ENCORE - A Model of Reactor Core Configuration and Loads

摘要

Magnox and Advanced Gas-Cooled Reactor (AGR) graphite cores are constructed from columns of radially keyedgraphite bricks on a square lattice surrounded by a steel restraint cage. The bricks in the bottom layer of the core arespigotted to a steel diagrid below them. To enhance the understanding of the structural behaviour of the core a software code,ENCORE, has been developed to predict external brick forces and associated brick displacements for full-scale core models.ENCORE enables boundary conditions to be specified based on the effects of thermal expansion and contraction of therestraint cage relative to the diagrid, brick bow due to neutron irradiation and diagrid deflection. The model determines theequilibrium configuration of the core as that which minimises the total potential energy of the core.ENCORE has been proven to be an efficient, accurate and robust tool for core configuration modelling. Run timesare significantly less than for alternative finite element methods with solution times of the order several hours on a SUNUltra2 400MHz workstation for a three-dimensional model comprising 60000 bricks. ENCORE provides Magnox with thecapability to analyse full core configurations for the first time. In addition, by virtue of its fast execution time, it alsoprovides the ideal tool to build a full understanding of core behaviour under normal operation, transient or fault conditions.