Seismic Modelling of an AGR Nuclear Reactor Core

The work concerns the seismic response of an Advanced Gas-cooled Reactor (AGR) core. An LS-DYNA finite element model has been developed that represents each graphite brick. The contact between the bricks and their keys has been modelled with non-linear coaxial spring/dampers allowing for limited free motion. The model is a three dimensional representation of all the core layers and a neutron shield, making use of a symmetry by only modelling half of each layer. Different layers and groups of bricks have been allocated different spring/damper properties in order to accommodate differing initial geometry and levels of irradiation flux exposure. The core’s restraint system has also been modelled. Bespoke programs have been developed in Visual Basic for Applications to automatically generate the key file used by LS-DNYA and deal with the post-processing of results files. Sensitivity studies were done to assess the effects of changing the magnitude of the event and the effects of irradiation on the bricks.