Abstract
An evaluation method for reactivity feedback due to core deformation during reactor power increase in sodium-cooled fast reactors is being developed for realistic core design evaluation. In the core structural deformation analysis of the evaluation method, the fuel assembly bowing was modeled with a beam element of the finite element method. Assembly’s pad contact between adjacent assemblies was modeled with a dedicated element which could consider the wrapper tube cross-sectional distortion and the pad stiffness depending on pad contact conditions. A core support plate was modeled with a shell element to simulate the variation in pitch of fuel assemblies due to the thermal expansion of the core support plate. The fuel assembly bowing analysis model was verified for thermal bowing of a single assembly and assembly pad contact between adjacent assemblies in a 127-assembly core defined as past benchmark problems. The calculation results of displacements and pad contact loads by this model showed good agreement with those of reference solutions of theoretical solutions or results by participating institutions in the benchmark. This study proved that the analysis model was able to calculate displacements and pad contact loads appropriately.
