Improved Method for Calculation of Hannonic Modes for CANDU Reactors

Abstract

The higher harmonic solutions of the two-energy group finite difference neutron diffusion equations have a variety of applications in modal synthesis approximations of reactor flux distributions. These higher harmonics have been calculated by an extension of the successive overrelaxation iterative technique used for the solution of the finite difference equations.Ontario Hydro has developed a method of improving and extending harmonic modes calculated by this technique using a modal synthesis approach. This method can be used to improve the convergence and efficiency of calculation of a set of harmonic modes, and can be used to synthesize a new set of modes from an old set when some change has been made to the reactor model. This method has been applied to the calculation of sets of harmonic modes for several of Ontario Hydro's CANDU reactors.