Examining the thermal properties of unirradiated nuclear grade graphite between 750 and 2500 K

This study presents the first high temperature measurements (between 750 K and 2500 K) of thermal conductivity, thermal diffusivity, specific heat and spectral emissivity of virgin graphite samples (type IM1-24) from advanced gas-cooled reactor (AGR) fuel assembly bricks. Scanning electron microscop...

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Bibliographic Details
Published in:Journal of nuclear materials 2020-09, Vol.538, p.152176, Article 152176
Main Authors: Pavlov, T.R., Lestak, M., Wenman, M.R., Vlahovic, L., Robba, D., Cambriani, A., Staicu, D., Dahms, E., Ernstberger, M., Brown, M., Bradford, M.R., Konings, R.J.M., Grimes, R.W.
Format: Article
Language:English
Subjects:
Computed tomography
Conductivity
Emissivity
Fillers
Gas cooled reactors
Graphite
Graphitization
Heat conductivity
Heat transfer
High temperature
Manufacturing industry
Microstructure
Morphology
Nuclear fuels
Platelets (materials)
Scanning electron microscopy
Specific heat
Spectral emissivity
Thermal conductivity
Thermal diffusivity
Thermal properties
Thermodynamic properties
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Summary:This study presents the first high temperature measurements (between 750 K and 2500 K) of thermal conductivity, thermal diffusivity, specific heat and spectral emissivity of virgin graphite samples (type IM1-24) from advanced gas-cooled reactor (AGR) fuel assembly bricks. Scanning electron microscope (SEM) and X-ray computed tomography (XRT) techniques were used to verify the presence of Gilsocarbon filler particles (a characteristic microstructural feature of IM1-24 graphite). All thermal properties were investigated in two orthogonal directions, which showed the effective macroscopic thermal conductivity to be the same (to within experimental error). This can be linked to the morphology of the filler particles that consist of concentrically aligned graphitic platelets. The resulting spherical symmetry allows for heat to flow in the same manner in both macroscopic directions. The current thermal conductivity results were compared to other isotropic grade graphite materials. The significant discrepancies between the thermal conductivities of the individual grades are likely the result of different manufacturing processes yielding variations in the microstructure of the final product. Differences were identified in the filler particle size and structure, and possibly the degree of graphitization compared to other reported nuclear graphites.
ISSN:0022-3115
1873-4820
DOI:10.1016/j.jnucmat.2020.152176