Irradiation damage in nuclear graphite at the atomic scale

Abstract Microstructures of nuclear graphite have been investigated based on the analysis of both X-ray diffraction patterns and High Resolution Transmission Electron Microscopy images (HRTEM) from experiments and from molecular dynamics simulations. One filler particle – composed of almost aligned crystallites separated by Mrozowski cracks – and the whole sequence of single crystal graphite irradiated from its virgin state up to highly damaged (64.5% of defects) have been simulated. Simulations are assessed against experiments based on the analysis of its microstructures extracted with Bragg's law and Scherrer's equation applied to simulated X-ray diffraction patterns. In particular, the evolution of cell parameters with defect concentration generated by irradiation agrees well with experimental observations. Simulated HRTEM images show many features observed in experimental images in both virgin and irradiated French nuclear graphite. Some of these features can be linked unequivocally to defined atomistic configurations. Basal grain boundaries (GBs), Mrozowski cracks, graphene sheets and their folding belong to this category. Conversely, some patterns in simulated HRTEM cannot be related to a unique atomistic configuration and might eventually give rise to misleading interpretation. This is evidenced for edge dislocations in virgin nuclear graphite as well as for residues of graphene layers in highly damaged graphite.

[1]  N. Moncoffre,et al.  Structural and nanostructural behavior of deuterium implanted Highly Ordered Pyrolytic Graphite investigated by combined High Resolution Transmission Electron Microscopy, Scanning Electron Microscopy and Raman microspectrometry , 2015 .

[2]  P. Mummery,et al.  Graphite as a core material for Generation IV nuclear reactors , 2017 .

[3]  Simon J L Billinge,et al.  Relationship between the atomic pair distribution function and small-angle scattering: implications for modeling of nanoparticles. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[4]  P. Mummery,et al.  An Understanding of Lattice Strain, Defects and Disorder in Nuclear Graphite , 2017 .

[5]  T. Burchell,et al.  Graphite: Properties and Characteristics , 2020, Comprehensive Nuclear Materials.

[6]  J. Koike,et al.  Dimensional changes in highly oriented pyrolytic graphite due to electron-irradiation , 1994 .

[7]  V. Babu,et al.  Modeling of disorder and X-ray diffraction in coal-based graphitic carbons , 1996 .

[8]  Jae-Seung Roh,et al.  Thermal Emissivity of Nuclear Graphite as a Function of its Oxidation Degree (3): Structural Study using Scanning Electron Microscope and X-Ray Diffraction , 2011 .

[9]  M. Mojtahedi,et al.  A comparison between different X-ray diffraction line broadening analysis methods for nanocrystalline ball-milled FCC powders , 2015 .

[10]  R. Brydson,et al.  Micro to nanostructural observations in neutron irradiated nuclear graphites PCEA and PCIB , 2017 .

[11]  B. Manoj.  Study of Stacking Structure of Amorphous Carbon by X-Ray Diffraction Technique , 2012, International Journal of Electrochemical Science.

[12]  J. M. Cowley,et al.  Fourier Images: I - The Point Source , 1957 .

[13]  H. Schut,et al.  Influence of neutron irradiation on the microstructure of nuclear graphite: An X-ray diffraction study , 2017 .

[14]  M. Dresselhaus,et al.  Studying disorder in graphite-based systems by Raman spectroscopy. , 2007, Physical chemistry chemical physics : PCCP.

[15]  J.-P. Da Costa,et al.  Nanoscale elasticity of highly anisotropic pyrocarbons , 2015 .

[16]  J. Rouzaud,et al.  Milled graphite as a pertinent analogue of French UNGG reactor graphite waste for a CO2 gasification-based treatment , 2015 .

[17]  H. Kawakami.  Graphite for gas cooled reactors , 1972 .

[18]  L. V. Brutzel,et al.  Atomic scale mechanisms for the amorphisation of irradiated graphite , 2015 .

[19]  Q. Ramasse,et al.  On the nature of cracks and voids in nuclear graphite , 2016 .

[20]  T. Marrow,et al.  Microcracks in nuclear graphite and highly oriented pyrolytic graphite (HOPG) , 2008 .

[21]  M. Heggie,et al.  Extended interplanar linking in graphite formed from vacancy aggregates. , 2013, Physical review letters.

[22]  M. Ferraris,et al.  Carbon as a Fusion Plasma-Facing Material , 2012 .

[23]  Mohammad H. Mofrad,et al.  Graphite , 2019, Proceedings of the VLDB Endowment.

[24]  STUDIES ON NEON IRRADIATED AMORPHOUS CARBON USING X-RAY DIFFRACTION TECHNIQUE , 2005, cond-mat/0508494.

[25]  J.C. Meyer,et al.  Atomic structure from large-area, low-dose exposures of materials: A new route to circumvent radiation damage☆ , 2014, Ultramicroscopy.

[26]  S. Muto,et al.  On the mechanism of dimensional change of neutron irradiated graphite , 1992 .

[27]  D. Butt,et al.  In situ transmission electron microscopy of electron-beam induced damage process in nuclear grade graphite , 2011 .

[28]  Steve Plimpton,et al.  Fast parallel algorithms for short-range molecular dynamics , 1993 .

[29]  J.-P. Da Costa,et al.  Structural features of pyrocarbon atomistic models constructed from transmission electron microscopy images , 2012 .

[30]  Jean-Pierre Da Costa,et al.  A time-dependent atomistic reconstruction of severe irradiation damage and associated property changes in nuclear graphite , 2017 .

[31]  J. Kai,et al.  The relationship between microstructure and oxidation effects of selected IG- and NBG-grade nuclear graphites , 2014 .

[32]  K. Niwase.  Raman Spectroscopy for Quantitative Analysis of Point Defects and Defect Clusters in Irradiated Graphite , 2012 .

[33]  H. Fujimoto.  Theoretical X-ray scattering intensity of carbons with turbostratic stacking and AB stacking structures , 2003 .

[34]  J. Rouzaud,et al.  Nanostructural characterizations of graphite waste from French gas-cooled nuclear reactors and links with 14C inventory , 2016 .

[35]  A. Stukowski.  Visualization and analysis of atomistic simulation data with OVITO–the Open Visualization Tool , 2009 .

[36]  R. Capaz,et al.  Disentangling contributions of point and line defects in the Raman spectra of graphene-related materials , 2017 .

[37]  J.-P. Da Costa,et al.  Electron irradiation of nuclear graphite studied by transmission electron microscopy and electron energy loss spectroscopy , 2015 .

[38]  R. Brydson,et al.  Thermal annealing of nuclear graphite during in-situ electron irradiation , 2017 .

[39]  J. M. Cowley,et al.  Fourier Images: III - Finite Sources , 1957 .

[40]  Marcin Wojdyr,et al.  Fityk: a general-purpose peak fitting program , 2010 .

[41]  M. Heggie,et al.  Electron microscopy of nuclear graphite: A modelling approach , 2012 .

[42]  J. Los,et al.  Intrinsic long-range bond-order potential for carbon: Performance in Monte Carlo simulations of graphitization , 2003 .

[43]  J. M. Cowley,et al.  Fourier Images: II - The Out-of-focus Patterns , 1957 .