pollution from liquid fuels has led society to articulate its desire for improved airmore » quality through stringent environmental regulations concerning fuel quality. These fuel quality standards are getting all the more stringent. A specific example is that of sulfur content in diesel; the now common sulfur content of 500 wppm is set to come down to 30 wppm. Coal derived liquids will, thus, require extensive processing and one important process is hydrotreating. Such fuel quality standards will make the task of hydrotreating at refineries technologically more challenging. One promising approach is to develop hydrotreating catalysts with steep increase in activity. In 1992 researchers at Mobil Technology Company invented a new class of molecular sieves with pore diameters of 2--15 nm, i.e., mesoporous in nature. These mesoporous molecular sieves have high surface area in uniform mesopores and are expected to be of importance in hydroprocessing liquids, which contain large heteroatom-containing molecules such as alkylated dibenzothiophenes. This paper reviews research initiatives, with some of the earliest ones emerging from this laboratory, in the use of mesoporous aluminosilicate-supported catalysts for hydrogenation and hydrotreating.« less