Effects of Th doping on mechanical properties of U1–xThxO2: An atomistic simulation

Xin Yong; Bao Hong-Wei; Sun Zhi-Peng; Zhang Ji-Bin; Liu Shi-Chao; Guo Zi-Xuan; Wang Hao-Yu; Ma Fei; Li Yuan-Ming

doi:10.7498/aps.70.20202239

Abstract

Since thorium (Th) owns high conversion ratio in thermal neutron spectrum, high melting temperature, high thermal conductivity and good corrosion resistance in high-temperature water, it can be doped into UO₂ based fuel to initiate the fission reaction, and improve the physical properties of UO₂. Owing to the challenging experimental conditions and technologies, molecular dynamics (MD) simulations are conducted to investigate the influences of Th doping on the mechanical properties of U_1–_xTh_xO₂. The phase transition from initial fluorite structure to the metastable scrutinyite phase when loading along the [001] direction is observed, which accords well with the previous density functional theory calculations. However, if U_1–_xTh_xO₂ is loaded along the [111] direction, only brittle fracture is observed. It is found that both the elastic modulus and fracture stress decrease linearly with elevating temperature but the fracture strain increases. As the Th concentration increases from 0 to 0.55, the elastic modulus first decreases and then increases; if the Th concentration is larger than 0.1, the fracture stress increases and the fracture strain decreases monotonically. The cracks are nucleated with an angle of 45º to the loading direction, propagate rapidly, and are characteristic of brittle fracture, which accords well with the classical failure criteria and experimental results for brittle materials. By comparison, the uniaxial tensile loading is also performed for polycrystalline U_1–_xTh_xO₂. It is found that the elastic modulus and fracture stress decrease as the temperature increases. However, the elastic modulus is not sensitive to the Th concentration and the fracture increases as the Th concentration increases. The brittle intergranular fracture is observed in each of all polycrystalline samples. The obtained physical parameters are useful for designing the fuels in nuclear reactors.

Keywords:

Authors and contacts

1.
Science and Technology on Reactor System Design Technology Laboratory, Nuclear Power Institute of China, Chengdu 610213, China
2.
State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Corresponding author: Ma Fei, mafei@mail.xjtu.edu.cn ; Li Yuan-Ming, lym_npic@126.com

Funds: Project supported by the National Natural Science Foundation of China (Grant Nos. U20B2013, 12005213)

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References

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Cited By

图 1 U_1–_xTh_xO₂ 混合燃料模型及单轴拉伸加载示意图

Figure 1. Atomic model of U_1–_xTh_xO₂ upon uniaxial tensile loading.

DownLoad: Full-Size Img PowerPoint

图 2 UO₂与U_0.75Th_0.25O₂沿[001]和[111]方向单轴拉伸加载过程　(a) 应力-应变曲线; (b) 沿[001]拉伸过程中的径向分布函数; (c) 沿[111]拉伸过程中的径向分布函数; (d) U_0.75Th_0.25O₂沿[001]拉伸的原子结构演化; (e) U_0.75Th_0.25O₂沿[111]拉伸时的原子结构演化

Figure 2. Tensile behaviors of UO₂ and U_0.75Th_0.25O₂ along [001] and [111] direction: (a) Stress-strain curves; (b) radial distribution function (RDF, g(r)) along [001] direction; (c) RDF along [111] direction; (d) the atomic structure evolution of U_0.75Th_0.25O₂ along [001] direction; (e) the atomic structure evolution of U_0.75Th_0.25O₂ along [111] direction.

DownLoad: Full-Size Img PowerPoint

图 3 温度对U_1–_xTh_xO₂ 混合燃料沿[111]方向单轴拉伸时的力学性能的影响　(a), (b), (c) UO₂, U_0.95Th_0.05O₂及U_0.45Th_0.55O₂不同温度下的应力-应变曲线; (d), (e), (f) 对应的弹性模量随温度的变化; (g), (h), (i) 对应的断裂应力随温度的变化; (j), (k), (l) 对应的断裂应变随温度的变化

Figure 3. Effect of temperature on the mechanical properties of U_1–_xTh_xO₂ loaded along the [111] direction: (a), (b), (c) Stress-strain curves of UO₂, U_0.95Th_0.05O₂ and U_0.45Th_0.55O₂; (d), (e), (f) the corresponding elastic modulus as a function of temperature; (g), (h), (i) the corresponding fracture stress as a function of temperature; (j), (k), (l) the corresponding fracture strain as a function of temperature.

DownLoad: Full-Size Img PowerPoint

图 4 Th掺杂浓度对U_1–_xTh_xO₂ 混合燃料沿[111]方向单轴拉伸时的力学性能的影响　(a) 300 K下不同掺杂浓度时的应力-应变曲线; (b) 不同温度下弹性模量随掺杂浓度的变化; (c) 不同温度下断裂应力随掺杂浓度的变化; (d) 不同温度下断裂应变随掺杂浓度的变化

Figure 4. Effect of Th concentration on the mechanical properties of U_1–_xTh_xO₂ loaded along the [111] direction: (a) Stress-strain curves; (b) the elastic modulus as a function of Th concentration; (c) the fracture stress as a function of Th concentration; (d) the fracture strain as a function of Th concentration.

DownLoad: Full-Size Img PowerPoint

图 5 U_1–_xTh_xO₂ 混合燃料沿[111]方向单轴拉伸时的原子结构演化　(a) UO₂, 300 K; (b) UO₂, 1000 K; (c) U_0.45Th_0.55O₂, 300 K; (d) U_0.45Th_0.55O₂, 1200 K

Figure 5. Typical atomic structure evolution of U_1–_xTh_xO₂ upon tensile loading along [111] direction: (a) UO₂, 300 K; (b) UO₂, 1000 K; (c) U_0.45Th_0.55O₂, 300 K; (d) U_0.45Th_0.55O₂, 1200 K.

DownLoad: Full-Size Img PowerPoint

图 6 多晶U_1–_xTh_xO₂ 混合燃料单轴拉伸力学特性　(a) 三种掺杂浓度下不同温度时的应力-应变曲线; (b) 弹性模量随温度的变化; (c) 断裂应力随温度的变化; (d) 断裂过程中的三维结构; (e) 不同应变下三角晶界区域的放大图, 原子颜色由其应变标定

Figure 6. Mechanical behaviors of polycrystalline U_1–_xTh_xO₂: (a) Stress-strain curves for different temperature and Th concentration; (b) the elastic modulus as a function of temperature; (c) the fracture stress as a function of temperatures; (d) the three-dimensional atomic structure; (e) the atomic structure evolution around a triple grain boundary.

DownLoad: Full-Size Img PowerPoint

[1]	Rest J, Cooper M W D, Spino J, Turnbull J A, Van Uffelen P, Walker C T 2019 J. Nucl. Mater. 513 310 Google Scholar
[2]	Tonks M, Andersson D, Devanathan R, Dubourg R, El-Azab A, Freyss M, Iglesias F, Kulacsy K, Pastore G, Phillpot S R, Welland M 2018 J. Nucl. Mater. 504 300 Google Scholar
[3]	Danièle R, Barthe M F, Christophe J 2012 J. Nucl. Mater. 420 63 Google Scholar
[4]	Liu N Z, He H M, Noël J J, Shoesmith D W 2017 Electrochim. Acta 235 654 Google Scholar
[5]	Mixed Oxide (MOX) Fuel, World Nuclear Association https://www.world-nuclear.org/information-library/nuclear-fuel-cycle/fuel-recycling/mixed-oxide-fuel-mox.aspx[2021-2-3]
[6]	Murphy S T, Cooper M W D, Grimes R W 2014 Solid State Ionics 267 80 Google Scholar
[7]	Ghosh P S, Arya A, Kuganathan N, Grimes R W 2019 J. Nucl. Mater. 521 89 Google Scholar
[8]	Lee W E, Gilbert M, Murphy S T, Grimes R W, Green D J 2013 J. Am. Ceram. Soc. 96 2005 Google Scholar
[9]	Soulié A, Crocombette J P, Kraych A, Garrido F, Sattonnay G, Clouet E 2018 Acta Mater. 150 248 Google Scholar
[10]	Baena T, Cardinaels K, Govers Pakarinen J, Binnemans K, Verwerft M 2015 J. Nucl. Mater. 467 135 Google Scholar
[11]	Xiao H X, Long C, Tian X, Chen H 2016 Mater. Des. 96 335 Google Scholar
[12]	Xiao H X, Wang X, Long C, Tian X, Wang H 2017 Nucl. Eng. Technol. 49 1733 Google Scholar
[13]	Chiang T W, Chernatynskiy A, Sinnott S B, Phillpot S R 2014 J. Nucl. Mater. 448 53 Google Scholar
[14]	Lee C W, Chernatynskiy A, Shukla P, Stoller R E, Sinnott S B, Phillpot S R 2015 J. Nucl. Mater. 456 253 Google Scholar
[15]	Rahman M J, Szpunar B, Szpunar J A 2019 Comput. Mater. Sci. 166 193 Google Scholar
[16]	Calashev A Y, Ivanichkina K S, Zaikov Y P 2020 J. Solid State Chem. 286 121278 Google Scholar
[17]	Cooper M W D, Middleburgh S C, Grimes R W 2015 J. Nucl. Mater. 466 29 Google Scholar
[18]	Cooper M W D, Murphy S T, Fossati P C M, Rushton M J D, Grimes R W. 2014 Proc. R. Soc. London, Ser. A 470 20140427 Google Scholar
[19]	Balboa H, Brutzel L V, Chartier A, Le B Y 2017 J. Nucl. Mater. 495 67 Google Scholar
[20]	Rahman M J, Szpunar B, Szpunar J A 2019 J. Nucl. Mater. 513 8 Google Scholar
[21]	Rahman M J, Cooper M W D, Szpunar B, Szpunar J A, 2018 Comput. Mater. Sci. 169 109124
[22]	Ghosh P S, Kuganathan N, Galvin C O T, Arya A, Dey G K, Dutta B K, Grimes R W 2016 J. Nucl. Mater. 479 112 Google Scholar
[23]	Palomares R I, McDonnell M T, Yang L, Yao T K, Szymanowski J E S, Neuefeind J, Sigmon G E, Lian J, Tucker M G, Wirth B D, Lang M 2019 Phys. Rev. Mater. 3 053611 Google Scholar
[24]	Canon R F, Roberts J T A, Beals R J 1971 J. Am. Ceram. Soc. 54 105 Google Scholar
[25]	Kapoor K, Ahmad A, Laksminarayana A, Rao G V S H 2007 J. Nucl. Mater. 366 87 Google Scholar
[26]	Arayro J, Treglia G, Ribeiro F 2016 J. Phys. Condens. Matter. 28 015006 Google Scholar
[27]	Mo K, Miao Y B, Xu R Q, Yao T K, Lian J, Jamison L M, Yacout A M 2020 J. Nucl. Mater. 529 151943 Google Scholar
[28]	Desai T G, Millett P C, Wolf D 2008 Acta Mater. 56 4489 Google Scholar
[29]	Tian X F, Ge L Q, Yu Y, Wang Y, You Z J, Li L S 2019 J. Alloys Compd. 803 42 Google Scholar
[30]	Zhang Y F, Liu X Y, Millett P C, Tonksa M, Andersson D A, Bine B 2012 J. Nucl. Mater. 430 96 Google Scholar
[31]	Lunev A V, Kuksin A Y, Starikov S V 2017 Int. J. Plast. 89 85 Google Scholar
[32]	Idiri M, Bihan T. L, Heathman S, Rebizant J 2004 Phys. Rev. B 70 014113 Google Scholar
[33]	Tian X F, Wang Y, Ge L Q, Dong W J, You Z J, Dinga P P, Yu Y 2019 Comput. Mater. Sci. 169 109124 Google Scholar
[34]	Fossati P C M, Brutzel L V, Chartier A 2013 Phys. Rev. B 88 214112 Google Scholar
[35]	Malakkal L, Prasad A, Jossou E, Ranasinghe J, Szpunar B, Bichler L, Szpunar J 2019 J. Alloys Compd. 798 507 Google Scholar
[36]	Cereceda D, Perlado, J M, Marian J 2012 Comput. Mater. Sci. 62 272 Google Scholar
[37]	Meng L J, Jiang J, Wang J L, Ding F 2014 J. Phys. Chem. C 118 720 Google Scholar
[38]	Stukowski A 2010 Modell. Simul. Mater. Sci. Eng. 18 015012 Google Scholar
[39]	Varshni Y P 1970 Phys. Rev. B 2 3952 Google Scholar
[40]	Feng L, Sarah C F, Brent H, Shen J D, Andrew T N 2020 JOM 72 5 Google Scholar

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Effects of Th doping on mechanical properties of U_1–_xTh_xO₂: An atomistic simulation