Dynamic fracture effects on remote stress amplification in AGR graphite bricks

Crump, Timothy; Ferté, Guilhem; Mummery, Paul; Jivkov, Andrey P.; Martinuzzi, Philippe; Tran, Van-Xuan

doi:10.1016/j.nucengdes.2017.01.014

Cited by 5 publications

(2 citation statements)

References 8 publications

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“…Furthermore, fast cracking at one keyway is anticipated to trigger a secondary crack at another, potentially opposite keyway, leading to brick disintegration. This phenomenon, known as prompt secondary cracking has been investigated in detail by dynamic fracture analysis, with results clearly confirming the anticipation (Crump et al, 2017;Crump et al, 2019).…”

Section: 𝜀 𝑡ℎ = 𝛼 ∆𝑇mentioning

confidence: 68%

Large-Scale Modeling of Damage and Failure of Nuclear Graphite Moderated Reactor

Farrokhnia

Jivkov

Hall

et al. 2022

Journal of Pressure Vessel Technology

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The UK Advanced Gas-Cooled reactors (AGRs) have cores made of graphite bricks with dual functions: as structural elements of the core, providing space for and separating fuel and control rods; and as moderator of the nuclear reaction. Nuclear graphite is a quasi-brittle material, where the dominant mechanism for failure is cracking. While cracking of isolated bricks is expected due to operation-induced changes in graphite microstructure and stress fields, these could be tolerated as far as the overall structural function of the core is maintained. Assessment of the whole core behaviour has been previously done with whole scale models where bricks have been considered as rigid body elements connected by elastic-brittle springs. This approach does not allow for the realistic assessment of the stresses in the bricks and associated brick cracking. Reported here are results from an ongoing project, which addresses this shortcoming. The proposed model uses deformable bricks with appropriate interactions, allowing for physically realistic whole core analysis. The results are focused on the damage that a graphite moderated reactor develops during a life cycle, how this affects the behaviour of the whole core, and how changes in bricks' behaviour impacts the core integrity. The proposed methodology is a major step towards high-fidelity assessment of AGRs' fitness for service, required for supporting continuous safe operation and life-extension decisions.

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Section: 𝜀 𝑡ℎ = 𝛼 ∆𝑇mentioning

confidence: 68%

Large-Scale Modeling of Damage and Failure of Nuclear Graphite Moderated Reactor

Farrokhnia

Jivkov

Hall

et al. 2022

Journal of Pressure Vessel Technology

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“…A full description of the function of each brick type and detail of the key–keyway system is provided in the second paper of Neighbour [ 2 ], ‘AGR Core Design, Operation and Safety Functions’. The AGR cores are now approaching the end of their design life [ 3 , 4 ], and in order to maintain safe operation, software tools are being used to assist in detailed analysis of the core components [ 5 , 6 ]. The safety case for each AGR facility includes consideration of the response of the nuclear reactor core to seismic events [ 7 ].…”

Section: Introductionmentioning

confidence: 99%

Design and Calibration of a Hall Effect System for Measurement of Six-Degree-of-Freedom Motion within a Stacked Column

Oddbjornsson¹,

Kloukinas

Gökçe

et al. 2021

Sensors

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This paper presents the design, development and evaluation of a unique non-contact instrumentation system that can accurately measure the interface displacement between two rigid components in six degrees of freedom. The system was developed to allow measurement of the relative displacements between interfaces within a stacked column of brick-like components, with an accuracy of 0.05 mm and 0.1 degrees. The columns comprised up to 14 components, with each component being a scale model of a graphite brick within an Advanced Gas-cooled Reactor core. A set of 585 of these columns makes up the Multi Layer Array, which was designed to investigate the response of the reactor core to seismic inputs, with excitation levels up to 1 g from 0 to 100 Hz. The nature of the application required a compact and robust design capable of accurately recording fully coupled motion in all six degrees of freedom during dynamic testing. The novel design implemented 12 Hall effect sensors with a calibration procedure based on system identification techniques. The measurement uncertainty was ±0.050 mm for displacement and ±0.052 degrees for rotation, and the system can tolerate loss of data from two sensors with the uncertainly increasing to only 0.061 mm in translation and 0.088 degrees in rotation. The system has been deployed in a research programme that has enabled EDF to present seismic safety cases to the Office for Nuclear Regulation, resulting in life extension approvals for several reactors. The measurement system developed could be readily applied to other situations where the imposed level of stress at the interface causes negligible material strain, and accurate non-contact six-degree-of-freedom interface measurement is required.

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A rate-dependent model and its user subroutine for cohesive element method to investigate propagation and branching behavior of dynamic brittle crack

Wang

et al. 2021

Computers and Geotechnics

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Dynamic fracture effects on remote stress amplification in AGR graphite bricks

Cited by 5 publications

References 8 publications

Large-Scale Modeling of Damage and Failure of Nuclear Graphite Moderated Reactor

Large-Scale Modeling of Damage and Failure of Nuclear Graphite Moderated Reactor

Design and Calibration of a Hall Effect System for Measurement of Six-Degree-of-Freedom Motion within a Stacked Column

A rate-dependent model and its user subroutine for cohesive element method to investigate propagation and branching behavior of dynamic brittle crack

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