熔盐堆中石墨吸附氚的理论研究
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摘要
为明确石墨表面的氟、氟化氚中的氟和单空位缺陷对氚吸附的影响机理,利用第一性原理模拟研究熔盐堆中石墨对氚的吸附,研究了在完整石墨和单空位石墨表面上氢原子(离子)、氟原子(离子)、氟气分子与氟化氢分子的吸附行为。研究发现:当氟和氢同时存在的时候,氟会优先和石墨表面的碳原子成键;石墨表面的单空位促使氟化氢在单空位处解离,以化学吸附形成存在;石墨表面吸附氢(或者氚)、氟后,表面会发生畸变;可预测熔盐堆运行过程中,氚会优先在反应堆中的石墨表面的单空位等反应活性强的地方吸附、积聚。
[Background] In molten salt reactor, the graphite can adsorb a mass of tritium. Fluorine is a constituent of molten salt, and neutron irradiation can induce a number of defects on the graphite in molten salt reactor. It is necessary to study the influence of fluorine and the defects of the graphite on tritium adsorption in molten salt reactor. [Purpose] This study aims to reveal the influence mechanism of fluorine and monovacancy defect on tritium adsorption on graphite surface. [Methods] Simulation study of the adsorption behaviors of hydrogen, fluorine and hydrogen fluoride on the surfaces of perfect graphene and vacancy-defected graphene were carried out by using first-principles calculations. [Results] The results indicate that fluorine preferentially bonds with carbon atoms when hydrogen and fluorine exist at the same time. The monovacancy on graphite surface prompts hydrogen fluoride molecule to dissolve and bond with carbon atom. Moreover, the graphite surface can be distorted after adsorbing hydrogen and fluorine. [Conclusion] Tritium generated from the molten salt reactor will be preferentially adsorbed and accumulate in the regions with more reactive activities such as monovacancy.
[Background] In molten salt reactor, the graphite can adsorb a mass of tritium. Fluorine is a constituent of molten salt, and neutron irradiation can induce a number of defects on the graphite in molten salt reactor. It is necessary to study the influence of fluorine and the defects of the graphite on tritium adsorption in molten salt reactor. [Purpose] This study aims to reveal the influence mechanism of fluorine and monovacancy defect on tritium adsorption on graphite surface. [Methods] Simulation study of the adsorption behaviors of hydrogen, fluorine and hydrogen fluoride on the surfaces of perfect graphene and vacancy-defected graphene were carried out by using first-principles calculations. [Results] The results indicate that fluorine preferentially bonds with carbon atoms when hydrogen and fluorine exist at the same time. The monovacancy on graphite surface prompts hydrogen fluoride molecule to dissolve and bond with carbon atom. Moreover, the graphite surface can be distorted after adsorbing hydrogen and fluorine. [Conclusion] Tritium generated from the molten salt reactor will be preferentially adsorbed and accumulate in the regions with more reactive activities such as monovacancy.
引文
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2 U.S.DOE Nuclear Energy Research Advisory Committee and the Generation IV International Forum.A technology roadmap for generation IV nuclear energy systems[R].2002-12.GIF-002-00,http://gif.intel.gov/.
3 Mays G T.Distribution and behavior of tritium in the coolant-salt technology facility(ORNL/TM-5759)[R].Tennessee,US:Oak Ridge,1977.
4 Sohal M S.Molten-salt reactor program:semiannual progress report for period ending(ORNL-4832)[R].Tennessee,US:Oak Ridge,1972.
5皮力,刘卫,张东勋,等.用氢同位素估算氚在熔盐堆结构材料中的渗透[J].核技术,2015,38(3):030602.DOI:10.11889/j.0253-3219.2015.hjs.38.030602.PI Li,LIU Wei,ZHANG Dongxun,et al.Estimation of permeability of tritium in structural materials of molten salt reactor based on hydrogen isotope[J].Nuclear Techniques,2015,38(3):030602.DOI:10.11889/j.0253-3219.2015.hjs.38.030602.
6 Mc Neese L E.Molten salt reactor program,semi-annual progress report(ORNL-5132)[R].Tennessee,US:Oak Ridge,1976.
7黄豫,刘卫,肖德涛.熔盐堆中氚的控制和监测[J].核技术,2011,34(8):632-636.HUANG Yu,LIU Wei,XIAO Detao.Control and monitoring of tritium in molten salt reactor[J].Nuclear Techniques,2011,34(8):632-636.
8 Guillou L M,Toulhoat N,Pipon Y,et al.Deuterium migration in nuclear graphite:consequences for the behavior of tritium in CO2-cooled reactors and for the decontamination of irradiated graphite waste[J].Journal of Nuclear Materials,2015,461:72-77.DOI:10.1016/j.jnucmat.2015.03.005.
9 Atsumi H,Tanabe T,Shikama T.Bulk hydrogen retention in neutron-irradiated graphite at elevated temperatures[J].Journal of Nuclear Materials,2009,390:581-584.DOI:10.1016/j.jnucmat.2009.01.112.
10 Atsumi H,Takemura Y,Miyabe T,et al.Desorption of hydrogen trapped in carbon and graphite[J].Journal of Nuclear Materials,2013,442:746-750.DOI:10.1016/j.jnucmat.2013.03.041.
11 Li H,Yang C,Fang C,et al.Experimental study on the adsorption and desorption of tritium in the graphite materials for HTR-PM[J].Progress in Nuclear Energy,2015,85:676-681.DOI:10.1016/j.pnucene.2015.09.003.
12 Yamaguchi M,Shiga M,Kaburaki H.Grain boundary decohesion by impurity segregation in a nickel-sulfur system[J].Science,2005,307(5708):393-397.DOI:10.1126/science.1104624.
13 Lu Y,Feng Y P.Adsorptions of hydrogen on graphene and other forms of carbon structures:first principle calculations[J].Nanoscale,2011,3(6):2444-2453.DOI:10.1039/c1nr10118h.
14杨雄,曾广礼,顾晨光,等.V型凹口对液态熔盐堆用核石墨构件应力分析的影响[J].核技术,2017,40(7):070601.DOI:10.11889/j.0253-3219.2017.hjs.40.070601.YANG Xiong,ZENG Guangli,GU Chenguang,et al.Effect of V shape notch on stress analysis of nuclear graphite component for liquid molten salt reactor[J].Nuclear Techniques,2017,40(7):070601.DOI:10.11889/j.0253-3219.2017.hjs.40.070601.
15 Hohenberg P,Kohn W.Inhomogeneous electron gas[J].Physical Review,1964,136(3B):B864-B871.DOI:10.1103/Phys Rev.136.B864.
16 Kresse G.Ab-Initio molecular-dynamics for liquidmetals[J].Journal of Non-Crystalline Solids,1995,193:222-229.DOI:10.1016/0022-3093(95)00355-X.
17 Kresse G,Furthmuller J.Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set[J].Physical Review B,1996,54(16):11169-11186.DOI:10.1103/Phys Rev B.54.11169.
18 Kresse G,Hafner J.Ab initio molecular dynamics for liquid metals[J].Physical Review B,1993,47(1):558-561.DOI:10.1103/Phys Rev B.47.558.
19 Yang L,Stephen A S,Wen G Z,et al.Hydrogen-induced magnetization and tunable hydrogen storage in graphitic structures[J].Physical Review B,2008,77:134114-134121.DOI:10.1103/Phys Rev B.77.134114.
20 Liu J,Wang C,Liang T X,et al.Density functional theory investigation of oxygen interaction with boron-doped graphite[J].Applied Surface Science,2016,390:273-282.DOI:10.1016/j.apsusc.2016.08.004.
21 Perdew J P,Wang Y.Accurate and simple analytic representation of the electron-gas correlation-energy[J].Physical Review B,1992,45(23):13244-13249.DOI:10.1103/Phys Rev B.45.13244.
22 Peter T,Ruey C.Structure of graphite by neutron diffraction[J].Nature,1975,258(5531):136-137.DOI:10.1038/258136a0.
23 Gass M H,Bangert U,Bleloch A L,et al.Free-standing graphene at atomic resolution[J].Nature Nanotechnology,2008,3(11):676-681.DOI:10.1038/nnano.2008.280.
24 Meyer J C,Kisielowski C,Erni R,et al.Direct imaging of lattice atoms and topological defects in graphene membranes[J].Nano Letters,2008,8(11):3582-3586.DOI:10.1021/nl801386m.
25 Zhang W,Sun L T,Xu Z J,et al.Migration of gold atoms in graphene ribbons:role of the edges[J].Physical Review B,2010,81(12):125425-125429.DOI:10.1103/Phys Rev B.81.125425.
26 Zhang Y H,Chen Y B,Zhou K G,et al.Improving gas sensing properties of graphene by introducing dopants and defects:a first-principles study[J].Nanotechnology,2009,20(18):185504-185509.DOI:10.1088/0957-4484/20/18/185504.
27 Erni R,Rossell M D,Nguyen M T,et al.Stability and dynamics of small molecules trapped on graphene[J].Physical Review B,2010,82(16):165443-165448.DOI:10.1103/Phys Rev B.82.165443.
28 Sha X W,Jackson B.First-principles study of the structural and energetic properties of H atoms on a graphite(0001)surface[J].Surface Science,2002,496:318-330.DOI:10.1016/S0039-6028(01)01602-8.