Structure of different grades of nuclear graphite

Mironov, Brindusa E; Westwood, Aidan; Scott, A. J.; Brydson, Rik; Jones, Abbie

doi:10.1088/1742-6596/371/1/012017

Cited by 8 publications

(4 citation statements)

References 4 publications

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“…Prior to the examination of irradiated material, virgin PGA was examined to establish a baseline, so that any changes due to irradiation or deposition could be observed. The Raman spectra for unirradiated graphite has been widely reported and consists of two major peaks [ 32 – 34 ]. The most intense peak is at approximately 1580 cm -1 which is designated as the ‘G’ peak and is due to the E 2g mode of molecular vibration [ 35 , 36 ].…”

Section: Resultsmentioning

confidence: 99%

Examination of Surface Deposits on Oldbury Reactor Core Graphite to Determine the Concentration and Distribution of 14C

2016

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Pile Grade A graphite was used as a moderator and reflector material in the first generation of UK Magnox nuclear power reactors. As all of these reactors are now shut down there is a need to examine the concentration and distribution of long lived radioisotopes, such as 14C, to aid in understanding their behaviour in a geological disposal facility. A selection of irradiated graphite samples from Oldbury reactor one were examined where it was observed that Raman spectroscopy can distinguish between underlying graphite and a surface deposit found on exposed channel wall surfaces. The concentration of 14C in this deposit was examined by sequentially oxidising the graphite samples in air at low temperatures (450°C and 600°C) to remove the deposit and then the underlying graphite. The gases produced were captured in a series of bubbler solutions that were analysed using liquid scintillation counting. It was observed that the surface deposit was relatively enriched with 14C, with samples originating lower in the reactor exhibiting a higher concentration of 14C. Oxidation at 600°C showed that the remaining graphite material consisted of two fractions of 14C, a surface associated fraction and a graphite lattice associated fraction. The results presented correlate well with previous studies on irradiated graphite that suggest there are up to three fractions of 14C; a readily releasable fraction (corresponding to that removed by oxidation at 450°C in this study), a slowly releasable fraction (removed early at 600°C in this study), and an unreleasable fraction (removed later at 600°C in this study).

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Section: Resultsmentioning

confidence: 99%

Examination of Surface Deposits on Oldbury Reactor Core Graphite to Determine the Concentration and Distribution of 14C

2016

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“…The nano-and micro-scale pores, the size and orientation of graphite crystals and crystallites all potentially affect the measured properties of the cantilever specimens [36][37]. In general, the structure of heat-treated carbon is usually characterised in terms of the parameters, L a and L c , defined as the length and thickness of the graphite lamellae structure within the material, respectively [42].…”

Section: Crystallite Size and Orientationmentioning

confidence: 99%

Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing

Liu

Flewitt

2017

Carbon

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing AbstractThe local mechanical properties of vitreous carbon and another three porous graphite materials have been investigated using a novel in situ micro-cantilever bending approach.Vitreous carbon is used for validation of the micro-mechanical measurements. Filter graphite is a single phase material with ~52 vol.% porosity. Gilsocarbon graphite is a nuclear-grade graphite that is currently used in the advanced gas-cooled reactors in the UK with ~20 vol.% porosity in the filler particles and matrix; Pile Grade-A graphite (PGA) was extracted from a fuel brick within a Magnox reactor core with 15% weight loss due to neutron irradiation and CO 2 radiolytic oxidation. The 'true' material properties obtained at micro-scale are found to be of much higher value than those measured at the macro-scale due to different failure controlling mechanisms. In particular for the PGA graphite, the micro-mechanical tests allowed the mechanical properties of the filler particles and matrix to be measured separately.The filler particles showed a higher stiffness and flexural strength compared with the matrix indicating the different influence of neutron irradiation on these two constituents. It is demonstrated here that the local mechanical properties of carbonaceous materials with various complex microstructures and even following neutron irradiation can be successfully evaluated.

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“…Gilsocarbon is a medium grain graphite composed of spherical onion-shaped filler particles that are moulded during the manufacturing process [25]. The combination of moulding and spherical 4 particles in Gilsocarbon result in an isotropic or semi-isotropic mechanical behaviour.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of the spatial variability of material properties of Gilsocarbon and NBG-18 using random fields

Arregui-Mena

Edmondson

Margetts

et al. 2018

Journal of Nuclear Materials

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☆ This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). Characterisation of the spatial variability of material properties of Gilsocarbon and NBG-18 using random fields ☆

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Structure of different grades of nuclear graphite

Cited by 8 publications

References 4 publications

Examination of Surface Deposits on Oldbury Reactor Core Graphite to Determine the Concentration and Distribution of 14C

Examination of Surface Deposits on Oldbury Reactor Core Graphite to Determine the Concentration and Distribution of 14C

Deformation and fracture of carbonaceous materials using in situ micro-mechanical testing

Characterisation of the spatial variability of material properties of Gilsocarbon and NBG-18 using random fields

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