Digital twin applications for seismic assessment of graphite reactor cores

The reactor cores of the Advanced Gas-cooled Reactors (AGRs) are made up of a large, three-dimensional array of interlocking graphite bricks. To assess the seismic performance of a wider range of reactor cores in a given condition (number, type, location and orientation of cracking of individual graphite components) that would be possible with physical testing, a computational model or digital twin has been developed. Cross-comparison of numerical simulations using this model and output from testing of a quarter-scale physical model have been used to validate the computational model, which has then been used to assess the behaviour of full-sized reactor cores during a seismic event. These assessments aim to demonstrate that the reactor cores can be shut and held down and adequate cooling of the fuel maintained during and after seismic events.