Physical modelling and testing of an advanced gas cooled reactor core model

Advanced Gas Cooled Reactor (AGR) cores are multi-layered arrays of graphite components whose geometry and mechanical properties change under prolonged exposure to neutron irradiation. The presence of cracked components in the arrays later in their operational life may cause disruption of core geometry with implications for fuel cooling and control rod insertion in the event of a severe, but infrequent, seismic event. These ageing issues need addressing in both the computational and the physical models employed in the seismic resilience assessments. This paper presents a physical model with quarter-sized components of an array representative of those in AGR cores. The model was developed by the University of Bristol to provide experimental validation to computational tools which model high levels of core degradation. This paper outlines the principles of model design and the relevant aspects of rig development. The rig is tested on an earthquake simulator with the purpose to explore the mechanical interactions inside the array and to output acceleration and displacement data at selected locations. Relevant experimental outputs are presented showing dynamic responses of the array columns and top layer response maps. Overall, the model rig is capable of providing experimental evidence for the computational modelling methods, and so makes significant contributions to reducing uncertainties in these methods.