Modelling 3D crack propagation in ageing graphite bricks of Advanced Gas-cooled Reactor power plant

Abstract

ABSTRACT. In this paper, crack propagation in Advanced Gas-cooled Reactor (AGR) graphite bricks with ageing properties is studied using the eXtended Finite Element Method (X-FEM). A parametric study for crack propagation, including the influence of different initial crack shapes and propagation criteria, is conducted. The results obtained in the benchmark study show that the crack paths from X-FEM are similar to the experimental ones. The accuracy of the strain energy release rate computation in a heterogeneous material is also evaluated using a finite difference approach. Planar and non-planar 3D crack growth simulations are presented to demonstrate the robustness and the versatility of the method utilized. Finally, this work contributes to the better understanding of crack propagation behaviour in AGR graphite bricks and so contributes to the extension of the AGR plants' lifetimes in the UK by reducing uncertainties.

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

“…The structural integrity studies of graphite components are usually supported by stress analysis and other calculations that estimate the failure rate and lifetime of the components. In addition to stress analysis, several fracture mechanics techniques have been implemented to analyse the crack evolution in nuclear graphite components [5][6][7][8][9]. Traditionally FEM and continuum damage techniques use the mean values of material properties to perform their analyses.…”

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“…Considering the brittle behavior of this material, brittle fracture is a typical failure mechanism which usually happens after the initiation of micro-cracks in the most stressed parts of the structure, combined in some cases with a negligible amount of plasticity [1][2][3][4]. The majority of the studies focused on structural integrity of graphite components have been devoted to the investigation of cracked components by quantifying the fracture toughness under prevalent mode I loading [5][6][7]. Innovative techniques have been proposed in the literature for fracture assessment of isotropic graphite under mode I loading [8][9][10].…”