Modelling fracture of aged graphite bricks under radiation and temperature

Hashim, Atheer; Kyaw, Si; Sun, Wei

Abstract

The graphite bricks of the UK carbon dioxide gas cooled nuclear reactors are subjected to neutron irradiation and radiolytic oxidation during operation which will affect thermal and mechanical material properties and may lead to structural failure. In this paper, an empirical equation is obtained and used to represent the reduction in the thermal conductivity as a result of temperature and neutron dose. A 2D finite element thermal analysis was carried out using Abaqus to obtain temperature distribution across the graphite brick. Although thermal conductivity could be reduced by up to 75% under certain conditions of dose and temperature, analysis has shown that it has no significant effect on the temperature distribution. It was found that the temperature distribution within the graphite brick is non-radial, different from the steady state temperature distribution used in the previous studies [1, 2]. To investigate the significance of this non-radial temperature distribution on the failure of graphite bricks, a subsequent mechanical analysis was also carried out with the nodal temperature information obtained from the thermal analysis. To predict the formation of cracks within the brick and the subsequent propagation, a linear traction–separation cohesive model in conjunction with the extended finite element method (XFEM) is used. Compared to the analysis with steady state radial temperature distribution, the crack initiation time for the model with non-radial temperature distribution is delayed by almost one year in service, and the maximum crack length is also shorter by around 20%.

Citation

Hashim, A., Kyaw, S., & Sun, W. (2017). Modelling fracture of aged graphite bricks under radiation and temperature. Nuclear Materials and Energy, 11, 3-11. https://doi.org/10.1016/j.nme.2017.03.038

• Journal Article Type: Article
• Acceptance Date: Mar 9, 2017
• Online Publication Date: Apr 11, 2017
• Publication Date: 2017-05
• Deposit Date: Mar 9, 2017
• Publicly Available Date: Apr 11, 2017
• Journal: Nuclear Materials and Energy
• Electronic ISSN: 2352-1791
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Pages: 3-11
• DOI: https://doi.org/10.1016/j.nme.2017.03.038
• Keywords: Nuclear graphite, neutron dose, irradiation temperature, damage model, crack growth
• Public URL: https://nottingham-repository.worktribe.com/output/855626
• Publisher URL: http://www.sciencedirect.com/science/article/pii/S2352179117300017
• Additional Information: This article is maintained by: Elsevier; Article Title: Modelling fracture of aged graphite bricks under radiation and temperature; Journal Title: Nuclear Materials and Energy; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.nme.2017.03.038; Content Type: article; Copyright: © 2017 Published by Elsevier Ltd.