Quantitative Characterisation of Structure in Nuclear Graphite

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The aim of this PhD research is to establish reliable/novel approaches to quantify the key structural features inside nuclear graphite. Such quantitative characterisation is essential for underpinning true mechanisms governing neutron irradiation-induced and/or -assisted damage and deformation of nuclear graphite under different loading and temperature conditions. Such evidence-based mechanistic understanding will instruct the modelling of property and structure changes at a scale from atomic, nanometer, micron, up to macro. To achieve the aim, the following research topics are proposed as the main focus of the PhD researcher: (a) Pore and micro-crack structure analysis with focused ion beam microscopy. The research will focus on the quantitative analysis of 2D images and reconstructed 3D pore/micro-crack tomography structure. Advanced image analysis techniques and algorithms will be developed for quantification-based comparative studies among different graphite grades, and those with different reactor/MTR histories for the same grade. The research outcomes will be further analysed with tomography data acquired via other techniques used in other research groups. (b) Crystal structure disordering analysis by Raman and TEM. The objective of this research is to establish a non-destructive method that can quantitatively map the variation of disordered graphite crystallites, or graphene, inside nuclear graphite. Such disordering information is expected to have a strong relationship with irradiation history, i.e. neutron dosage, temperature, loading level and type, and oxidation. (c) True texture characterisation of graphite. Texture of graphite can have strong influence on the physical properties of graphite, and brings the heterogeneity in physical properties along different directions. Texture can be further evolved during irradiation, particularly with help of compression/tension loading. The PhD research will use various methods to quantitatively characterise the true texture of a nuclear graphite.