The Development of a Physical Model of an Advanced Gas Cooled Reactor Core: Outline of the Feasibility Study

The graphite components in the Advanced Gas Cooled Reactor (AGR) cores are subject to degradation processes that are predicted to lead to greater numbers of weakened and cracked components. These ageing issues need addressing to maintain their safety and reliable operation, hence the requirement for the computer models of the cores used for the seismic resilience assessments to be conservative and to represent larger percentages of damaged graphite components. The current models have undergone limited experimental validation for high levels of degradation, so there is a need to validate those numerical models and also to enhance the understanding of core dynamics by physical modelling and testing. This paper outlines the feasibility study of a quarter scale model rig of an AGR core developed by the University of Bristol to provide validation to the computer models. The damage scenarios to be considered in demonstrating the core seismic tolerability were defined. Exploratory work on small arrays of components was carried out to inform the conceptual design of the rig components. The principles of scale modelling were put under scrutiny in parallel with several practical aspects of material selection and component design and manufacturing. Several variants of physical models of different size and shape were proposed and their merits with respect to their feasibility and outcomes were discussed. The phased decision making process that lead to the development of an 8-layer-20-bricks-across model is explained. Relevant aspects of instrumentation design and general requirements of dynamics and geometry are also presented.