MODELING FUEL ASSEMBLY DISTORTION IN LIGHT WATER REACTORS USING BISON

摘要

In this paper, bowing of a pressurized water reactorfuel assembly as a result of spatially asymmetric powerprofiles is analyzed using a beam representation of the3D fuel assembly. Past studies on this topic have focusedon the mechanical deformation of the fuel assembly withsimplistic modeling of the fuel rod elongation, which isthe major factor driving the fuel assembly bowing. In thisstudy, the beam representations of individual fuel rodsand guide tubes are coupled to corresponding 2Daxisymmetric models, simulated using the Bison code, tocapture all the intrinsic mechanisms that causeelongation of the fuel rod or guide tube. This study showsthat both the magnitude as well the shape of fuel assemblybow changes significantly with variations in the spatialpower profile and the fuel rod – spacer grid contactconditions.