Two-group, flux-coupled xenon oscillation model with an equation system of axial difference parameters

An axial xenon oscillation model is developed for pressurized water reactor analysis. The model employs an equation system for axial difference parameters that is derived from xenon and iodine balance equations coupled with two-group, one-dimensional neutron diffusion equations. To treat nonlinear xenon-flux-coupled terms, the spatial distributions of xenon, iodine, and flux are expanded by the Fourier sine series. The equation with respect to the axial difference parameters can be analytically solved with the initial condition related to axial power difference, which can be measured in the reactor. The axial power difference variation during xenon oscillation is directly obtained, and it provides a prediction of xenon oscillation behavior. The accuracy of the model is verified by benchmark calculations with a three-dimensional reference core calculation code and measured data from a core startup test at Yonggwang Unit 3.