DETAILED MODELLING OF THE EXPANSION REACTIVITY FEEDBACK IN FAST REACTORS USING OpenFOAM

摘要

The correct prediction of expansion-related reactivity feedbacks is paramount to the safetyanalysis of fast reactors. Traditionally, these feedbacks were evaluated via uniform radial andaxial expansions based on average diagrid and fuel temperatures, respectively. The resultingsmearing of the neutronic effects entails some limitations in terms of representation of localeffects and overall accuracy. In addition, the thermo-mechanical behavior of a core is acomplex phenomenon that cannot be reduced to simple uniform axial and radial expansions.Common examples of complex deformation patterns are the core compaction and the coreflowering, which are known to have potentially dramatic impacts on core safety. In this paper,a model is developed that allows for a detailed thermo-mechanical analysis of the core, andthat is capable of using this information for a locally detailed deformation of the geometryemployed in the neutronic model. The capabilities of the model are discussed, together withits present limitations and some needs for improvements.